Analysis for the development of legislation on child occupant

Transcription

Transport Research Laboratory
Analysis for the development of
legislation on child occupant protection
by M Hynd, M Pitcher, D Hynd, B Robinson and JA Carroll
(TRL)
CPR821
Specific Contract No: SI2.555655
Framework Contract No: ENTR/05/17.01
CLIENT PROJECT REPORT
Transport Research Laboratory
CLIENT PROJECT REPORT CPR821
Analysis for the development of legislation on child
occupant protection
by M Hynd, M Pitcher, D Hynd, B Robinson and JA Carroll (TRL)
Prepared for: Project Record:
Specific Contract No: SI2.555655
Framework Contract No: ENTR/05/17.01
Provision of information and services on the
subject of accident analysis for the
development of legislation on Child Occupant
Protection
Client:
European Commission, DG Enterprise and
Industry
(Peter Broertjes)
Copyright Transport Research Laboratory July 2010
This Client Report has been prepared for the European Commission, DG Enterprise and
Industry .
The views expressed are those of the authors and not necessarily those of the European
Commission.
Name
Date
Approved
Project
Manager
William Donaldson
19/07/2010
Technical
Referee
Mervyn Edwards
19/07/2010
Client Project Report
When purchased in hard copy, this publication is printed on paper that is FSC (Forest
Stewardship Council) registered and TCF (Totally Chlorine Free) registered.
TRL
CPR821
Contents
List of Figures
vi
List of Tables
ix
Executive summary
xii
1
Introduction
1
2
Project Objectives
3
3
Summary of Results
4
3.1
Collection of Market Research Information
4
3.2
Test Bench
3.2.1
Cushion
3.2.2
Anchorages
5
5
5
3.3
Front Impact
3.3.1
Pulse
3.3.2
Installation of CRS and dummy
3.3.3
Rearward facing integral restraints
3.3.4
Forward facing integral restraints
3.3.5
Non-integral restraints
6
6
6
6
7
8
3.4
Rear Impact
10
3.5
Side Impact
3.5.1
Test conditions
3.5.2
Reproducibility
3.5.3
Repeatability
3.5.4
Criteria
3.5.5
Friction of Anchorages
11
11
12
13
13
13
3.6
Dummies and Criteria
3.6.1
Biofidelity
3.6.2
Criteria
13
13
14
3.7
Implementation
3.7.1
Issues for consumers
3.7.2
Issues for CRS manufacturers
3.7.3
Issues for OEMs
14
14
14
15
3.8
Indication of costs and benefits
Option 2 – plus a side impact test
Option 3 – with a new, more representative frontal impact test
15
15
15
4
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Conclusions
17
4.1
Test Bench
17
4.2
Front Impact
17
4.3
Rear Impact
20
4.4
Side Impact
21
4.5
23
4.6
Implementation
23
4.7
24
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5
Recommendations
25
5.1
Test Bench
25
5.2
Front Impact
25
5.3
Rear Impact
27
5.4
Side Impact
27
5.5
Biofidelity and Criteria
28
5.6
Implementation
28
5.7
29
Acknowledgements
30
Appendix A
31
A.1
A.2
A.3
A.4
A.5
A.6
A.7
Appendix B
B.1
B.2
B.3
B.4
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Review of Accident Studies
Objectives
Types of accidents
General injury mechanisms in accidents
Front impact
A.4.1
Front impact accident severity
A.4.2
Body regions injured in front impacts
A.4.3
Injury mechanisms in front impact
Rear impact
A.5.1
Rear impact accident severity
A.5.2
Body regions injured in rear impact
A.5.3
Injury mechanisms in rear impact
Side impact
A.6.1
Side impact accident severity
A.6.2
Body regions injured in side impact
A.6.3
Injury mechanisms in side impact
Summary
A.7.1
Front impact
A.7.2
Rear impact
A.7.3
Side impact
Proposals for the New Procedures
Test Bench
B.1.1
Cushion Geometry
B.1.2
Cushion Material Properties
B.1.3
Co-ordinate System
B.1.4
Anchorages
B.1.5
Summary of anchorage locations
Front Impact
B.2.1
Test bench
B.2.2
Sled pulse
B.2.3
Test devices
B.2.4
CRS installation
B.2.5
Assessment criteria
Rear Impact
B.3.1
Test Bench
B.3.2
Sled pulse
B.3.3
Test devices
B.3.4
CRS installation
B.3.5
Assessment criteria
Side Impact
B.4.1
Test bench
ii
31
31
35
37
37
39
43
43
43
44
45
45
45
46
50
50
51
51
51
53
53
53
55
57
58
66
67
67
67
73
74
74
76
76
76
77
78
78
79
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B.5
Appendix C
C.1
C.2
C.3
C.4
C.5
C.6
Appendix D
D.1
D.2
D.3
D.4
Appendix E
E.1
E.2
E.3
TRL
B.4.2
B.4.3
B.4.4
B.4.5
B.4.6
Dummies
B.5.1
B.5.2
B.5.3
B.5.4
Door
Test devices
Intrusion
CRS installation
Assessment criteria
and performance requirements
Dummy design
EEVC Q-dummy injury criteria and performance criteria
GRSP informal group discussion on performance criteria
Bending moment – lateral bending
80
81
83
84
85
87
87
89
92
94
Practical assessment of proposed procedures
95
Introduction
95
Child restraint selection
95
Test Bench
97
Assessment of front impact proposals
99
C.4.1
Criteria Evaluation
100
C.4.2
Assessment of proposed protocols using an alternative pulse 112
C.4.3
Future work
121
C.4.4
Front impact summary
122
Assessment of rear impact proposals
124
C.5.1
Introduction
124
C.5.2
Effect of the proposed test bench
124
C.5.3
Evaluation of proposed dummy performance criteria
128
C.5.4
Rear Impact Summary
131
Assessment of side impact proposals
133
C.6.1
Introduction
133
C.6.2
Anchorages
133
C.6.3
Test conditions
133
C.6.4
Restraint system loading
137
C.6.5
Repeatability and reproducibility
143
C.6.6
Evaluation of proposed dummy performance criteria
147
C.6.7
The effect of varying friction in the ISOFix anchorages
155
Testing observations and possible restraint regulation nonconformities
D.1.1
Low rated restraint – IWH Babymax
D.1.2
High sales restraint – Maxi-Cosi Cabriofix
D.2.1
Low rated restraint – Nania Cosmo
D.2.2
High rated restraint – Maxi-Cosi Priorifix
D.2.3
High sales restraint – Bebe Confort Iseos
Forward facing non-integral restraints
D.3.1
Low rated restraint – Jane Monte Carlo
Side impact
Review of the Implementation Phasing of the new
Regulation
Introduction
Definitions
Implementation phases
E.3.1
Phase 1
E.3.2
Phase 2
E.3.3
Phase 3
158
158
158
158
158
158
159
159
159
159
159
160
160
160
161
161
162
162
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E.4
E.5
E.6
Approval routes
E.4.1
Single approval
E.4.2
Dual approval
Specific areas of concern
E.5.1
Semi-universal category
E.5.2
Vehicle specific category
E.5.3
i-Size
E.5.4
Labelling
E.5.5
ISOFix vehicle compatibility
Summary
Appendix F
F.1
F.2
F.3
F.4
F.5
F.6
163
163
164
169
169
169
169
169
170
171
Indications of the potential costs and benefits
175
Introduction
Casualty valuations
Options for assessment
F.3.1
Option 1 – Q series dummies, existing frontal impact test
F.3.2
F.3.3
Option 3 – with a new, more representative frontal impact
test
Target populations
F.4.1
GB casualty data
F.4.2
EU27 casualty data and estimates
F.4.3
EU27 Estimate Method 1 – GB data weighted by all road
user fatalities
F.4.4
EU27 Estimate Method 2 – GB data weighted by car
occupant fatalities
F.4.5
EU27 Estimate Method 3 – GB data weighted by EU18 child
car occupant fatalities and EU27 child road user fatalities
F.4.6
Summary of EU casualty estimates
Benefits estimate
F.5.1
Effects of previous legislative changes
F.5.2
Usage rates
F.5.3
F.5.4
F.5.5
Option 3 – with a new, more representative frontal impact
test
F.5.6
Summary of benefits estimates
F.5.7
Costs estimate
F.5.8
Market size
F.5.9
Marginal (per unit) costs to manufacturers
F.5.10
Summary of cost estimates
F.5.11
Benefit:Cost ratios
Summary
175
175
176
176
176
176
177
177
178
178
179
179
180
180
181
181
181
182
183
184
184
184
184
185
185
186
Bibliography
189
References
191
Regulations and Standards
193
GRSP Working Group documents
194
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List of Figures
Figure 1: European child fatalities 2005, Care database (n=585) .............................. 31
Figure 2: Distribution of accident type, GIDAS 1999-2009 data ................................ 32
Figure 3: Distribution of accident type, STATS19 1998-2003 data ............................. 32
Figure 4: Child casualties in cars by injury severity, STATS19 1998-2003 data ........... 33
Figure 5: Distribution of injury severity, per accident type, STATS19 1998-2003 data . 33
Figure 6: Distribution of accident type, FARS & NASS 1996-2005 data....................... 34
Figure 7: Relative risk of fatality for 0-7 year-olds (Viano, 2008) .............................. 34
Figure 8: Injury mechanism breakdown, GIDAS data 1999-2009 .............................. 36
Figure 9: Front impact change in velocity (reproduced from Cheung and Le Claire, 2006)
................................................................................................................... 37
Figure 10: All injured children on roads by posted speed limit CCIS data (reproduced
from Cheung and Le Claire 2006).................................................................... 38
Figure 11: Number of KSI children by road speed limit (N = 3,399) (reproduced from
Cheung and Le Claire 2006) ........................................................................... 38
Figure 12: Front impact child injuries (reproduced from Cheung and Le Claire 2006)... 39
Figure 13: Body regions to protect (reproduced from EEVC, 2008)............................ 40
Figure 14: Frequencies of injured body regions of children using CRS, Hannover data . 41
Figure 15: AIS 2+ injury distribution in front impact for children 6-12 years-old, CCIS
data ............................................................................................................ 41
Figure 16: Body region injury distribution of MAIS 2+ injuries in front impacts, NASS
1993-2007 data ............................................................................................ 42
Figure 17: Rear impact change in velocity (reproduced from Cheung and Le Claire 2006)
................................................................................................................... 44
Figure 18: CSFC-96 rear impact injury distribution (reproduced from EEVC, 2006)...... 44
Figure 19: Side impact change in velocity (reproduced from Cheung and Le Claire 2006)
................................................................................................................... 45
Figure 20: Children using CRS in side collisions on struck side (n=28) (reproduced from
Czernakowski, 2001) ..................................................................................... 46
Figure 21: Serious injury distribution for side impact, CIREN data............................. 47
Figure 22: CSFC-96 side impact injury distribution (reproduced from EEVC, 2006)...... 47
Figure 23: CREST accident database AIS 3+ side impact injuries (reproduced from EEVC,
2006) .......................................................................................................... 48
Figure 24: Frequencies of injured body regions of children using CRS, Hannover
University data ............................................................................................. 48
Figure 25: AIS 2+ injury distribution in side impact for children 6-12 years-old, CCIS
data ............................................................................................................ 49
Figure 26: Injury severity percentage for different amounts of side impact intrusion
(reproduced from Lesire, 2006)....................................................................... 50
Figure 27: Test bench mounted on a sled............................................................... 53
Figure 28: NPACS test benches............................................................................. 54
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Figure 29: Isometric view of the new regulation test bench cushions......................... 54
Figure 30: Dimensions of the new regulation test bench cushions ............................. 55
Figure 31: Drop test positions on the NPACS seat cushion........................................ 55
Figure 32: Bench co-ordinate system .................................................................... 57
Figure 33: 3rd ISOFix attachment point measurements ............................................ 60
Figure 34: Front impact test rig ............................................................................ 67
Figure 35: Euro-NCAP front impact test - 64 km/h, 40% offset deformable barrier test 69
Figure 36: R94 front impact test - 56 km/h, 40% offset deformable barrier test ......... 69
Figure 37: PDB front impact test - 60 km/h, 40% offset deformable barrier test ......... 69
Figure 38: Front impact average pulse comparison ................................................. 69
Figure 39: Euro-NCAP front impact test - 64 km/h, 40% offset deformable barrier test 71
Figure 40: PDB front impact test - 60 km/h, 40% offset deformable barrier test ......... 71
Figure 41: Front impact pulse comparison – R94 (56 km/h) & EEVC (60 km/h) test
pulses.......................................................................................................... 71
Figure 42: Front impact pulse............................................................................... 72
Figure 43: Rear impact sled ................................................................................. 76
Figure 44: Rear impact pulse................................................................................ 77
Figure 45: Original side impact test rig (CRS-14-4) ................................................. 79
Figure 46: Side impact test rig ............................................................................. 80
Figure 47: Test cushion dimensions....................................................................... 80
Figure 48: Door specification ................................................................................ 81
Figure 49: Side impact velocity corridor................................................................. 82
Figure 50: Original intrusion specifications ............................................................. 83
Figure 51: Intrusion depth measurements R95 tests (reproduced from ISO/PDPAS
13396, 2009) ............................................................................................... 84
Figure 52: Intrusion specifications evaluated by TRL ............................................... 84
Figure 53: Q-series instrumentation ...................................................................... 87
Figure 54: Q-series dummies ............................................................................... 88
Figure 55: Forward facing child restraints – head excursion...................................... 93
Figure 56: Rearward facing child restraints – head excursion.................................... 94
Figure 57: Seat foam impact responses for two sets of uncovered foam .................... 98
Figure 58: Seat foam impact responses for two sets of covered foam ........................ 99
Figure 59: Front impact test sled .......................................................................... 99
Figure 60: Proposed Deceleration Pulse Envelope, with deceleration pulses from the
experimental front impact testing...................................................................100
Figure 61: Scaling ratios used in the development of the head acceleration performance
thresholds ...................................................................................................103
Figure 62: Non-integral CRSs, dummy and belt interaction .....................................109
Figure 63: NHTSA vehicle accelerations, 50km/hr, 100% overlap barrier test ............112
Figure 64: Testing conditions using the higher pulse ..............................................113
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Figure 65: FMVSS 213 front impact pulse corridor, compared to new regulation pulse
corridors .....................................................................................................121
Figure 66: Rear impact test.................................................................................125
Figure 67: Test bench comparison .......................................................................127
Figure 68: P1.5 test comparison ..........................................................................127
Figure 69: TRL sled velocity data (28 tests) ..........................................................134
Figure 70: Dorel sled velocity data (6 tests) ..........................................................134
Figure 71: TRL sled deceleration data (28 tests) ....................................................135
Figure 72: Dorel sled deceleration data (6 tests)....................................................136
Figure 73: TRL sled deceleration data (6 reproducibility tests only) ..........................136
Figure 74: Anchorage displacement vs. initial distance between the door and the CRS in
the TRL test series........................................................................................142
Figure 75 – new Regulation implementation Phase 1 ..............................................162
Figure 78 – Three phases of the single approval option...........................................167
Figure 79 – Three phases of the dual approval option .............................................168
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List of Tables
Table 1. Summary of benefits and costs for each option .......................................... 16
Table 2: Injury mechanisms ................................................................................. 35
Table 3: Frequency of side impact angle ................................................................ 46
Table 4: Drop test matrix..................................................................................... 56
Table 5: Material properties of the test bench foam................................................. 57
Table 6: ISOFix anchorage locations...................................................................... 58
Table 7: Floor positioning versus H point ............................................................... 59
Table 8: X and Z coordinates of potential alternative 3rd attachment point (reproduced
from VTI, CRS-10-06).................................................................................... 60
Table 9: Top tether locations................................................................................ 61
Table 10: Belt anchorage locations........................................................................ 61
Table 11: Loads measured in anchorages Reg.44 pulse ........................................... 62
Table 12: Loads measured in ISOFix anchorages Euro NCAP pulse ............................ 63
Table 13: Loads measured in anchorages Reg.44 pulse ........................................... 64
Table 14: Loads measured in anchorages Reg.44 pulse, Euro-NCAP comparison ......... 64
Table 15: Anchorage loads during dynamic test ...................................................... 65
Table 16: Anchorage locations.............................................................................. 66
Table 17: Front impact pulse coordinates............................................................... 73
Table 18: Front impact deceleration sled requirements ............................................ 73
Table 19: Rear impact pulse coordinates................................................................ 77
Table 20: Rear impact deceleration sled requirements ............................................. 78
Table 21: Side impact velocity corridor coordinates ................................................. 82
Table 22: Side impact deceleration sled requirements ............................................. 83
Table 23: Q-series instrumentation ....................................................................... 88
Table 24: Q dummy performance criteria for 20% risk of AIS3+ injury (calculated using
logistic regression) ........................................................................................ 90
Table 25: Q dummy performance criteria for 50% risk of AIS3+ injury (calculated using
logistic regression) ........................................................................................ 90
Table 26: Q dummy performance criteria scaled from UNECE R94 adult performance
criteria......................................................................................................... 90
Table 27: AIS3+ 20% ......................................................................................... 91
Table 28: AIS3+ 50% ......................................................................................... 91
Table 29: Proposed dummy performance criteria .................................................... 92
Table 30: Rearward facing integral CRSs (Group 0+) short-list ................................. 96
Table 31: Forward facing integral CRSs (Group I) short list ...................................... 96
Table 32: Forward facing non-integral CRSs (Group II/III) short list.......................... 96
Table 33: CRSs selected to assess protocols........................................................... 97
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Table 34: Front Impact assessment matrix – rearward facing integral CRSs ..............101
Table 35: Scaling ratios used in the development of the head acceleration performance
thresholds ...................................................................................................102
Table 36: Front impact results table – rearward facing integral CRSs........................104
Table 37: Front impact assessment matrix - forward facing integral CRSs .................105
Table 38: Front impact results table – forward facing integral CRSs..........................106
Table 39: Front impact assessment matrix - forward facing non-integral CRSs ..........107
Table 40: Scaling factor ratio for the sternal deflection measurements .....................108
Table 41: Front impact results table – forward facing non-integral CRSs ...................110
Table 42: Front impact alternative pulse coordinates..............................................113
Table 43: Assessment Matrix to assess the effects of an alternative pulse .................114
Table 44: Stopping distance comparison ...............................................................114
Table 45: Higher pulse tests – Rearward facing integral CRSs..................................116
Table 46: Higher pulse tests – Forward facing integral CRSs....................................118
Table 47: Higher pulse tests – Forward facing non-integral CRSs .............................120
Table 48: Rear impact assessment matrix – test bench evaluation ...........................124
Table 49: Rear impact results table - test bench evaluation.....................................126
Table 50: Rear impact assessment matrix – test bench evaluation ...........................128
Table 51: Rear impact results table - criteria evaluation..........................................130
Table 52: Side impact anchorage locations............................................................133
Table 53: Summary of TRL test conditions and anchorage displacement ...................138
Table 54: Summary of TRL test conditions and anchorage displacement - rear facing
integral CRSs...............................................................................................138
Table 55: Summary of TRL test conditions and anchorage displacement - forward facing
integral CRSs...............................................................................................139
Table 56: Summary of TRL test conditions and anchorage displacement - forward facing
non-integral CRSs ........................................................................................139
Table 57: Anchorage displacement in the Dorel – forward and rearward facing integral
CRSs ..........................................................................................................140
Table 58: Test matrix for the assessment of repeatability and reproducibility ............143
Table 59: Repeatability results from the TRL sled tests ...........................................145
Table 60: Repeatability results from the Dorel sled tests.........................................146
Table 61: Reproducibility results for the sled tests with the Q1 dummy in a forward
facing CRS...................................................................................................147
Table 62: Reproducibility results for the sled tests with the Q1.5 dummy in a rearward
facing CRS...................................................................................................147
Table 63: Test matrix for criteria evaluation - rearward facing integral CRSs .............148
Table 64: Test results for criteria evaluation - rearward facing integral CRSs1 ............149
Table 65: Test matrix for criteria evaluation - forward facing CRSs...........................151
Table 66: Test results for criteria evaluation - forward facing CRSs1 .........................152
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Table 67: TRL Test matrix for investigation into the effects of increased friction on the
lateral movement of ISOFix anchorages ..........................................................155
Table 68: Test results for evaluation of the effect of friction 1, 2 .................................156
Table 69: Restraint type categories ......................................................................160
Table 70: Definitions ..........................................................................................161
Table 71: Reg.16 ISOFix size category .................................................................170
Table 72: Potential benefits and disbenefits if the proposed single approval or dual
approval routes are used...............................................................................173
Table 73: UK casualty valuations, 2008 (DfT, 2009)...............................................175
Table 74: Estimated EU casualty valuations...........................................................176
Table 75: GB casualty data, 2006-2008................................................................177
Table 76: Lower and upper annual GB casualty estimates, child car occupants <12 year
old .............................................................................................................178
Table 77: Lower and upper annual EU casualty estimates, child car occupants <12 years
old, Method 1 ..............................................................................................179
old, Method 2 ..............................................................................................179
old, Method 3 ..............................................................................................180
old .............................................................................................................180
Table 81: Step change effects in GB of previous legislative changes .........................181
Table 82: Likely casualty and monetary benefit estimates of option 1, EU27 .............182
Table 85: Summary of benefits and costs for each option .......................................185
Table 86: Summary of benefits and costs for each option .......................................187
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Executive summary
A Working Party on Passive Safety (GRSP), Informal Group on Child Restraint Systems
(“Informal Group”) was created by the World Forum for Harmonisation of Vehicle
Regulations (Working Party 29) on 16th July 2007. This Informal Group was tasked with
developing a new regulation for, ‘Restraining devices for child occupants of power-driven
vehicles’, for consideration by GRSP.
The aim is that this new regulation will include front, side and rear dynamic impact
assessments of Child Restraint Systems (CRSs) and will utilise a new family of child
anthropometric test devices (dummies) for acquiring measurements. The work of the
Informal Group is to be achieved in a number of steps, with the first phase to develop
performance criteria and test methods for ISOFix Integral “Universal” CRSs.
The Informal Group developed a number of proposals, for test methods for the new
regulation. However, the evidence base for some of these proposals was unclear and
hence the consequences of their potential implementation are not well understood.
The objective of this project was to assess the proposals made by the Informal Group
and to make recommendations for the way forward. The approach taken in this project
included a review of literature on accident studies involving children, to identify the
important body regions to protect, for each type of CRS and the associated injury
mechanisms.
This information was used in the subsequent dynamic test programme, which was
designed to assess the proposed procedures and to check that the dummies, proposed,
were suitable for recording the required measurements in the dynamic assessments.
The CRSs chosen for the practical assessment of the procedures were selected with
consideration to three different criteria; low reported rating in dynamic performance,
high reported rating in dynamic performance and high reported volume sales.
In total 21 front impact tests were conducted using the proposed pulse. The
measurements recorded in these tests were compared to the proposed injury criteria
limits. A further 6 front impact tests were conducted using a more severe pulse. This
pulse was created from an average of deceleration pulses from modern vehicles in a 50
kph 100% overlap test. The results from these tests were compared to those conducted
to the proposed pulse and the specified injury criteria limits.
A total of 11 rear impact tests were conducted using the proposed pulse with the Qseries dummies. In addition, tests using the P-series dummies were conducted to
understand the relative effect of the geometry and cushion properties on CRSs compared
to those of the test bench specified in UNECE Reg.44.
The project completed 34 side impact tests. The aims of these tests were to assess the
side impact procedure for repeatability and for reproducibility and to identify how it loads
restraint systems and how this relates the accidents in the real world. The criteria limits
set for front impact were assessed for their applicability to side impact assessment. In
addition to these assessments the affect of varying the friction of the sliding ISOFix
anchorages was evaluated. This limited investigation was designed to give an indication
of whether the level of friction allowable in the ISOFix anchorages warranted further
investigation.
The project went on to evaluate the implications of the three phases proposed for
implementation of the new regulation, for two scenarios; single approval and dual
approval of child restraint systems. The different approval routes and the issues arising
from them have implications for three key groups of stakeholders: consumers, CRS
manufacturers, and car manufacturers (OEMs).
A high level, indicative, cost-benefit analysis of the various regulatory proposals and
options has been carried out. It assumes that all children use CRSs and that they are
appropriate for the child and correctly fitted. The analysis draws together available
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information on European child car occupant accident statistics, along with more detailed
GB casualty data, and data gained on volume sales to provide an indication of the
possible likely costs and benefits of the new regulation.
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1
Introduction
Child occupant protection is currently legislated for by European Directive 2003/20/EC,
which states that occupants of motor vehicles must wear seat belts and children who are
under 12 years of age and below 1.5m in height must be seated in a child restraint. The
Directive currently allows countries to restrain children with the minimum height of
1.35m by the adult seatbelt; however, Germany, Italy, Austria, Ireland, Luxembourg,
Greece, Hungary, Poland and Portugal have enforced child restraint use under 1.50m.
The performance of the child restraint is legislated for by United Nations Economic
Commission for Europe (UNECE) Regulation No. 44, which specifies minimum
performance requirements for Child Restraint Systems (CRSs) used in power-driven
vehicles.
On 16th July 2007 the World Forum for Harmonization of Vehicle Regulations (Working
Party 29) agreed to the establishment of a new Working Party on Passive Safety (GRSP)
Informal Group on Child Restraint Systems (“Informal Group”). The remit of this Group is
to consider the development of a new regulation for, ‘Restraining devices for child
occupants of power-driven vehicles’, for consideration by GRSP. The aim is that this new
regulation will contain front, side and rear dynamic impact assessments and will utilise a
new family of child anthropometric devices for the assessment of the performance of
CRSs. The Informal Group was tasked to include, amongst others, the technical expertise
from European Enhanced Vehicles Committee (EEVC) Working Group (WG) 18, EEVC
WG12, ISO TC22/SC12 and NPACS as well as the results of discussions held in the
Informal Group and at GRSP. The work of this Group is to be achieved in a number of
steps with the first phase to develop performance criteria and test methods for ISOFIX
Integral “Universal” CRSs.
To date, the Group has developed a number of proposals for test methods for the new
regulation. However, the evidence base for some of these proposals is not solid and
hence the consequences of their potential implementation are not well understood.
Therefore a review of the available scientific evidence behind the test methods proposed
along with any additional supporting information is required in order to identify the
strengths and weaknesses of each proposal and make recommendations for the way
forward. In addition a review of the relevance of the performance criteria proposed for
use in these test methods is required, with particular consideration to the work of the
EEVC WGs 12 and 18 and the NPACS research for the new family of child dummies,
proposed for use in these test methods is required.
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Project Objectives
The objective of this project was to review proposals made by the GRSP Informal Group
and to make recommendations for the way forward.
The remit of the Informal Group is to consider the development of a new regulation for,
‘Restraining devices for child occupants of power-driven vehicles’, for consideration by
GRSP. The aim is that this new regulation will contain front, side and rear dynamic
impact assessments and will utilise a new family of child anthropometric test devices
(ATDs, or dummies) for the assessment of the performance of CRSs.
The TRL review includes assessments of:
•
How well the proposals will address the needs identified in accident studies;
•
The new dummy performance criteria and performance limits;
•
How the proposal would be implemented into regulation, i.e. how it would be
phased in;
•
Any potential unintended consequences;
•
Assessment of the practicality, repeatability and reproducibility of the favoured
side impact procedure;
•
Potential costs and benefits.
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3
3.1
Summary of Results
Collection of Market Research Information
This task involved the collection of Child Restraint System (CRS) market research
information to obtain an up to date indication of the best selling seat models sold in
Europe. The main purpose for this analysis was to inform the choice of CRSs to be used
in the practical assessment studies.
The market research information was obtained from the NPD Group, which is a global
provider of consumer and retail market research information for a wide range of
industries. They used a network of retail partnerships to obtain information for the UK
and France.
The information obtained provided the following:
UK Car Seats category:
•
Total Car Seats sales by month (in value and volume)
•
Category performance
•
Top 10 manufacturers groups
•
Top 10 brands
•
Top 10 products
•
ISOFix sales by month
Time period covered: January 2009 – December 2009
France Car Seats category:
•
Total Car Seats sales by month (in value and volume)
•
Category performance
•
Top 10 manufacturers groups
•
Top 10 brands
•
Top 10 products
Time period covered: July 2008 – June 2009
The information on market sales, market share and pricing information has been used to
help with providing information for the study of the ratio of benefit to costs of the
different proposals, detailed in Section Appendix F.
The information on sales figures for particular CRSs has provided information to help in
the selection of CRSs for the practical assessment, detailed in Section C.2. It was
important to include CRSs in our assessment programme that have had a high volume of
sales and hence, have a wide history of use in the European vehicle fleet. CRS models
generally have at least five years in the market before they are discontinued as a
product. By including these products it provides us with a certain level of confidence that
if these products are likely to cause injury to children in the way they provide restraint
under crash conditions, this will show up in the accident studies, in the body regions that
need to be protected.
In addition to the market research information, the dynamic performance of child
restraint systems, taken from various consumer testing schemes, was also considered
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when selecting the child restraint systems for the practical assessment programme. This
information was used to identify restraints in each group that were reported to have
poor or good dynamic performance (detailed in Section C.2).
3.2
Test Bench
The test bench consists of a seat frame and seat cushions, representing the back and
base of the vehicle seat, and the ISOFix and seat-belt anchorages
The current proposal for the test bench design is that it is to be based on the NPACS
frontal test bench. This was developed during the NPACS (New Programme for the
Assessment of Child restraint Systems) research phase.
3.2.1
Cushion
The original NPACS test bench designs used a different cushion design for ISOFix
attached restraints and belted seats. The test bench proposed for the new regulation has
a modified cushion to allow the attachment of non-integral ISOFix CRSs. The foam for
the proposed cushion to be used for the dynamic testing will have the same properties
as the foam used for the NPACS front impact test bench seat cushion (T75500 foam). It
seems reasonable that the cushions should be wider than the narrow NPACS cushion and
800 mm has been agreed.
The same cushion design will be used for in front and rear impact testing and a small
modification to the backrest cushion is required for side impact testing.
A preliminary foam specification has been proposed based on impact response corridors
constructed by TRL. Further work is required to define the cushion characteristics,
including:
3.2.2
o
The dataset should be enlarged with tests of other exemplar foam
cushions and new performance requirement should be generated from
these data.
o
It should be decided whether angled impacts are required in order to
adequately control the cushion performance.
o
It should be decided whether more than one impact speed is required in
order to adequately control the cushion performance.
o
Tolerances on the dimensions of the cushions should be agreed.
Anchorages
ISOFix anchorage locations have been proposed, based on those defined in NPACS,
which were based on the worst case geometries identified in the vehicles reviewed in
that project. The comparison data that has been presented to the Informal Group is
limited and there remains a compatibility issue for the use of non-integral CRSs in
vehicles with ISOFix anchorages that are off-set from the belt anchorages. This needs to
be addressed in Reg.14 if non-integral CRSs are to be approved as Universal.
An envelope for the alternative third attachment point must also be agreed for the test
bench and in Reg.14. ISOFix top tether locations and seat-belt anchorage locations have
been proposed based on those defined in NPACS.
Evidence has been presented to the Informal Group that the current Reg.14 anchorage
strength test requirements may be inadequate for some dummy and CRS combinations
allowed under the proposed i-Size categorisation scheme. This suggests that either the
ISOFix anchorage strength requirement in Reg.14 may need to change, or vehicles may
not be able to accommodate integral CRSs designed for older children. This is also
relevant for specifying the test bench for the new regulation, because the ISOFix mounts
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on the test bench must be strong enough for repeated testing and be of a size that is
representative of those used in cars.
It is recommended that an investigation is conducted with heavier occupants in front
impact tests under Reg.44 conditions (or the conditions agreed for the new regulation)
to investigate the increased anchorage loading. It is also recommended that comparative
tests are carried out to assess the relative effects of static (as used in Reg.14) and
dynamic loading (as applied in car crashes) to the vehicle anchorages.
3.3
3.3.1
Front Impact
Pulse
The pulse information presented to the Informal Group, for impacts at 50km/hr has been
based on 40% overlap offset frontal impact test data. This is in contrast to the Reg.44
pulse which was developed to represent full-width crash pulses, to encourage improved
occupant restraint systems. The objective of the offset frontal test was specifically to
encourage improved integrity of the passenger compartment of vehicles in order to
prevent serious crush injuries and to provide a survival space for the occupants.
Other regulatory regimes, such as FMVSS in the USA, require full-width car crash tests
and these are considered to be a more challenging test of the restraint systems in the
vehicle. The TRL project developed a crash pulse based on some full scale tests at
50 km/hr with a full-width barrier and compared CRS performance in tests at this more
severe pulse with tests to the current Informal Group proposal (see Section C.4.2).
It is recommended that the Informal Group decides which frontal impact configuration
would represent a better assessment of a restraint system, to be represented in the sled
tests. If the impact configuration is full-width, additional information on full-width vehicle
crash pulses will be required.
A parallel investigation would be worthwhile, into a pulse representative of modern
vehicles in the USA. The vehicle fleets in Europe and the USA have changed since the
development of R44 and FMVSS213 and there may be scope to harmonise these
requirements.
3.3.2
Installation of CRS and dummy
The installation of a CRS and test dummy in the new regulation is heavily based on the
procedures in the current Reg.44, with clarification in places. However some of this
process is open to interpretation, which can lead to inconsistency across Technical
Services.
3.3.3
The review of accident studies has shown that, for children injured in front impacts, the
head is the priority body region to protect. The majority of head injuries are caused by
contact with parts of the vehicle interior or other external objects.
The rearward facing integral CRSs passed all of the criteria proposed for the new
regulation. Head excursion is an important factor and the range of horizontal head
excursions were well inside the thresholds proposed for the dummies. Head excursion is
an issue for child protection in the field and therefore the performance thresholds for the
testing may need to be changed, to encourage less forward movement of these
products. The limit currently proposed is 700mm and the maximum forward excursion
across in the tests was less than 500mm.
These results, however, did not include any large rear facing CRSs and one could argue
that a larger CRS with a larger dummy would need more space. However, the space
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allowed for excursion should be based on the space available in the vehicle, which is
variable, and not based on dummy size. The value for head excursion should be
reviewed and based on the excursion space available to children in modern vehicles,
taking into account realistic vehicle front seat positions.
The values for the linear head acceleration thresholds have been taken directly from the
work of the EEVC Working Groups 12 & 18 (Wismans et al., 2008).
The composition of the scaling formula and the progression of the ratios for failure stress
and head length seem sensible. However, it may not be a realistic representation of
injury risk for children under the age of one. Therefore it is suggested that the head
acceleration threshold criterion for the different Q dummy ages needs to be reviewed.
The results of the assessment with the rearward facing integral CRSs at the higher pulse
showed that, with the exception of neck moments and chest compression, both of which
are well below the criteria limit, the other injury criteria significantly increased in
comparison to the tests using the proposed pulse.
As previously mentioned the main body region to protect for rearward facing restraints is
the head. This means head accelerations and excursions should be kept to a minimum.
The increase in pulse severity had a significant effect on the important body regions for
both of the dummies tested. The horizontal head excursions increased to exceed the
forward facing limit (550mm) with the larger dummy. However the effect on the smallest
occupant for this type of restraint (Q0) should also be evaluated prior to the changing of
any limits if this more severe pulse was to be adopted.
Head excursion is measured from the film of the test. In Reg.44 the testing laboratories
must apply procedures for estimating uncertainty of measurement (U of M) of the
displacement of the manikin's head. The confidence intervals should be specified and the
method of applying these confidence intervals to the U of M needs to be clearly defined.
It is not always possible to measure the head excursions using the side view of the test.
In some cases the top camera view has to be used. There are limitations with measuring
the excursions from the top view, as the dummy is constantly changing to a different
measurement plane during the test. The visual measurement alone, is incorrect and a
correction factor has to be applied. The correction factor is calculated by using results
from the tests where the difference between the measurement views is known. This is
also an issue for type approval and the assessment method should be defined more
clearly. The actual measured excursions must be known in order to carry out Product
Qualification testing and for Conformity of Production testing.
3.3.4
The review of accident studies indicated that head protection is the highest priority for
children travelling in forward facing integral CRSs, followed by chest protection. The
injury mechanism associated with these CRSs is head contact with parts of the vehicle
interior, so head excursion is the most important criteria. However in optimising a CRS
to achieve low head excursions, this can result in high head and chest accelerations, so it
is important to have a balance of performance across all three criteria.
All horizontal head excursions were both below the proposed limit of 550mm and below
500mm, the limit currently set for ISOFix integral restraints in Reg.44.
One CRS exceeded the threshold for head acceleration (by 1%), with the Q1 dummy.
The product performance ranged from 84%-101% of the limit for this criterion with the
Q1 dummy.
The product performance ranged from 97%-101% of the limit for vertical head excursion
with the Q3 dummy. This shows that the 800mm head vertical excursion limit is about
right for this type of restraint.
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From their use in the field, the CRSs tested in this programme are considered as
relatively safe with respect to the likelihood of neck injuries occurring in real world
accidents. However, in all the tests with the Q1 or Q3 in integral CRSs, the dummy
produced upper neck tensile forces which exceed the proposed threshold (they were on
average 149% of the threshold). This limit relates to an expected 50 % risk of AIS • 3
neck injury (as scaled for the child size; EEVC, 2008). Therefore it seems to be the case
that the proposed equipment, measurement tools or procedures do not lead to an
accurate assessment of injury risk for this body region.
The results of the assessment with the forward facing integral CRSs at the higher pulse
showed that the Q1 exceeds the HIC limit (150% of the limit), although there was no
head contact. The chest resultant criteria limit was exceeded (104%), as well as the
upper neck force (by 66%), which was also exceeded during the test with the proposed
pulse. In addition the head resultant acceleration reached 99%.
The Q3 exceeds the head vertical excursion limit as well as exceeding the limit of the
upper neck force, which was also exceeded during the test with the proposed pulse. In
addition, the chest resultant acceleration increased by 43% (to 91% of the limit) and the
head resultant acceleration increased by 19% (to 99% of the limit).
These results show that in addition to exceeding the neck force criteria limit, the criteria
limits of the important body regions, the head and chest were also exceeded. Although
the head horizontal excursions increased they are well below the limit. However the
larger dummy does exceed the vertical excursion limit.
3.3.5
Non-integral restraints
Head excursion is an important criteria for children restrained in non-integral CRSs. The
limit proposed for horizontal head excursion is 550mm. The head excursion results were
well below 500mm, so there is scope for reducing the threshold for horizontal head
excursion, in line with the space available in the vehicle.
The limits for chest compression were exceeded in the tests with the Q6 dummy. The
smaller dummies have greater thresholds than the larger dummies and it is unclear why.
The limits for chest compression were taken from the work of EEVC WGs 12 & 18
(Wismans et al., 2008), modified for the position of deflection measurement sensors. In
the threshold scaling, each of the material property parameters varies with age in a
sensible manner. However, the output of the scaling formula produces an unexpected
progression, where the sternal deflection for a one-year-old is greater than for an adult.
It seems unlikely that a one-year-old can sustain more sternal deflection than an adult
without injury. The scaling factor used related to the risk of rib fracture and did not
account for visceral injuries. Smaller children may sustain large thoracic deformations
before rib fracture occurs, however they may also sustain visceral injuries without rib
fracture. Therefore these scaling ratios are unsuitable for use in relation to all AIS 3+
thorax injuries to children, caused by restraint system loading to the chest. Chest
injuries are an issue for children in non-integral CRSs and the mechanism is associated
with the adult belt loading the chest. More research is needed in this area to set
appropriate thresholds for the criterion.
In addition to the head and chest region, the abdomen is also a high priority area to
protect for children using non-integral CRSs, however there is nothing on the Q dummy
that measures this. The injury mechanism associated with abdominal loading is
“submarining” and loading from the adult belt.
The kinematics of ISOFix attached non-integral CRSs can be different to the equivalent
belt attached systems and there is more potential for poor belt interaction and the
possibility of an increase in abdominal injuries. When the proposed procedures are
extended to include non-integral systems this will be a key area to monitor.
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The proposed procedures specify that a measure of abdominal penetration should be a
calculation of the forces measured in the lumbar spine and the lap belt. The suggestion
is that during the frontal impact the lumbar spine resultant of Fx and Fz shall not exceed
[undetermined] per cent of the lap belt force. From the results of the testing, it is
unclear what this measurement represents.
In all the tests with non-integral CRSs, the lap portion of the adult belt became wedged
into the gap at the top of the dummy legs. There are serious limitations with the ability
of the Q-series dummies to assess non-integral CRSs. It is essential that the lap portion
of the adult belt is able to take the path of travel over the dummy in the same way that
it would with a child. In addition to this the submarining motion should at least be
detectable and ideally should be measurable. For non-integral CRSs, where abdominal
injuries are a priority, the P series dummies, even with their limitations may be a better
option.
The CRSs tested in this programme are considered as relatively safe with respect to the
likelihood of neck injuries occurring in real world accidents. However, in all the tests with
the Q3 in the non-integral CRSs, the dummy produced upper neck tensile forces which
were on average 179% of the threshold. This limit relates to an expected 50 % risk of
AIS • 3 neck injury. Therefore it seems to be the case that the proposed equipment,
measurement tools or procedures do not lead to an accurate real world injury risk for
this body region.
The peak tensile forces measured at the lower neck are lower than those measured at
the upper neck. Therefore, if one was to assume a consistent injury threshold for tensile
force at the upper and lower neck, then the lower neck measurements would not provide
any additional information, when considering peak values. However research has shown
that for the older (> five months post-natal) cohort, the upper cervical spine is
significantly stronger then the lower cervical spine, which may support the
implementation of a lower neck tensile force threshold which is lower than the threshold
at the upper neck. In adults, the neck musculature adds greater force tolerance to the
lower neck than the upper neck and consideration of the cervical musculature would shift
the predicted site of injury (under tensile loading) from the lower to the upper cervical
spine. However, the effect of musculature on neck strength may be much less in the
necks of children. This research should be taken into account when proposing a tolerance
criterion for the lower neck.
No limit has been set for the upper neck extension moments. The work of Mertz et al.
suggested that the tolerance to extension moments was just over half of the flexion
values. Adopting an upper neck extension moment limit that was half of the flexion limit
would result in failures for some of the current CRSs tested with a Q1 dummy.
Therefore, the flexion to extension relationship for use with dummies representing small
children requires further investigation before it could be adopted.
Currently the lower neck does not have bending moment criterion in the new regulation.
The measured lower neck bending moment peak values are significantly higher than the
upper neck. This difference means if the criteria limits for the upper neck were applied,
these limits would be exceeded. Research has suggested that it may be appropriate to
multiply the upper neck threshold by a factor of two to generate bending moment IARVs
for the lower neck. If this approach was applied all of the CRS would pass the criterion.
However, the biomechanical basis for adopting such an approach is limited.
Some non-integral CRSs were assessed the higher pulse. The data show that as with the
test with the proposed pulse, the Q3 test exceeds the limit of the upper neck force with
the higher pulse. The Q3 dummy head and chest resultant acceleration remained the
same under both sets of conditions, close to the criteria limit (95% and 88%). However,
the head excursions of the Q3 increased by around 15%.
The Q6 exceeded the upper neck force criteria (115%) and continued to exceed the limit
of the chest compression (121%), as in the test with the proposed pulse. However, the
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Q6 results show a 15-25% increase in injury criteria results and a 5% increase in head
excursions.
The results show that the Q3 was not significantly affected by the increase in pulse
severity, with the same criteria exceeding the limits as the proposed pulse. The results
from the Q6 show a greater effect on the important body regions. The horizontal head
excursion limit could be revised as all dummies were well below the 550mm limit.
However it should be remembered that the largest dummy (Q10.5) was not tested, as it
is not currently available, and it is likely to have greater excursions. Though a different
head excursion limit could be set for this dummy, as in the current Reg.44.
3.4
Rear Impact
There is very little change in test conditions for rear impact between Reg.44 and the
proposed new regulation, other than the geometry and properties of the test bench. The
effects of these are reported in Section C.5.2. The rear impact test programme was
designed to assess the rear impact procedure proposed by the GRSP Informal Group.
The test conditions proposed remain the same as for Reg.44. The main differences
between UNECE Reg.44 and the proposal for the new regulation are the test bench and
the dummies. This rear impact test programme was designed to gain an understanding
of the relative effect of the geometry and cushion properties of the new proposed test
bench on the performance of CRSs and to assess the implications of using the Q-series
ATD criteria and limits, proposed by the Informal Group.
The review of rear impact accidents showed that a 30 km/h impact represents a large
proportion of rear impact accidents involving children, which supports the proposed test
conditions. The head was shown to be the priority body region for protection of children
in rear impacts. The injury mechanisms that cause these head injuries are not well
defined. Injuries to the neck and abdomen were also shown to be present, though these
only represented a small number of accident cases in the data analysis.
An assessment using the P series dummies was carried out to gain an understanding of
the relative effect of the geometry and cushion properties of the proposed test bench on
the performance of CRSs. The P-series dummy criteria were compared using the two test
environments and the limits specified in Regulation 44. The P0 represents a new born
child. It has no instrumentation and therefore the comparison is limited to the horizontal
and vertical head excursions.
The P1.5 was instrumented to the requirements of Regulation 44. Chest resultant and
chest vertical acceleration were compared using the instrumentation and potential
injuries to the head were compared by looking at the dummy head excursions.
The vertical excursion was seen to be less in the tests on the newly proposed test bench.
However, the proposed test bench allowed more rotation of the CRSs, towards the
seatback, allowing more movement of the dummy. The results showed increased
resultant and vertical chest accelerations. This may be due to the greater stiffness of the
proposed cushion and the increased angle of the backrest.
The new test bench cushion has been proposed as more representative of current vehicle
seats and with this being the case, it seems that the stiffness and the angles of the test
bench cushions have an effect on CRS performance. CRSs assessed on this new test
bench may, as a result, perform better over a wider range of vehicles.
The stiffer foam of the proposed test bench made it impossible to connect the ISOFix
attachments to the test bench anchorages, with one of the CRSs. The anchorages on the
test bench were moved forward to complete the test programme. If a CRS design is
incompatible with the new test bench, then it may have compatibility issues in the field.
The proposed test bench is more representative of modern vehicles and may therefore
provide a better assessment of the compatibility of CRSs in the field than the Reg.44 test
bench.
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An evaluation was carried out to assess the implications of using the Q-series ATD
criteria and limits, proposed by the Informal Group. As stated previously, the accident
review showed that the head is the priority body region to protect in rear impact. The
injury mechanisms that cause these head injuries in rear impact were not well defined.
The P0 dummy does not have the capability of measuring head acceleration and this is
not assessed in current type approval of CRSs. However, during this evaluation, two of
the CRSs tested with the Q0 dummy failed the limits proposed for the 3ms head
resultant acceleration requirement. If the Q series dummies were used as a
measurement device in type approval testing of CRSs, the head accelerations could be
assessed and this may lead to safer CRSs for young babies. The P0 has no capability to
measure chest acceleration and this is not assessed, with the smallest dummy, in
current type approval testing of CRSs. The resultant chest acceleration was on the limit
of the proposed criteria with the Q0 in the high rated CRS. Again, if the Q series
dummies were used in type approval testing and chest acceleration could be assessed,
this may lead to safer seats for new born children.
The tests where all three dummy sizes were assessed in the same CRS show that the
smallest dummy recorded the highest accelerations in the head, chest and pelvis, which
agrees with the philosophy that testing with the smallest dummy will be the worst case
test in terms of dummy loading. This suggests that type approving with the smallest
dummy instrumented could lead to safer CRSs.
Injuries to the neck were also found to occur in the rear impact review. The largest
dummy had the highest neck forces and moments, which is probably due to its larger
head mass. All the neck force and moment recorded values were well below the
proposed limits.
The accident review showed a very small number of abdominal injuries. It is not possible
to ascertain whether the CRSs protect the dummy from abdomen injuries in rear impact
using the current measurements available on the Q-series dummies.
3.5
Side Impact
The side impact procedure has been presented to the informal group on the basis that,
although the procedure is not representative of the real world accident, it is simple to
apply and it will improve the safety of CRSs. The practical assessment programme was
designed to assess the proposed procedure for repeatability and reproducibility.
The test procedure was assessed for repeatability based on three repeat tests of some of
the CRSs evaluated. Reproducibility of the test procedure was also evaluated by
comparison with the results of six side impact tests (three with a rear facing integral CRS
(Group 0+) and three with a forward facing integral CRS (Group I) at the Dorel test
facility in Cholet, France.
Furthermore, the procedure was assessed to evaluate the effect of applying the front
impact injury criteria to side impact and to evaluate, where possible, how the dummy
loading in the procedure relates to loading in the vehicle.
Finally, the effect of varying friction in the ISOFix anchorage, on dummy loading, was
evaluated.
3.5.1
Test conditions
The change of velocity was close to the middle of the target corridor for the TRL and the
Dorel tests, and the repeatability was very good. The reproducibility of the pulses
between the two laboratories was good. The range of TRL sled velocity was wider as it
contained tests carried out across a much wider range of CRSs.
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The TRL pulse is flatter and more consistent in the first 150 ms. The last part of the
pulse however, is slightly less consistent, about the time that the sled changes direction
to rebound. This part of the pulse partially overlaps the time frame during which the
resultant head accelerations reached their maximum value. However, the variation in
sled acceleration did not influence the repeatability of this measure.
The phasing of the loading to the CRS has an effect on the loading to the child. The side
of the struck vehicle is loaded by the striking vehicle and within 20ms the velocity of the
intrusion into the vehicle is in excess of 30km/hr. At this point the chassis velocity of the
struck vehicle is about 5km/hr. The chassis velocity of the struck vehicle builds relatively
slowly and the velocity of the intrusion slows down and meets the rising chassis velocity
at about 60ms. The proposed test procedure provides a good representation of the
speed of the struck vehicle chassis, however it does not reproduce the speed of the
intrusion into the struck vehicle.
Once loaded by the intruding structure, at no point does the vehicle seat lose contact
with the intruding structure. During the proposed test procedure the ISOFix anchorages
are allowed to move away from the intrusion panel. The phasing of the CRS-to-door
contact is different in the tests performed at TRL and Dorel and hence the maximum
resultant head and chest accelerations occur at different times.
3.5.2
Reproducibility
The impact velocity and stopping distance were very repeatable throughout the TRL
testing. A specification of 295 to 300 mm was used for calibration runs. Despite this, the
stopping distance in testing ranged from 293-305 mm, including five tests that exceeded
300 mm stopping distance and which would therefore have experience slightly greater
intrusion than was intended. The stopping distances in the TRL side impact tests would
easily have met a requirement of 300±10 mm. Nevertheless, the stopping distance may
be more critical for the side impact test procedure because it directly influences the
intrusion of the door. It is recommended that the tolerance on the stopping distance is
considered further, particularly with respect to the level of intrusion applied to the CRS.
The anchorage displacement in the side impact procedure was very variable. In the Dorel
tests the rear facing integral CRSs remained in contact with the intrusion panel, although
the anchorage displacement was considerably greater than in the TRL tests. The three
forward facing integral CRSs in the Dorel tests had very different anchorage
displacements and all three seats lost contact with the intrusion panel.
There was a considerable difference in the effective door intrusion between the Dorel and
TRL tests on the same CRS, due to differences in the lower anchorage performance.
The neck and pelvis measurements were generally much greater in the TRL tests than in
the Dorel tests. The anchorage displacement should be controlled to ensure consistent
loading of the CRS and good reproducibility of the test conditions.
In a vehicle it is possible that the out-board anchorage (nearest the door) could displace
as the vehicle seat is crushed, however it is unlikely that the inboard anchorage is likely
to displace substantially, thus limiting the displacement of the lower outer anchorage by
the amount that the CRS is crushed in the impact.
Many of the anchorage displacements observed in the tests were excessive, it is
recommended that consideration be given to limiting, and possibly eliminating,
anchorage displacement in the tests. Whether ISOFix anchorages move to the extent
that an ISOFix CRS will translate to the degree observed in these tests is questionable
and needs to be verified.
The real-world accident analysis showed that injury increased with increasing intrusion
and that this was the most important factor affecting injury outcome. However, the
reproducibility results show either no influence of intrusion, or a reduction of injury
measures with increasing intrusion, which is opposite to the real-world observation.
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The position of the CRS on the test bench was defined by measuring the distance from
the inner door trim to the centre of a CRS in a number of vehicles. Defining the initial
door position relative to the bench may encourage narrower CRSs that may perform well
in a test procedure and not so well in a small vehicle, which could then perform much
worse in a narrower car. The effect of CRS positioning with fixed anchorages should be
investigated, so that the test set-up represents the worst case scenario and CRSs cannot
perform artificially well.
3.5.3
Repeatability
ISO define good repeatability as a CV lower than 7%, and acceptable repeatability as a
CV lower than 10%, for all dummy performance criteria in certification and other test
procedures. The CV’s from the TRL and from the Dorel tests were generally well within
the acceptable range.
The peak values for the neck forces and moments in the forward facing seat, and the
pelvis acceleration in the rearward facing seat, were generally much higher in the TRL
tests. It was observed that the CRS typically moved away from the intrusion panel
relatively easily in the Dorel tests, but was driven sideways in the TRL tests.
3.5.4
Criteria
For children injured in side impact protecting the head is the main priority. Injuries to
the head are caused by contact with the vehicle interior or the intruding object. The head
was contained in all cases, however the resultant head acceleration limit was exceeded
in all tests. The injury criteria need to be set at a level that will improve CRS design. If
the proposed head criteria for front impact are applied to the side impact test procedure
it is likely to lead to CRSs that absorb the loading more effectively in lateral impacts.
Chest and abdomen account for a significant proportion of AIS 3+ injuries to children in
side impact. These injuries have been found to be caused by compression of the child by
the door panel of the vehicle. The chest compressions all passed the limits but the
resultant chest accelerations all failed. If the chest criteria proposed for front impact are
applied to the side impact test procedure it is likely to lead to CRSs that absorb the
loading more effectively in the chest area.
3.5.5
The amount of friction allowed in the ISOFix anchorages has an effect on the test
procedure. It is recommended that further investigation is carried out to allow the set-up
procedure to be more representative of the CRS when attached to anchorages in the
vehicle.
3.6
3.6.1
Biofidelity
For the dummy measurements to be valid, the dummy must interact with a restraint
system in a realistic way in order to display humanlike motion. This can only be achieved
if all parts of the dummy are biofidelic, because the behaviour of one body part can
influence another. For example, the motion of the head is influenced by the stiffness of
the neck and the torso. TRL compared the Q3 dummy measurements in quasi-static
tests with targets proposed in the literature (Visvikis et al., 2007). This revealed that the
Q3 did not meet all of its performance targets. The greatest deviations were found in the
chest and the shoulder. The chest was too stiff in both the front and side impact
directions, while the shoulder was too stiff to meet the side impact target. This needs to
be taken into consideration when using criteria limits that have been set by using scaled
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adult injury information. If these dummies prove to be the best current ATDs available, a
more pragmatic approach to assessment criteria and the associated limits may need to
be taken, based on the performance of CRSs with a known history in the field.
3.6.2
Criteria
The criteria that have been set have been assessed and discussed in the front, rear and
side impact sections of this report. The Informal Group has proposed that lower-neck
forces and moments, pelvis acceleration, lower-lumbar forces and moments, lap belt
forces (front impact), and head containment (side impact) should be assessed, but no
performance requirements have been either proposed or agreed for these
measurements. Furthermore, no procedure for assessing head containment in side
impact has been agreed for the draft new regulation.
3.7
Implementation
The project evaluated the implications of the three phases proposed for implementation
of the proposed new regulation, for two scenarios; single approval and dual approval of
child restraint systems. The different approval routes and the issues arising from them
have different implications for three key groups of stakeholders: consumers, CRS
manufacturers, and car manufacturers (OEMs).
3.7.1
It may be complex to understand the labelling and instructions, and how they apply to
particular vehicles. This is likely to be considerably more of a problem with dual
approval, which could require up to three sets of labels, multiple instructions and
multiple mass limits for a single CRS.
Car manufacturers will have to label which size of CRS and which CRS Regulation each
seating position is compatible with. This is likely to be very difficult for consumers to
understand and would apply for both single and dual approval routes.
Both routes lead to different types of restraint being approved to different Regulations at
different times, and therefore offering different levels of safety.
The potential combination of different vehicle seat labelling on each seat in multiple
vehicles; different CRS mass limits, CRS labels and instructions; and different approvals
for a single CRS is unlikely to reduce the already high incidence of misuse of CRSs.
3.7.2
For belt-attached integral or non-integral CRSs there is no difference between the single
and dual approval routes. It is not known how the belt-attached option would be
approved under the new Regulation once this becomes mandatory in Phase 3.
ISOFix integral CRSs - There is no obvious benefit to dual approval that would be
sufficient to justify the cost of meeting two sets of approval requirements and of
demonstrating conformity of production for both.
ISOFix-or-belt-attached integral CRSs - The most straightforward route is for
manufacturer’s to choose to continue to approve to Reg.44, because the alternative
requires multiple approvals and multiple CoP, as well as multiple labelling and
instructions which could be confusing to consumers and may therefore lead to an
increase in complaints and enquiries. The only obvious benefit to dual approval for this
CRS category would be if approval to the new Regulation was considered to be
prestigious. Overall, if Reg.44 is considered to be the more straightforward, lower-cost
option, CRSs may not be improved until Phase 3 is implemented, which will not
encourage design improvements in the short to medium term.
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ISOFix non-integral CRSs - It is not known how the belt-attached option would be
approved under the new Regulation.
3.7.3
Issues for OEMs
ISOFix or belt-attached integral CRSs - Car manufacturers will have to label the size of
CRS and the CRS Regulations that each vehicle seating position is compatible with
(Reg.14 and Reg.16 will need amending).
3.8
An indicative cost-benefit
been carried out. It draws
accident statistics, along
volume sales to provide
regulation.
analysis of the various regulatory proposals and options has
together available information on European child car occupant
with more detailed GB casualty data, and data gained on
an indication of the likely costs and benefits of the new
Three regulatory options have been assessed:
This option involves keeping the existing (UNECE Regulation 44) frontal impact test, but
replaces the P-series dummies with the more bio-fidelic Q-series devices, and makes use
of this enhanced bio-fidelity by setting performance criteria for the neck loadings and
chest compression. In terms of injury prevention, this option would thus help to reduce
neck and chest injuries in frontal impacts only. This option would also, it is assumed,
implement changes to the head excursion limits currently permitted, thus also helping to
prevent some head and face injuries in frontal impacts.
This option is the same as option 1 except for the addition of a side impact test
procedure (the existing regulation 44 has a frontal and rear impact impact test only).
This would thus have additional benefit (over and above Option 1) for casualties involved
in side impacts only.
The impact absorbing structures and occupant protection systems of cars have changed
radically over the last three or four decades. It is, therefore, unlikely that the crash pulse
(50 km/h frontal impact) used in the existing Regulation 44 (based on data from crash
tests carried out in the 1970s) is representative of crash pulses typically experienced by
occupants of modern vehicles. This option corrects this anomaly, and can thus be
expected to offer some additional casualty reduction benefit (over and above Option 1)
in frontal impacts only.
Three different methods of estimating the numbers of child (aged under 12) car
occupant casualties each year in the EU27 have been used, all based on applying
weighting factors to GB data. Applying casualty valuations to the overall range
estimated, also derived from GB data, indicates a societal cost of somewhere between
€2.5billion and €3.9billion per year.
Data from child restraint usage surveys and accident analyses are used to estimate that
50% of child car occupant casualties are from frontal impacts, 20% are from side
impacts, and to speculate that an overall future usage rate of 60% is a reasonable
assumption for the EU27. These data are combined with the measured casualty
reduction effects of previous legislative changes to produce EU27 estimates of the
benefits of the various options.
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Demographic data and information provided by the CRS industry are combined to
produce estimates of the likely costs (to consumers) of implementing the various
options, based on costs incurred by manufacturers for new product development and
testing.
Combining the benefit and cost estimates gives the overall ranges of estimated benefitcost ratios shown in Table 1.
Table 1. Summary of benefits and costs for each option
Option
Option 1
Option 2
Option 3
Benefits (€m)
Lower
Upper
48.7
69.7
66.3
97.2
96.0
140.1
Costs (€m)
Lower
Upper
4.7
16.8
14.2
28.0
18.9
55.9
Benefit:Cost ratios
Lower
Upper
2.9 :1
14.8 :1
2.4 :1
6.8 :1
1.7 :1
7.4 :1
These figures and ratios are necessarily based on various assumptions (described in
Appendix F) and are subject to considerable uncertainty. It is apparent, however, that
the broad indications from this study are that the benefit to cost ratios of all the options
being considered are likely to be positive, i.e. the benefits derived from reduced
casualties are likely to exceed the extra costs incurred by EU27 consumers, by a factor
of somewhere between 2 and 15 to one, depending on which option is chosen.
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4
Conclusions
4.1
Test Bench
The current proposal for the test bench design is that it is to be based on the NPACS
frontal test bench, developed during the NPACS (New Programme for the Assessment of
Child restraint Systems) research phase, with the following modifications:
•
The cushions should be wider than the narrow NPACS cushion and 800 mm has
been agreed.
•
The cushion should be the modified version that allows the attachment of nonintegral ISOFix CRSs.
•
The same cushion design will be used for in front and rear impact testing and a
small modification to the backrest cushion is required for side impact testing.
The foam for the proposed cushion will be the FTSS T75500 foam. Further work is
required to define the cushion characteristics, including:
•
The dataset should be enlarged with tests of other exemplar foam cushions and
new performance requirement should be generated from these data.
•
It should be decided whether angled impacts are required in order to adequately
control the cushion performance.
•
It should be decided whether more than one impact speed is required in order to
•
ISOFix anchorage locations have been proposed based on those defined in NPACS. The
data that have been presented to the Informal Group are limited and there remains a
compatibility issue for the use of non-integral CRSs in vehicles with ISOFix anchorages
that are off-set from the belt anchorages. This needs to be addressed in Reg.14 if nonintegral CRSs are to be approved as Universal.
An alternative third attachment point or volume must be defined for the test bench and
in Reg.14. ISOFix top tether locations and seat-belt anchorage locations have been
proposed based on those defined in NPACS.
The current Reg.14 anchorage strength test requirements may be inadequate for some
dummy and CRS combinations allowed under the proposed i-Size categorisation scheme.
The ISOFix anchorage strength requirement in Reg.14 needs to change, or vehicles may
not be able to accommodate integral CRSs designed for older children.
The ISOFix mounts on the test bench must be strong enough for repeated testing and be
of a size that is representative of those used in cars.
4.2
Front Impact
Test Conditions
The relevant pulse information presented to the Informal Group, for impacts at 50km/hr,
has been based on 40% overlap offset frontal impact test data, appropriate for
encouraging improved integrity of the passenger compartment of vehicles.
The Reg.44 pulse was based on full-width crash test pulses, appropriate for encouraging
improved occupant restraint systems within the vehicle.
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The pulse for the new regulation should be based on 50km/hr full-width crash test pulses
representing modern vehicles.
TRL carried out a limited study to develop a crash pulse based on some full-width crash
tests at 50 km/hr for comparison with the current Informal Group proposal.
Parts of the specification for installing the CRS and dummy on the test bench are open to
interpretation, which can lead to inconsistency across Technical Services.
Rearward facing integral CRSs
For children injured in front impacts, the head is the priority body region to protect. The
majority of head injuries are caused by contact with parts of the vehicle interior or other
external objects. Head excursion is an issue for child protection in the field.
The rearward facing integral CRSs passed all of the criteria proposed for the new
regulation, including the current head excursion limit of 700mm.
The maximum forward excursion in the tests with the rear facing integral CRSs was less
than 500mm.
The tests did not include any large rear facing CRSs, which may need more space.
The space allowed for excursion should be based on the space available in the vehicle,
which is variable, and not based on dummy size.
The values for the linear head acceleration thresholds may not be a realistic
representation of injury risk for children under the age of one.
The results with the rearward facing integral CRSs, at the higher pulse, with the
exception of neck moments and chest compression, significantly increased in comparison
to the tests using the proposed pulse.
The horizontal head excursions increased to exceed the forward facing limit (550mm)
with the larger dummy.
The increase in pulse severity had a significant effect on the important body regions for
both of the dummies tested.
displacement of the manikin's head. The confidence intervals are not specified and the
method of applying these confidence intervals to the U of M is not clearly defined.
In some cases the top camera view has to be used to measure the head excursions. The
visual measurement alone, is incorrect. This is a an issue for type approval as the
measured excursions must be known in order to carry out Product Qualification testing
and for Conformity of Production testing.
Head protection is the highest priority for children travelling in forward facing integral
CRSs, followed by chest protection.
The injury mechanism associated with these CRSs is head contact with parts of the
vehicle interior, so head excursion is the most important criteria.
Optimising a CRS to achieve low head excursions can result in high head and chest
accelerations, so it is important to have a balance of performance across all three
criteria.
All horizontal head excursions were below the proposed limit of 550mm and below
500mm, the limit currently set for ISOFix restraints in Reg.44.
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The product performance ranged from 84%-101% of the limit for head acceleration with
the Q1 dummy.
The product performance ranged from 97%-101% of the limit for vertical head excursion
with the Q3 dummy. This shows that the 800mm head vertical excursion limit is about
right for this type of restraint.
accidents.
In all the tests with the Q1 or Q3 in integral CRSs, the dummy produced upper neck
tensile forces which exceed the proposed threshold.
Therefore it seems to be the case that the proposed equipment, measurement tools or
procedures do not lead to an accurate assessment of injury risk for the upper neck force.
The forward facing integral CRSs were reaching or exceeding their limit for protection
when tested at the higher pulse.
The results with the Q1 in the forward facing integral CRSs, at the higher pulse,
exceeded the HIC limit, although there was no head contact. The chest resultant
acceleration limit was exceeded and the head resultant acceleration reached 99% of the
limit.
The Q3 exceeded the head vertical excursion limit, the chest resultant acceleration
increased by 43% (to 91% of the limit) and the head resultant acceleration increased by
19% (to 99% of the limit).
Head excursion is an important criteria for children restrained in non-integral CRSs. The
limit proposed for horizontal head excursion is 550mm. The head excursion results were
well below 500mm, so there is scope for reducing the threshold for horizontal head
excursion, in line with the space available in the vehicle.
The limits for chest compression were exceeded in the tests with the Q6 dummy.
The smaller dummies have greater thresholds than the larger dummies.
The limits for chest compression were taken from the work of EEVC WGs 12 & 18
(Wismans et al., 2008). The output of the scaling formula produces a sternal deflection
for a one-year-old greater than for an adult.
It is unlikely that a one-year-old can sustain more sternal deflection than an adult
without injury.
The scaling factor used related to the risk of rib fracture and did not account for visceral
injuries.
Smaller children can sustain large thoracic deformations before rib fracture occurs and
they can sustain visceral injuries without rib fracture.
The scaling ratios are unsuitable for use in relation to all AIS 3+ thorax injuries to
children, caused by restraint system loading to the chest.
Chest injuries are an issue for children in non-integral CRSs and the mechanism is
associated with the adult belt loading the chest.
More research is needed in this area to set appropriate thresholds for the criterion.
The abdomen is also a high priority area to protect for children using non-integral CRSs
and the injury mechanism associated with abdominal loading is “submarining” and
loading from the adult belt.
There is nothing on the Q dummy that measures “submarining”.
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There is more potential for poor belt interaction in an ISOFix attached non-integral CRS.
When the proposed procedures are extended to include non-integral systems this will be
a key area to monitor.
calculation of the forces measured in the lumbar spine and the lap belt. From the results
of the testing, it is unclear what this measurement represents.
There are serious limitations with the ability of the Q-series dummies to assess nonintegral CRSs. The lap portion of the adult belt must be able to take the path of travel
over the dummy in the same way that it would with a child.
Submarining motion should be detectable and ideally should be measurable. For nonintegral CRSs, where abdominal injuries are a priority, the P series dummies may be a
better option.
likelihood of neck injuries occurring in real world accidents. The proposed equipment,
measurement tools or procedures do not lead to an accurate real world injury risk for
upper neck loading.
the upper neck. Applying the same limits to the lower neck measurements would not
provide any additional information, when considering peak values.
For necks greater than five months post-natal, the upper cervical spine is significantly
stronger then the lower cervical spine.
In adults, the neck musculature adds greater force tolerance to the lower neck than the
upper neck.
Consideration of the cervical musculature shifts the predicted site of injury (under tensile
loading) from the lower to the upper cervical spine.
The effect of musculature on neck strength will be much less in the necks of children.
No limit has been set for the upper neck extension moments. The flexion to extension
relationship for use with dummies representing small children requires further
investigation before it could be adopted.
Some non-integral CRSs were assessed at the higher pulse. The Q3 dummy head and
chest resultant acceleration remained the same under both sets of conditions, however
the head excursions increased by around 15%.
The Q6 results show a 15-25% increase in injury criteria results and a 5% increase in
head excursions.
The horizontal head excursion limit could be revised as all dummies were well below the
550mm limit.
The largest dummy (Q10.5) is not currently available, and it is likely to have greater
excursions. A different head excursion limit could be set for this dummy, as in the
current Reg.44.
4.3
Rear Impact
There is very little change in test conditions for rear impact between Reg.44 and the
proposed new regulation, other than the geometry and properties of the test bench.
The main differences between Reg.44 and the proposal for the new regulation are the
test bench and the dummies.
conditions.
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bench.
The head was shown to be the priority body region for protection of children in rear
impacts. If the Q series dummies were used as a measurement device in type approval
testing of CRSs, the head accelerations could be assessed and this may lead to safer
CRSs for young babies.
Again, if the Q series dummies were used in type approval testing and chest acceleration
could be assessed, this may lead to safer seats for new born children.
test in terms of dummy loading. Type approving with the smallest dummy instrumented
could lead to safer CRSs.
4.4
Side Impact
apply and it will improve the safety of CRSs.
The practical assessment programme was designed to assess the proposed procedure:
•
For repeatability and reproducibility.
•
To evaluate the effect of applying the front impact injury criteria to side impact
•
To evaluate, where possible, how the dummy loading in the procedure relates to
loading in the vehicle.
•
To assess the effect of varying friction in the ISOFix anchorage, on dummy
loading.
Test conditions
The change of velocity was close to the middle of the target corridor for the TRL and the
Dorel tests, and the repeatability was very good.
The reproducibility of the sled velocity across the two laboratories was good.
The TRL pulse is flatter and more consistent in the first 150 ms. The last part of the
pulse however, is slightly less consistent, about the time that the sled changes direction
to rebound. The variation in sled acceleration did not influence the repeatability of the
head accelerations.
The proposed test procedure provides a good representation of the speed of the struck
vehicle chassis, however it does not reproduce the speed of the intrusion into the struck
vehicle.
Once loaded by the intruding structure the vehicle seat remains in contact with the
intruding structure. This is not reproduced by the proposed procedure, which allows the
ISOFix anchorages to move away from the intrusion panel.
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The phasing of the CRS-to-door contact was different in the tests performed at TRL and
Dorel and hence the maximum resultant head and chest accelerations occured at
different times.
Reproducibility
The impact velocity and stopping distance were very repeatable throughout the TRL
testing. The stopping distances in the TRL side impact tests would easily have met a
requirement of 300±10 mm.
The stopping distance may be more critical for the side impact test procedure because it
directly influences the intrusion of the door.
The anchorage displacement in the side impact procedure was very variable and not
reproducible across the two labs.
The CRS contact with the intrusion panel was variable not reproducible across the two
labs.
There was a considerable difference in the effective door intrusion between the Dorel and
TRL tests on the same CRS, due to differences in the lower anchorage performance.
The neck and pelvis measurements were not reproducible across the labs.
In a vehicle it is possible that the out-board anchorage (nearest the door) could displace
as the vehicle seat is crushed, however it is unlikely that the inboard anchorage is likely
to displace substantially, thus limiting the displacement of the lower outer anchorage by
the amount that the CRS is crushed in the impact.
Many of the anchorage displacements observed in the tests with the proposed procedure
appeared to be excessive.
and that this was the most important factor affecting injury outcome. The reproducibility
results show either no influence of intrusion, or a reduction of injury measures with
increasing intrusion, which is opposite to the real-world observation.
Defining the initial door position relative to the bench may encourage narrower CRSs
that may perform well in a test procedure and not so well in a small vehicle, which could
then perform much worse in a narrower car.
Repeatability
the acceptable range for repeatability within the respective labs.
Criteria
the head are caused by contact with the vehicle interior or the intruding object.
The head was contained in all cases, however the resultant head acceleration limit was
exceeded in all tests. If the proposed head criteria for front impact are applied to the
side impact test procedure it is likely to lead to CRSs that absorb the loading more
effectively in lateral impacts.
Chest and abdomen account for a significant proportion of AIS 3+ injuries to children in
side impact. If the chest criteria proposed for front impact are applied to the side impact
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test procedure it is likely to lead to CRSs that absorb the loading more effectively in the
chest area.
The amount of friction allowed in the ISOFix anchorages has an effect on the test results
and will contribute significantly to the effectiveness of the side impact procedure.
4.5
Biofidelity
system in a realistic way in order to display humanlike motion.
This can only be achieved if all parts of the dummy are biofidelic, because the behaviour
of one body part can influence another.
The Q dummy may not meet all of its performance targets, particularly in the chest and
the shoulder. The chest may be too stiff in both the front and side impact directions,
while the shoulder may be too stiff to meet the side impact target.
Criteria
The criteria that have been set have been assessed and discussed in the front, rear and
side impact sections of this report.
The Informal Group has proposed that lower neck forces and moments, pelvis
acceleration, lower lumbar forces and moments, lap belt forces (front impact), and head
containment (side impact) should be assessed, but no performance requirements have
been either proposed or agreed for these measurements. Furthermore, no procedure for
assessing head containment in side impact has been agreed for the draft new regulation.
4.6
Implementation
The project evaluated the implications of the three phases proposed for implementation
of the proposed new regulation, for two scenarios; single approval and dual approval of
child restraint systems. The different approval routes and the issues arising from them
have different implications for three key groups of stakeholders: consumers, CRS
manufacturers, and car manufacturers.
It may be complex to understand the labelling and instructions, and how they apply to
particular vehicles. This will be more of a problem with dual approval, which could
require up to three sets of labels, multiple instructions and multiple mass limits for a
single CRS.
Car manufacturers have to label the size of CRS and the CRS Regulation each seating
position is compatible with. This is likely to be very difficult for consumers to understand.
Both routes lead to different types of restraint being approved to different Regulations at
different times, offering different levels of safety.
The potential combination of vehicle seat labelling on each seat in multiple vehicles;
different CRS mass limits, CRS labels and instructions; and different approvals for a
single CRS is unlikely to reduce the misuse of CRSs.
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It is not known how the belt-attached option would be approved under the new
Regulation once this becomes mandatory in Phase 3.
There is no obvious benefit to dual approval of ISOFix integral CRSs to justify the cost of
meeting two sets of approval and conformity of production requirements.
The most straightforward route for ISOFix-or-belt-attached integral CRSs is for
manufacturer’s to choose to continue to approve to Reg.44. The only obvious benefit to
dual approval for this CRS category would be if approval to the new Regulation was
considered to be prestigious.
Issues for OEMs
Vehicle manufacturers, in consideration of integral CRSs that can be attached by ISOFix
or the adult belt, will have to label the size of CRS and the CRS Regulations that each
vehicle seating position is compatible with (Reg.14 and Reg.16 will need amending).
4.7
Option 1 involves keeping the existing Reg.44 frontal impact test, but replaces the Pseries dummies with the Q-series and sets performance criteria for the neck loadings and
chest compression. This option would help to reduce neck and chest injuries in frontal
impacts only. This option would also implement changes to the head excursion limits
currently permitted, thus also helping to reduce head and face injuries in frontal impacts.
Option 2 is the same as option 1 except for the addition of a side impact test procedure.
This would have additional benefit, over and above Option 1, for casualties involved in
side impacts only.
Option 3 is the same as option 2 with the addition of a more representative frontal
impact test.
The broad indications from this study are that the benefits derived from reduced
casualties are likely to exceed the extra costs incurred by EU27 consumers, by a factor
of somewhere between 2 and 15 to one, depending on which option is chosen.
The figures for costs and benefits and ratios are necessarily based on various
assumptions, as described in the main body of this report, and are subject to
considerable uncertainty.
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5
Recommendations
5.1
Test Bench
The proposal for the test bench design, based on the NPACS frontal test bench, should
be used, with the following modifications:
•
The cushions should be 800 mm wide.
•
The cushion should be the modified version that allows the attachment of nonintegral ISOFix CRSs.
•
The same cushion design should be used for in front and rear impact testing and
with a small modification to the backrest cushion for side impact testing.
Further work is required to define the cushion characteristics, of the selected foam (FTSS
T75500):
•
The dataset should be enlarged with tests of other exemplar foam cushions and
new performance requirement should be generated from these data.
•
It should be decided whether angled impacts are required in order to adequately
control the cushion performance.
•
It should be decided whether more than one impact speed is required in order to
•
A compatibility issue remains, for the use of non-integral CRSs in vehicles with ISOFix
anchorages that are off-set from the belt anchorages. This needs to be addressed in
Reg.14 if non-integral CRSs are to be approved as Universal.
The ISOFix top tether locations and seat-belt anchorage locations, for the test bench
should be based on those defined in NPACS. An alternative third attachment point or
volume must be defined for the test bench and in Reg.14.
The current Reg.14 anchorage strength test requirements may be inadequate for some
dummy and CRS combinations allowed under the proposed i-Size categorisation scheme.
It is recommended that an investigation is conducted with heavier occupants in front
impact tests under Reg.44 conditions (or the conditions agreed for the new regulation)
to investigate the increased anchorage loading. It is also recommended that comparative
tests are carried out to assess the relative effects of static (as used in Reg.14) and
dynamic loading (as applied in car crashes) to the vehicle anchorages.
The ISOFix mounts on the test bench must be strong enough for repeated testing and be
of a size that is representative of those used in cars.
5.2
Front Impact
Test Conditions
The pulse for the new regulation should be based on 50km/hr full width crash test pulses
representing modern vehicles, to provide an appropriate assessment of restraint
systems.
The vehicle fleets in Europe and the USA have changed since the development of R44
and FMVSS213 and there may be scope to harmonise these requirements. A parallel
investigation into a pulse representative of modern vehicles in the USA, would be
worthwhile.
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The specification for installing the CRS and dummy on the test bench should be clarified
to minimise misinterpretation, which can lead to inconsistency across Technical Services.
Rearward facing integral CRSs
For children injured in front impacts, the head is the priority body region to protect. The
majority of head injuries are caused by contact with parts of the vehicle interior or other
external objects. Head excursion is an issue for child protection in the field. The
horizontal head excursion limit should be revised to reflect the excursion space available
to children in modern vehicles, taking into account realistic vehicle front seat positions.
The values for the linear head acceleration thresholds should be revised, particularly for
the smaller dummies, where the thresholds may not be a realistic representation of
injury risk for children under the age of one.
Head excursion is measured from the film of the test. The testing laboratories must
apply procedures for estimating uncertainty of measurement (U of M) of the excursion of
the dummy's head. The confidence intervals should be specified and the method of
applying these confidence intervals to the U of M must be clearly defined.
In some cases the top camera view has to be used to measure the head excursions. The
visual measurement alone, is incorrect. The procedure for this should be clearly defined
in the proposal. These measured excursions must be known in order to carry out Product
Qualification testing and for Conformity of Production testing.
Head protection is the highest priority for children travelling in forward facing integral
CRSs, followed by chest protection. The majority of head injuries are caused by contact
with parts of the vehicle interior or other external objects. The horizontal head excursion
limit should be revised to reflect the excursion space available to children in modern
vehicles, taking into account realistic vehicle front seat positions.
The proposed equipment, measurement tools or procedures do not lead to an accurate
assessment of injury risk for the upper neck force. Neck injury is relatively rare, so the
majority of current products should pass any proposed criteria. Criteria for upper neck
protection should be devised to prevent new restraint designs that may lead to neck
injury.
Head protection is a high priority for non-integral CRSs. The horizontal head excursion
limit should be revised to reflect the excursion space available to children in modern
vehicles, taking into account realistic vehicle front seat positions. The largest dummy
(Q10.5) is not currently available, and it is likely to have greater excursions. A different
head excursion limit may need to be set for this dummy.
The limits for chest compression should be revised for all dummy ages to take into
consideration visceral injuries without rib fracture.
If the Q dummy is to be used for the assessment of non-integral CRSs it needs to be
modified to allow a “submarining” motion. In addition, the submarining motion should be
detectable and ideally should be measurable.
The P series dummy should be evaluated for it’s ability to assess forward facing nonintegral CRSs.
likelihood of neck injuries occurring in real world accidents. Neck injury is relatively rare,
so the majority of current products should pass any proposed criteria. Criteria for upper
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neck protection should be devised to prevent new restraint designs that may lead to
neck injury.
5.3
Rear Impact
in rear impacts.
It is recommended that, the proposed test bench is used for the assessment of rear
impact in the new regulation. It is more representative of current vehicle seats and with
this being the case, CRSs assessed on this new test bench may, as a result, perform
better over a wider range of vehicles.
The Q series dummies should be used as a measurement device in type approval testing
of CRSs, so that the head and chest accelerations could be assessed, which this may
lead to safer CRSs for young babies.
5.4
Side Impact
Test conditions
vehicle chassis, but it does not reproduce the speed of the intrusion into the struck
vehicle. In addition to this, at no point does the vehicle seat, to which an ISOFix seat
would be rigidly mounted, lose contact with the intruding structure. During the proposed
test procedure the ISOFix anchorages are allowed to move away from the intrusion
panel. The movement of these anchorages must be more controlled.
The phasing of the CRS-to-door contact is different in the tests performed at TRL and
Dorel and hence the maximum resultant head and chest accelerations occur at different
times. The phasing will be effected by the speed of the intrusion and the movement of
the anchorages on the test bench. If the ISOFix anchorages in the vehicle move, it is
likely to be worst case for the front passenger seat or the middle row of seats in an mpv.
This needs further validation with information from full scale testing.
Reproducibility
It is recommended that the tolerance on the stopping distance is considered further,
particularly with respect to the level of intrusion applied to the CRS.
The anchorage displacement should be considered further to maintain the relevant CRS
to intrusion contact conditions seen in the vehicle, to improve the reproducibility of the
procedure.
and that this was the most important factor affecting injury outcome. However, the
reproducibility results show either no influence of intrusion, or a reduction of injury
measures with increasing intrusion, which is opposite to the real-world observation.
When the anchorage displacement is revised the procedure needs to be validated to
check that the that injury measurements increase with increasing intrusion.
The position of the CRS on the test bench was defined by measuring the distance from
the inner door trim to the centre of a CRS in a number of vehicles. Defining the initial
door position relative to the bench may encourage narrower CRSs that may perform well
in a test procedure and not so well in a small vehicle, which could then perform much
worse in a narrower car. The effect of CRS positioning with fixed anchorages should be
investigated, so that the test set-up represents the worst case scenario and CRSs cannot
perform artificially well.
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Repeatability
the acceptable range.
As stated above, validation of the anchorage movement should address differences
between laboratories.
Criteria
The criteria will need to be reviewed when the movement of the ISOFix anchorages is
more controlled.
If the movement of the ISOFix anchorages can be controlled, such that the procedure
can reproduce the phasing of the loading events that is seen in the vehicle, albeit at a
lower severity through simplification of the procedure, it may be appropriate to adjust
the levels of the assessment criteria to compensate for the diminished loading. It is
recommended that further work is undertaken to assess this approach.
The amount of friction allowed in the ISOFix anchorages has an effect on the test
procedure. It is recommended that further investigation is carried out to allow the set-up
procedure to be more representative of the CRS when attached to anchorages in the
vehicle.
5.5
Biofidelity and Criteria
influence another. The Q dummy may not meet all of its performance targets. If these
dummies prove to be the best current ATDs available, a pragmatic approach to
assessment criteria and the associated limits will need to be taken, based on the
performance of CRSs with a known history in the field.
A procedure for assessing head containment in side impact must be agreed for the draft
new regulation.
5.6
Implementation
i-size adds to the factors that parents already need to take into account, when selecting
a CRS appropriate for their child and vehicle/seat. Whilst it adds new factors, it doesn’t
remove existing factors, i.e. the parent still needs to know the weight of their child. It is
recommended that the rationale behind the proposal to use i-size is reviewed. For both
approaches, and indeed for any conceivable approach, mass is required in order to
ensure that the CRS is not overloaded.
The implementation plan should be clarified. For example, the implementation section
assumes that the new regulation will come into force in three stages, as discussed in the
Informal Group. An alternative would be to fully develop the new regulation to include all
three stages before the regulation comes into force. The disadvantage to this approach is
that it will delay improving the performance of CRSs that have been selected
appropriately and used correctly by the consumer.
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5.7
The benefit to cost ratio calculated for the effectiveness of the new regulation assumes
that consumers will select appropriate CRSs and use them correctly, hence deriving the
full benefits of the improved CRSs. It is recommended that, when the specification for isizing is fully developed and the implementation route is clarified, the benefit to cost
ratio is recalculated to include issues associated with appropriate use and correct use of
CRSs.
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Acknowledgements
The work described in this report was carried out by the TRL Child Safety Centre of the
Transport Research Laboratory. The authors are grateful to Mervyn Edwards who carried
out the technical review and auditing of this report.
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Appendix A
Review of Accident Studies
A.1 Objectives
The review of accident studies was carried out with the main objective to identify the
injury mechanisms involved in front, rear and side impacts and to identify the body
regions that are important to protect for child vehicle occupants. In addition to this
information was gathered to gain a comprehension of side impact crash configurations
relative to the protection of children in restraints. Broader information about European
car occupant accident statistics for front, side and rear impacts was reviewed, with the
objective of providing information relevant to the study of costs and benefits, reported in
Section Appendix F.
A.2 Types of accidents
The CARE database contains the recorded child fatalities from road traffic accidents for
the majority of European countries. It should be noted that data from Germany is
missing from the database. Figure 1 shows that the largest proportion of fatalities occurs
in Spain, France, Italy and Poland with over 80 fatalities per annum. However it is also
important to remember that these data have not been adjusted to reflect the size of
population in these countries and these countries are among the largest in population
among Europe.
Figure 1: European child fatalities 2005, Care database (n=585)
The relative importance of front, side and rear impact protection for children has been
analysed frequently in recent years. Jansch et al. (2009) presented information from the
German In-Depth Accident Study (GIDAS). This database contains information about
vehicle accidents involving children in the areas around Dresden and Hannover. The
analysis covered a time period between July 1999 and July 2009.
Figure 2 shows that front impacts were the most common type of accident (37%)
involving children. Side impacts (20%), rear impacts (19%) and multiple impacts (23%)
were fairly similar in frequency. This suggests that, the new regulation may need to
consider including performance requirements for assessing child restraint systems in side
impacts. This is also dependent on the frequency and severity of injuries to children in
these accidents.
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Figure 2: Distribution of accident type, GIDAS 1999-2009 data
Cheung and Le Claire (2006) analysed STATS 19 data, which contained information of
road accident casualties from Great Britain. The study spanned the period between 1998
and 2003, covering 57,647 cases involving injuries to children under 12.
Figure 3 shows that front impacts again represent the largest proportion of accident
(50%) and although rear impacts (24%) account for a slightly larger proportion of
accidents than side impact (20%), protection of children in these accidents may need to
be considered.
Figure 3: Distribution of accident type, STATS19 1998-2003 data
The severity of the injuries to children in the STATS19 data for all types of accident was
also analysed (Figure 4). This shows that the large majority (94.1%) of children who are
injured in road accidents receive only slight injuries, with 5.6% being seriously injured
and less than 1% being killed.
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94.1%
0.3%
Slight injuries
Serious injuries
5.6%
Fatalities
Figure 4: Child casualties in cars by injury severity, STATS19 1998-2003 data
Cheung (2006) further analysed the STATS19 data to identify in which type of impacts
the different injury types were caused (Figure 5). This shows that all types of injuries are
caused in front impact accidents.
The GB data also showed that the proportion of children seriously injured is greater for
side impacts (21%) than for rear impacts (11%), even though they occur less
frequently. This also shows that of the children killed or seriously injured 57% occur in
front impacts. The figure shows that the proportion of side impact injuries increases as
the injury severity increases whether as the proportion of rear impact serious and fatal
injuries decreases.
Slight injuries (n=54,248)
Serious injuries (n=3202)
Killed (n=197)
Figure 5: Distribution of injury severity, per accident type, STATS19 1998-2003
data
A study by Viano et al. (2008) analysed 1996-2005 USA accident data from the Fatality
Analysis Reporting System database (FARS) and the National Automotive Sampling
System (NASS) crashworthiness data system. 5,219 road accident child fatalities were
found in the FARS database and 1,531,327 road accidents found in NASS database.
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These databases recorded impact angle of each of the vehicle collisions (Figure 6). This
shows that the proportions of side and rear impacts are similar to the GB 1998-2003
data. The proportion of front impacts has increased significantly, but this could include
multiple impact accidents, as this category does not exist in the database.
Figure 6: Distribution of accident type, FARS & NASS 1996-2005 data
Viano also used the data from FARS and NASS to calculate the fatality risk for each
seating position for each type of impact. The analysis showed that children travelling in
the second row (0.3%) have a 43% lower risk of fatality than the front row (0.53%) and
that the third row risk has an even lower comparative risk of fatality (0.22%).
Figure 7 shows the overall relative fatality risk for each seating position in the vehicle,
relative to the driver. This shows children in the second row were found to have 65-71%
lower risk of fatality than the driver.
Front
Row
Driver
(1)
2.44
0.54
Row 2
0.32
0.29
0.35
Row 3
0.21
0.33
0.16
Figure 7: Relative risk of fatality for 0-7 year-olds (Viano, 2008)
This agrees with the current recommendation that children should, where possible, be
restrained in the rear of the vehicle. However, the information also showed that, in the
second and third rows, children have a greater fatality risk from side impact than for
front impacts, compared to that of the driver. This again suggests the need to
incorporate a side impact test into the new regulation.
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A.3 General injury mechanisms in accidents
Child injury mechanisms were analysed by Jansch (2009) who presented information
from the GIDAS database, between July 1999 and July 2009. Table 2 shows the
documented injury mechanisms in the GIDAS database for each body region, however
they are not specific to front, side or rear impacts.
Table 2: Injury mechanisms
Head
Neck
Chest
Abdomen
Pelvis
Window Glass
A-B pillar
Body
Kinematics
Front seat
backrest
Body
Kinematics
Seat belt
Window Glass
B-C pillar
Seat belt
Rear seat
backrest
Seat belt
Front seat
headrest
Front seat
backrest
Rear seat
backrest
Rear side panel
Rear side panel
CRS
Body
Kinematics
Seat belt
Rear side panel
Loose Objects
Vehicle Roof
CRS
Figure 8 shows the proportion of each type of injury mechanism per body region for the
instances where injuries occurred. This shows that head injuries were caused by contact
with external objects. The seat belt is the predominate cause of chest, abdomen and
pelvis injuries. The kinematics of the occupant was the main cause of neck injuries and a
small proportion of chest and abdomen injuries.
Head
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Chest
Abdomen
Figure 8: Injury mechanism breakdown, GIDAS data 1999-2009
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A.4 Front impact
A.4.1 Front impact accident severity
Cheung and Le Claire (2006) reported on accident data from the Co-operative Crash
Injury Study (CCIS) database. This database was queried for the period between 1996
and 2004 for accident information involving all children under 12 years old.
The change in velocity for front impact accidents, where children were injured is shown
in Figure 9. This shows that 85% of front impacts where children are injured have a
change in velocity of less than 50 km/h.
Figure 9: Front impact change in velocity (reproduced from Cheung and Le
Claire, 2006)
Cheung (2006) also analysed the type of roads that children were injured using the CCIS
database. Figure 10 shows the proportion of injuries to children related to the speed limit
of the road on which the accident occurred. This shows that the largest percentage of
children injured in road accidents (52%) occur on roads with a speed limit of 30 mph (48
km/h).
Cheung analysed the data further to identify the road speed limit for the KSI casualties
(Figure 11). This shows that the highest proportion of KSI casualties occur on 30 mph
roads and 60 mph roads.
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Figure 10: All injured children on roads by posted speed limit CCIS data
(reproduced from Cheung and Le Claire 2006)
Figure 11: Number of KSI children by road speed limit (N = 3,399) (reproduced
from Cheung and Le Claire 2006)
Cheung (2006) also investigated the relationship between front impact severity and
injury from the CCIS data. From this Cheung presented Figure 12, which shows that for
front impact:
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50% of slight injuries occur at a change in velocity <35 km/h
•
90% of slight injuries occur at a change in velocity • 50 km/h
•
50% of serious injuries occur at a change in velocity • 50 km/h
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Figure 12: Front impact child injuries (reproduced from Cheung and Le Claire
2006)
A.4.2 Body regions injured in front impacts
Several previous European research projects have investigated, in detail, the priority
body regions for child injuries in front impact. The European Enhanced Vehicle-safety
Committee (EEVC) Working Group 18 Report: Child Safety - February 2006 (EEVC,
2006) produced a summary review of research from around Europe, combined with
analysis of accident database information with respect to child car occupants and
injuries.
The sources included:
•
International Road Traffic Accident Database (IRTAD) European accident data
•
National accident data from Germany, France, UK, Sweden, Italy and Spain
•
CREST (Child REstraint STandards)
•
CHILD (CHild Injury Led Design)
•
CCIS (Co-operative Crash Injury Study)
•
GIDAS (German In-Depth Accident Study)
•
Questionnaire study (UK),
•
CSFC 96 (LAB-CEESAR)
•
CASMIR (LAB-CEESAR)
This research concluded that the high priority body regions for each type of restraint, in
front impacts were as follows:
Group 0/0+ (Rearward facing)
For children travelling in rearward facing infant carriers severe head injuries were
found to be the most frequent injury. A high number of limb injuries were observed, but
these were thought to be less of a priority as they are less life threatening.
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Group I (forward facing)
Head injuries were found to be the most frequent injury sustained, by children
restrained in integral safety seats. The neck had a low frequency of injury, although it
was still deemed to be an area to protect. Chest and abdominal injuries were also found
to be not very frequent for children in integral safety seats.
Group II/III (booster seats or booster cushions with adult seat belt)
For children travelling on booster systems head injuries were again found to be the
most frequently injured body region and the importance of abdominal injuries
increased compared to integral restraints. Chest injuries were not very frequent, but it
was still deemed a priority body region because the chest provides protection to vital
organs.
Adult seat belt
For children restrained by the adult seat belt, it was reported that the body regions most
frequently injured were the same as for Group II/III booster systems, i.e. head
injuries. However this method of restraint resulted in higher severity injuries, especially
in the abdominal region.
The EEVC Working Group 12 & 18 Report: Q-dummies report - April 2008 (EEVC, 2008)
used the information from the EEVC WG18 Child Safety Report (2006) to produce
diagramic body regions to highlight the main areas that they considered needed
protecting in front impact, for the different types of child restraint (Figure 13).
This shows that the head is the priority body region to protect for all types of restraint.
The abdomen becomes a high priority with increasing age, where children progress into
non-integral restraint systems. It is questionable whether the neck should be a priority
body region as injuries to this body region were infrequent. The chest is well protected
for younger aged children using an integral restraint, but becomes a greater priority for
occupants using the adult seat belt.
Group 0/0+
Infant
Carrier
Group I
5pt Harness
Group I/II/III
(Harness Grp I,
Booster Grp II/III)
Group II/III
Booster Seat
Group II/III
Booster
Cushion
Adult Seat
Belt
Figure 13: Body regions to protect (reproduced from EEVC, 2008)
Czernakowski et al. (2001) conducted a study to investigate the affect of interface
conditions on injury severity of children in crashes. Information collected, from the
accident scene of 241 accidents involving children, by the Research Unit at Medical
University Hannover Germany, was analysed.
The distribution of injuries across all types of restraint, taken from the Hannover data is
shown in Figure 14. As with the EEVC report, this also shows that the head is the most
frequently injured body region. However this is followed relatively closely by chest
injuries.
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data
Visvikis et al. (2009) analysed the CCIS database for injuries to older children in front
impact as part of the EPOCh project. 277 cases, involving children aged 6-12 years-old
were identified. Of these, 15 accident cases, where the child occupant received AIS 2+
injuries, were analysed further. Figure 15 shows the injury distribution for the 15 cases
(18 injuries). This shows that the head, abdomen and upper limbs receive the largest
percentage of injuries. This agrees with the EEVC (2008) body region diagrams (Figure
13), showing that the main areas to protect for older children in front impact are the
head, abdomen and upper limbs.
Figure 15: AIS 2+ injury distribution in front impact for children 6-12 years-old,
CCIS data
The relationship between frequency of injury and severity of injury is also important.
Digges K, (2009) presented child injury data for front impact accidents, taken from the
NASS database between 1993 and 2007. Figure 16 shows the body region distribution of
MAIS 2+ injuries, for three different age groups.
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The report combines body regions into four bands, which makes it difficult to comment
on the individual body regions within the bands. For example, we know from the earlier
studies that the head is the most important body region to protect for all age groups.
However, the NASS combines head data with the neck data, giving the impression that
the neck is a high priority area, when the sample may in fact be mostly injuries to the
head. The band which includes the head, face and neck is the most frequently injured
body region in all three age groups.
For under 4 year-olds, where children a more likely to be restrained by an integral
restraint, the relative frequency of injuries to other body regions is low. However, the
frequency of injuries to the chest and limbs become more proportional with increase in
age group, where children are likely to be restrained by the adult belt or possibly on a
booster system. This information would agree with the EEVC (2008) body region
diagrams (Figure 13).
Figure 16: Body region injury distribution of MAIS 2+ injuries in front impacts,
NASS 1993-2007 data
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A.4.3 Injury mechanisms in front impact
EEVC (2006) investigated the mechanisms behind injuries to children, by reviewing
accident databases and previous research from around Europe. The EEVC concluded that
the mechanism behind the main injuries for each type of restraint was:
Group 0/0+ (Rearward facing)
In front impacts severe head injuries were found to be caused by either CRS impact with
the vehicle dashboard, direct impact of the head on a supporting object or during the
rebound phase. This latter mechanism was not specified any further, but it could mean
when the infant carrier rebounds after a front impact, the head may come into contact
with the restraint or vehicle seat.
Group I (forward facing)
In front impact, head injuries were found to be caused by direct contact between the
head and an object or were found to be diffuse brain injuries caused by angular
acceleration.
Group II/III (booster seats or booster cushions with adult seat belt)
In front impacts, head injuries were again found to be caused by head contact with the
vehicle interior. Abdominal injuries to the liver, spleen and kidneys were thought to be
caused by poor location of the lap section of the adult seat belt.
Visvikis (2009) used information from the CCIS database and the CARE database to
indentify the injury mechanisms behind the injuries to older children (6-12 years) in
front and side impacts.
Visvikis concluded that for front impact:
•
Head injuries are caused by direct contact with rigid parts of the vehicle interior
•
Abdomen injuries are caused by the child submarining under the lap section of
the seat belt
•
Chest injuries are caused by the diagonal section of the adult seat belt
•
Upper and lower limb injuries are caused by direct contact with parts of the
vehicle interior.
A.5 Rear impact
A.5.1 Rear impact accident severity
Cheung (2006) reported on the rear impact accident data from the Co-operative Crash
Injury Study (CCIS) database. The change in velocity for rear impact accidents, where
children were injured is shown in Figure 17. This shows that 45% of rear impacts that
cause injuries to children have a change in velocity between 25-29 km/h.
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Figure 17: Rear impact change in velocity (reproduced from Cheung and Le
Claire 2006)
A.5.2 Body regions injured in rear impact
The EEVC (2006) reported that the CSFC-96 database was the only information source
to provide a distribution of body region injuries in rear impact compared to the injury
risk per body segment for all types of child restraint (Figure 18).
The figure shows that the head is the most injured body region to be injured, followed by
limb injuries. Injuries to the chest and pelvis are very infrequent.
However it should be noted that this database only contained 83 rear impact cases, 60%
(50) of which sustained no injury. Of the 33 children who were injured 76% (25) had
slight injuries and only 24% (8) had severe injuries.
Figure 18: CSFC-96 rear impact injury distribution (reproduced from EEVC,
2006)
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A.5.3 Injury mechanisms in rear impact
The information about the injury mechanisms that cause injuries to children in rear
impact is limited. This is because European research programmes such as the CHILD
project and the NPACS project found the amount of serious injuries as a result of rear
impacts to be very low. The Great Britain STATS19 showed that there was around 354
KSI casualties cases (0.6% of total injuries) in rear impact and a further 13,500 cases
with slight injuries (23% of total injuries). The NPACS rear impact research (Cheung and
Le Claire, 2006) concluded that there were not enough cases in the field to require a
higher severity impact tests and as the Regulation test was deemed to be currently
suitable.
EEVC (2006) reported that it is most likely that the injuries to the head are cause by
similar mechanism to those that cause injuries to children in rearward facing Group 0+
restraints in front impact (A.4.3). The rear impact could cause the head of the child to
contact the vehicle interior or the restraint itself.
A.6 Side impact
A.6.1 Side impact accident severity
Cheung (2006) reported on side impact accident data from the Co-operative Crash
Injury Study (CCIS) database. The change in velocity for side impact accidents, where
children were injured is shown in Figure 19. This shows that 65% of side impacts that
cause injuries to children have a change in velocity of the struck vehicle chassis of
between 15-25 km/h.
Figure 19: Side impact change in velocity (reproduced from Cheung and Le
Claire 2006)
Czernakowski et al. (2001) plotted injury severity related to the struck vehicle delta-v
for side impacts using the data collected from 241 accidents by Hannover University. The
data shown in Figure 20 shows the trend that injury severity increases directly with the
delta-v. The proportion of MAIS 2-4 and MAIS 5/6 injuries begins to become significant
between 21-40 km/h.
The current proposed side impact test has a change in velocity of 26(+/-1) km/h, which
fits into this higher category, where severe injuries begin to occur in the field. However,
it has been well documented that the velocity of the intrusion of the vehicle structure
onto the occupants is greater than the change in velocity of the struck vehicle chassis.
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Figure 20: Children using CRS in side collisions on struck side (n=28)
(reproduced from Czernakowski, 2001)
Viano (2008) categorised the impact angle of accidents using 1996-2005 data from the
FARS database and NASS crashworthiness data system. Table 3 shows the frequency of
side impacts by angle, for this data.
This shows that around 60% of the side impacts occurred at around 60o impact and 30%
occurred at 90o impact angle. However, Viano found that the risk of fatality from a 90o
angled side impact (1%) was significantly greater than a 60o angled impact (0.1%), or a
120o impact (0.7%).
Table 3: Frequency of side impact angle
Impact angle
Cases
%
60/300
207,881
61%
90/270
102,787
30%
120/240
28,802
9%
(deg)
300 o
60o
270 o
90 o
240 o
120 o
A.6.2 Body regions injured in side impact
Brown et al. (2006) analysed data from the Crash Injury Research Engineering Network
(CIREN) database. The database contained 232 severe side impact injury cases (AIS
3+). Figure 21 shows the distribution of injuries per body region that was created from
the serious injury data.
This shows that injuries to the head are the most frequent AIS 3+ injuries (34%) in side
impact and are therefore the most important body area to protect. The chest region also
sustained a significant amount of AIS 3+ injuries (27%) followed by the abdomen
(17%).
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Figure 21: Serious injury distribution for side impact, CIREN data
The EEVC (2006) used the CSFC-96 database to create a body region injury distribution
for side impact, for all types of child restraint (Figure 22). This shows a similar
percentage of abdomen injuries to the CIREN data. There are more head injuries in the
sample and the percentage of chest injuries differs hugely between the two sets of data.
There were no pelvis injuries reported from the CSFC data.
Figure 22: CSFC-96 side impact injury distribution (reproduced from EEVC,
2006)
EEVC (2006) used side impact AIS 3+ injury data from the CREST project to create a
body region injury distribution for side impact (Figure 23). The accidents contained in
the CREST database are not representative of all accidents, as the project focussed on
the collection of data from more serious accidents only. This sample shows a much
larger proportion of head injuries compared to the CSFC and CIREN databases.
Chest and abdomen injuries are again shown to be important, with a small amount of
neck injuries, which corroborates the CIREN data.
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Figure 23: CREST accident database AIS 3+ side impact injuries (reproduced
from EEVC, 2006)
Czernakowski (2001) analysed the distribution of injuries in side impact, using
information taken from the Medical University Hannover Germany. The distribution of
injuries across all types of restraint, taken from the Hannover University data was shown
in Figure 24.
The struck side injury distribution shows that the head is the most frequently injured
body region (60%) and a priority for protection. The frequency of neck injuries from
these data was 20%. The injuries to children seated on the non-struck side of the vehicle
are predominately head injuries (75%), with 25% injuries to the upper limbs, though
there were only 15 cases in the database.
These data again show a high frequency of head injuries, as in the previous data, but a
proportion of neck injuries are also seen.
All restraint types, struck side
All restraint types, non-struck side
University data
Visvikis (2009) analysed the CCIS database for injuries to older children in side impact.
127 cases, involving children aged 6-12 years-old were identified. Of these, 5 accident
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cases where the child occupant received AIS 2+ injuries were analysed further. Figure
25 shows the injury distribution for the 5 cases (8 injuries). This shows that for older
children the head has the largest percentage of injuries, with significant injuries also to
chest, pelvis and lower limbs.
Figure 25: AIS 2+ injury distribution in side impact for children 6-12 years-old,
CCIS data
Lesire (2006) investigated the relationship between vehicle intrusion and injury severity
in side impacts, using accident data from the CREST and CHILD databases. The data
showed that vehicle intrusion has a direct influence on the severity of injuries to
children.
The data showed that for restrained children, seated on the struck side of the vehicle
where there was no direct intrusion, 81% received no injuries or slight injuries and few,
less than 14%, received serious injuries. Where direct intrusion was present, 33% of
children were uninjured or slightly injured, with a further 33% receiving moderate
injuries and 33% were seriously injured or killed.
The direct influence of intrusion on injury severity is further corroborated by the
breakdown of injury severity compared to maximum intrusion (Figure 26). The graph
shows that over 300mm intrusion will result in over 50% MAIS 4+ injuries for the
occupant. Below 200mm intrusion the MAIS 4+ percentage is less than 20%.
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100%
90%
80%
70%
60%
50%
MAIS 4+
40%
MAIS 2-3
30%
MAIS 0-1
20%
10%
0%
0-99
100-199 200-299 300-399 400-499
>500
Maximmum Intrusion (mm)
Figure 26: Injury severity percentage for different amounts of side impact
intrusion (reproduced from Lesire, 2006)
A.6.3 Injury mechanisms in side impact
Visvikis (2009) used information from the CCIS database and the CARE database to
indentify the injury mechanisms behind the injuries to older children in side impacts.
Visvikis concluded that for side impact:
•
Head injuries are caused by direct contact with rigid parts of the vehicle interior
or an intruding object
•
Chest and abdomen injuries are caused by compression of the child by the vehicle
door panel
•
Upper and lower limb injuries and pelvis injuries are also caused by contact with
the vehicle door panel
Lesire et al. (2006) conducted analysis of the CREST and CHILD accident data related to
side impacts. The injury causations for all children under 12 involved in side impact
accidents was investigated.
Lesire concluded that in side impact the injury causations for children on the struck side
of the vehicle were:
•
Head injuries are the most frequent injuries and occur due to head contact with
rigid parts of the vehicle interior
•
Chest and abdomen injuries are the next most frequently injured body regions
and occur due to compression through door panel contact
•
Upper limb injuries are more frequent for children using booster type restraints
and are also usually caused by door panel contact
•
Pelvis and lower limb injuries become sufficiently more frequent for children only
restrained by the adult seat belt as the is no protection from intrusion.
A.7 Summary
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Front impacts have been reported to be the largest proportion of accidents that result in
injuries to children (50%-60% of accidents). Rear impacts were reported to make up
14%-24% and side impact accidents were found to be 20%-26% of accident types. This
shows side impact accidents make up a significant percentage of accidents involving
children and therefore it is important that a side impact test procedure is included in the
new regulation.
A.7.1 Front impact
The front impact accident data showed that the majority of injuries to children occur in
accidents where the change in velocity is 50 km/h or less. The data has shown that 90%
of slight injuries and 50% of serious injuries to children occur below 50 km/h. The
STATS19 data also showed that the 94% of injuries to children in road accidents are only
slight injuries. This therefore shows that a 50 km/h test would represent a large majority
of accidents where children are injured. If only one front impact pulse is to be used to
assess the performance of CRSs, it needs to be carried out under these conditions. If a
test procedure was designed to optimise CRS performance only under the more severe
conditions, representative of half of the small number of serious injuries, it may lead to
stiffer CRSs, which may not perform so well in the majority of accidents where children
are being injured.
The data for children injured in front impacts has shown that the head is the priority
body region to protect. The majority of head injuries are caused by contact with parts of
the vehicle interior or other external objects. Chest and abdomen injuries become more
significant with increasing age of the occupant, along with pelvic injuries. Chest and
abdomen injuries were found to be predominately caused by the vehicle seat belt.
Protection of the neck was not shown, by the accident review, to be an issue. However,
it is important that any future changes in restraint design, associated with the new
regulation do not introduce an injury mechanism into an area that may be vulnerable.
Therefore it would be worthwhile providing a reasonable limit, reflecting the performance
of current CRSs, to criteria for the neck.
A.7.2 Rear impact
The rear impact change in velocity data has shown that a 30 km/h impact represents a
large proportion of rear impact accidents involving children.
The data for injuries to children in rear impact shows that the head is the priority body
region. The injury mechanisms that cause these head injuries are not well defined,
however it is presumed that these will be similar to those that cause injuries to rearward
facing children in front impact. Injuries to the neck and abdomen were also shown to be
present, though only a small number of accident cases were included in the data
analysis.
A.7.3 Side impact
The side impact data showed that the majority of injuries to children occur in accidents
where the change in velocity of the struck vehicle chassis was less than 25 km/h impact.
The impact angle analysis has shown that the largest proportion of side impacts occur of
at 60o, followed by 90o. However the risk of fatality for a 90o impact is significantly
greater.
Analysis of the injured body regions in side impact has shown that protecting the head is
again the main priority. Injuries to the head are caused by contact with the vehicle
interior or the intruding object. Chest, abdomen and neck injuries have been shown to
vary in importance between data sets. However, chest and abdomen account for a
significant proportion of AIS 3+ injuries to children in side impact. These injuries have
been found to be caused by compression of the child by the door panel of the vehicle.
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Appendix B
Proposals for the New Procedures
This section presents the proposals for new procedures tabled to the Informal Group with
any immediate comments, and identifies where this research programme may provide
some evaluation of the proposals. The proposals are described and the available
evidence base is presented. The section identifies some of the issues that need
clarification or further work and references work in the other parts of the report that may
address these issues.
The subjects covered in this section include:
•
The specification of the test bench, including cushion geometry, cushion material
properties, ISOFix and seat-belt anchorage locations, and ISOFix anchorage
strength
•
Front impact, including: the proposed sled pulse, additional requirements for
deceleration and acceleration sleds, CRS installation, and assessment criteria
•
Rear impact, including: the proposed sled pulse, additional requirements for
deceleration and acceleration sleds, CRS installation, and assessment criteria
Side impact, including: the proposed sled pulse, additional requirements for deceleration
and acceleration sleds, CRS installation, and assessment criteria.
B.1 Test Bench
The test bench consists of a seat frame and seat cushions, representing the back and
base of the vehicle seat, and the ISOFix and seat-belt anchorages. Figure 27 shows an
example of the front impact test bench mounted onto a deceleration sled. The following
sections define the geometry and material properties of the seat and backrest cushions,
the locations of the anchorages, and the results of investigations by the Informal Group
into the strength requirements for ISOFix anchorages.
Figure 27: Test bench mounted on a sled
B.1.1 Cushion Geometry
The current proposal is for the test bench design for all impact tests to be based on the
NPACS frontal test bench. This was developed during the NPACS (New Programme for
the Assessment of Child restraint Systems) research phase. The original NPACS test
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bench designs are shown in Figure 28. There was a different cushion design for ISOFix
attached restraints and belted seats.
ISOFix-attached cushion
Belt-attached cushion
Figure 28: NPACS test benches
During the NPACS validation phase (Cheung and Le Claire, 2006), it was recommended
that the width of the bench was extended to enable the testing of wider restraints, such
as carrycots, and the rear of the seat cushion was profiled to accept semi-universal
CRSs. The width of the bench has been extended to 800 mm and the cut-outs at the rear
of the cushion have been made so that restraints installed with ISOFix or the seat belt or
both can all be tested using the same cushion design (see Figure 29).
Figure 29: Isometric view of the new regulation test bench cushions
TRL (CRS-06-02) presented the extended-width NPACS test bench cushions
shown in
Figure 30. The cushion foam shall be covered by sun shade cloth made of poly-acrylate
fibre, the same as currently used for the test bench in Reg.44.
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Measurements ±2mm
Angles ±0.5o
Figure 30: Dimensions of the new regulation test bench cushions
B.1.2 Cushion Material Properties
The foam for the proposed cushion to be used for the dynamic testing will have the same
properties as the foam used for the NPACS front impact test bench seat cushion (T75500
foam). The properties of this cushion were chosen based on the results of head form
drop tests conducted on a series of different European M1 vehicles during the NPACS
project (Cheung and Le Claire, 2006).
TRL (CRS-03-05) presented the findings of this testing to the GRSP Informal Group, after
which these properties were accepted. Further reference to the drop test work conducted
by TRL during the NPACS project can be found in Annexe 12 of the NPACS Final Report
(Cheung and Le Claire, 2006).
TRL (CRS-09-09) conducted drop tests on the existing (narrow) NPACS cushions to help
the Informal Group characterise the T75500 foam to be used for the test bench. The
Reg.44 2.75 kg headform was dropped from three different heights (250 mm, 500 mm
and 750 mm) in three different positions on the cushion as shown in Figure 31.
Figure 31: Drop test positions on the NPACS seat cushion
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The Informal Group decided that, once the 800mm wide cushion was available, further
drop tests would be carried out by members of the Group. FTSS were asked to lead this
item and they have supplied a drop test method for assessing the dynamic properties of
the foam:
•
•
•
The tests should use the calibration set-up as defined in section 8.3 of Reg.44
o
2.75 Kg impactor (see annex 17 of Reg.44)
o
Drop height 500 mm
o
Three impact locations as defined in Reg.44 8.3.2
Three different configurations of the bench foam
o
Foam only, without cloth
o
Cloth wrapped around the foam but not glued to the bench
o
Cloth installed according to Reg.44 (glued to the bench)
Two angles for the bench foam
o
Bench laid down horizontally under 0•
o
Bench installed on sled under 15•
The test matrix proposed by FTSS is shown in Table 4.
Table 4: Drop test matrix
Bench angle
Cloth installation
0•
15• (on bench at
(horizontal)
sled)
Foam only
3 repeats
3 repeats
Cloth wrapped around foam
but not glued to bench
3 repeats
3 repeats
Cloth installed according to
Reg.44 (glued to bench)
3 repeats
3 repeats
TRL have contributed to the dataset by carrying out drop tests on two separate cushions.
These drop tests were out of the scope of this project; however, in order to consider the
test bench foam, the results from a number of these drop tests are analysed and
discussed in Section C.3. The material properties of the foam are shown in Table 5.
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Table 5: Material properties of the test bench foam
Density according to ISO 485 (kg/m3)
43
Bearing strength according to ISO 2439B (N)
p – 25 per cent
125
p – 40 per cent
155
Bearing strength factor according to ISO 3386 (kPa)
4
Elongation at rupture according to ISO 1798 (per cent)
180
Breaking strength according to ISO 1798 (kPa)
100
Compression set according to ISO 1856 (per cent)
3
B.1.3 Co-ordinate System
The co-ordinate system for the sled tests is defined according to SAE J211-1:Dec2003.
The co-ordinates system is defined relative to the bench seat for all front, rear and side
impact sled tests, and is therefore aligned with the vehicle that the test represents. This
gives a consistent co-ordinate system for front, rear and side impact bench tests, as well
as for front and rear impact tests of CRSs that are in the specific vehicle category that
are performed with a body on white mounted on the sled. No side impact test has yet
been defined for CRSs in the specific vehicle category, but the same co-ordinate system
would apply if such a test is developed.
The origin for the co-ordinate system is at the centre of the test bench cushion and on
the Cr line (the line where the seat back plane and seat cushion plane meet) as shown in
Figure 32.
Co-ordinate system
sits in the centre of
the test bench and on
the CR line
-y
-z
+x
Figure 32: Bench co-ordinate system
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B.1.4 Anchorages
B.1.4.1 ISOFix Anchorage Locations
TRL (CRS-05-03) presented the location of the ISOFix anchorages defined, for the front
impact test bench, in the NPACS project (Cheung and Le Claire, 2006) which have been
adopted in the current proposal for the test bench design. These anchorages represent
the location of the most rearward ISOFix anchorages in vehicles, based on
measurements data taken from 30 European vehicles. The most rearward position was
chosen as it is viewed to be the worst case position in terms of the compatibility and
dynamic assessment of ISOFix CRSs. The ISOFix anchorage locations are shown in Table
6.
Table 6: ISOFix anchorage locations
Location
x (mm)
y (mm)
z (mm)
Lower Left
-65
-140
-2
Lower Right
-65
140
-2
Only one set of comparison data has been presented to the Informal Group. MercedesBenz (CRS-03-06) investigated the location of the ISOFix anchorage bars in their current
vehicle range. They reported that:
•
In the x-axis, the bars ranged from 9-34 mm behind the CR line;
•
In the y-axis the modal anchorage position was 140 mm either side of the centre
of the CR line, although one vehicle did have offset anchorages (+125 mm and
-150 mm);
•
In the z-axis a large variation was observed ranging from -9 mm below to +6 mm
above the CR line.
These data show that the location of the ISOFix anchorages in the x-axis is very
rearward compared to the Mercedes-Benz vehicles. However the sample included only a
small number of vehicles (seven). The data also shows that there are vehicles where the
ISOFix anchorages are off-set to the belt anchorages. This may result in a compatibility
problem, where a restraint is installed into the ISOFix attachment points, but is then
unable to use the seat belt properly as it is offset of the ISOFix anchorages in the
vehicle, as it creates a poor fitment of the seat-belt across the occupant. There was a
large variation in the location of the anchorages in the measured z-axis. However, the
chosen z-axis location represents the median of the data from the measurements taken
during the NPACS research phase.
B.1.4.2 Alternative, third ISOFix Attachment Point
Reg.44 currently allows type approval of Universal ISOFix CRSs that are attached to the
vehicle by two lower rigid anchor points in addition to a top tether (third) anchorage
point, which acts as an anti-rotational device. The new regulation proposes to allow
ISOFix child restraints to be categorised as “universal”, with the use of an alternative
third attachment point as the anti-rotational device, namely a support leg. Therefore an
envelope for this 3rd attachment point will need to be defined in Reg.14.
The CRSs that use the alternative third attachment point will need an adjustable support
leg that is compatible with the envelope defined for Reg.14. The test bench that
assesses these CRSs will need to be adjustable to both ends of the range of movement
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of the foot. This option requires investigation into the range of floor depths in the current
European fleet.
TRL (CRS-05-03) presented the NPACS floor location which is the current proposal for
the test bench design. The floor specifications are:
•
210 mm below Cr axis (adjustable)
•
Surface hardness •120 HB, according to EN ISO 6506-1:1999
•
Surface roughness •Ra 6.3, according to ISO 4287:1997
•
Withstands 5 kN vertical concentrated load
o
Vertical movement •2 mm (relative to Cr axis)
o
No permanent deformation
The International Organisation of Motor Vehicle Manufacturers (OICA) (CRS-03-07)
presented data on their investigation into various floor positions. Measurements in the xdirection and z-direction were taken between the hip point and the heel point of the
adult male 50th percentile (J Male 50th percentile for superminis). The measurements are
shown in Table 7. It is unclear from the reference how many vehicles were measured
and how representative these measurements are of a wide variety of vehicles.
Table 7: Floor positioning versus H point
Vehicle Type
Average X (mm)
Average Z (mm)
Supermini
433
387
Small Family Car
537
359
Small MPV
515
394
Small Off-road
563
341
VTI (CRS-10-06) also presented information to the Informal Group, from measurements
of several vehicles with the aim of identifying a potential geometric zone, relative to the
present two rigid ISOFix anchorages, where an alternative third ISOFix anchorage may
be positioned.
A measurement fixture, based on the envelopes R2 (and R3) defined in ISO 132163:2006 (UNECE Reg.16 Annex 17) was used. The x and z coordinates were calculated to
provide these measurements relative to the centre line for the two rigid ISOFix
anchorages (Figure 33).
The measurements recorded during the study are shown in Table 8. VTI however
recognised that this sample was too small to draw any conclusions and therefore are
continuing to measure vehicles to add to these data.
It is clear that there is not yet enough VTI evidence to start creating a defined design
requirement for the 3rd attachment point at this point in time.
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Figure 33: 3rd ISOFix attachment point measurements
Table 8: X and Z coordinates of potential alternative 3rd attachment point
(reproduced from VTI, CRS-10-06)
Alternative 3rd
attachment point
coordinates
Measurements
Vehicle type
A
(mm)
B
(mm)
•
(deg)
•
(deg)
X
(mm)
Z
(mm)
MPV
495
440
11.9
90
-475
-294
Small family
565
410
10.8
90
-547
-260
Small family
545
330
10.8
89
-521
-184
Small family
535
250
10.8
80
-474
-102
Off-road
575
455
18.7
90
-530
-228
Off-road
590
480
18.7
86
-511
-247
Small family
550
465
16.4
90
-515
-267
Small family
575
420
16.4
85.6
-507
-213
Small family
590
330
16.4
84.2
-520
-119
Family
570
435
14.6
90
-540
-248
Family
570
340
14.6
86
-517
-152
Family
560
420
8.3
90
-548
-295
Family
580
300
8.3
83.7
-535
-170
The envelope for the alternative third anchor point is being led by OICA and is ongoing in
the Informal Group. The test bench floor will need to adjustable to the two extremes of
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anchorage position, so that Universal CRSs are designed to perform across a wide range
of vehicles.
B.1.4.3 ISOFix Top Tether Anchorage Locations
TRL (CRS-05-03) presented the location of the top tether anchorages from the NPACS
project (Cheung and Le Claire, 2006), which have been used in the current proposal for
the test bench design. These are the same locations as currently used in Regulation 44.
The top tether anchorage locations are shown in Table 9.
Table 9: Top tether locations
Location
X (mm)
y (mm)
z (mm)
Smallest dummy (G1)
-550
0
-475
Largest dummy (G2)
-1450
350
0
B.1.4.4 Seat Belt Anchorage Locations
TRL (CRS-05-03) presented the location of the seat belt anchorages from the NPACS
project (Cheung and Le Claire, 2006), which have been used in the current proposal for
the test bench design. These locations were chosen based on measurements taken from
the belt anchorage positions of the front and rear seats, of 30 different sized European
vehicles. The belt anchorage locations are shown in Table 10.
Table 10: Belt anchorage locations
Location
x (mm)
y (mm)
z (mm)
Upper (D-ring)
-240
-250
-630
Lower (buckle)
-29
200
59
Lower (outer)
10
-200
14.5
B.1.4.5 Seat belt Retractor
The seat belt retractor must be a diameter of 33 ±0.5 mm and be capable of locking
once the correct belt tensions have been achieved in the lap section (50±5N), shoulder
section (50±5N) and on the reel (4±3N).
B.1.4.6 i-Size ISOFix CRS Categorisation
“i-Size” is a category of CRS, for use in i-Size ready vehicles (not necessarily on all
vehicle positions) approved according to Reg.16 (Reg.16 will need to be amended). An i
-Size CRS must also meet some general requirements to make it suitable as an i -Size
CRS.
An i -Size CRS attaches to the vehicle by means of two rigid ISOFix attachments and an
anti-rotational device. The anti-rotational device is either a top tether or a connection
that attaches to the alternative third anchor point (yet to be defined). The dimensions of
an i -Size CRS are defined by the Vehicle Seat Fixtures (VSF) as defined in Regulation 16
as follows:
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i -Size forward facing integral CRSs must fit in ISO/F2x envelope dimensions for a
full-height forward-facing toddler CRS (height 720 mm) ISOFIX SIZE CLASS A (not yet
agreed). An integral CRS is where the child is restrained in the CRS independently of the
CRS to vehicle attachment. Non-integral i -Size CRSs have not been defined.
i -Size rearward facing integral CRSs must fit in ISO/R2 envelope dimensions for
a reduced-size rearward-facing toddler CRS ISOFIX SIZE CLASS D (not yet agreed).
The combined mass of an integral i-Size CRS plus the mass of the heaviest child
intended to use the CRS must not exceed 33 kg (not yet agreed).
B.1.4.7 ISOFix Anchorage Strength
The anchorages on the test bench must be strong enough to assess i -Size CRSs. With
the introduction of i -Size categorisation in the new regulation, the question whether an
older, heavier child can use an ISOFix integral CRS has been raised as this has
implications for the test bench and for UNECE Reg.14. The current specification in Reg.
14 relating to the ISOFix anchorages supplied in the vehicle was based on a child with a
mass of 18 kg in a CRS with a mass of 15 kg, giving a total mass for the CRS and
occupant of 33 kg. Currently a pair of ISOFix anchorages, in the vehicle, has to be
capable of withstanding a static load of 8 kN without deforming.
Members of the Informal Group from CLEPA and OICA have been investigating the effect
that different combinations of occupant and CRS mass, allowed within the proposed i Size categories, would have on ISOFix anchorage loads. To date, they have assessed the
effects of having different combinations of child verses product mass, within the overall
mass restriction of 33 kg, particularly looking at lighter CRSs with heavier occupants,
thus keeping the total mass the same.
DOREL Europe (CRS-03-17), for CLEPA, investigated the forces measured by the ISOFix
anchorages using different anti-rotational devices. Two different Group I ISOFix child
restraints with top tether were compared to a Group I child restraint with a support leg.
A rear facing Group 0+ ISOFix seat with support leg was also tested. Each seat was
subjected to a Reg.44 front impact pulse using the maximum sized dummy for the
restraint; P1.5 (11 kg) Group 0+, P3 (15 kg) Group I). The loads recorded are shown in
Table 11.
Table 11: Loads measured in anchorages Reg.44 pulse
Seat
Antirotation
Device
Total Mass
(seat
mass)
ISOFix
Location
(kg)
Left
Anchorage
Right
Anchorage
Top
Tether
(N)
(N)
(N)
Seat A
Top
Tether
26 (11)
Rear
2418
-
3870
Seat A
-
26 (11)
Rear
3468
-
-
Seat B
Top
Tether
24 (9)
Forward
1487
2387
3760
Seat B
-
24 (9)
Forward
2259
3497
-
Seat C
Support
Leg
29.6 (14.6)
Rear
3271
-
-
Seat D
Support
Leg
23.2 (12.2)
Rear
2928
4243
-
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The results show that, where measured, there was an imbalance between the left and
right ISOFix anchorages; however, the authors did question whether this was correct in
their conclusions. The imbalance may have been because the top tether was offset from
the centre line of the bench in the tests. The results also appear to show that the
addition of the top tether significantly reduced the loading on the ISOFix anchorages (by
43-52%), but cannot be used to show whether the support leg has a similar effect.
DOREL Europe (CRS-05-04) continued their work by investigating the loads on the
ISOFix anchorages using an ATD representing a 6 year-old child (P6), tested to a higher
severity pulse. A Euro NCAP type pulse was used to test a Group I integral child restraint
with and without a top tether anti-rotation device. All the tests were conducted using the
rearward anchorage position. The loads recorded in the testing are shown in Table 12.
Table 12: Loads measured in ISOFix anchorages Euro NCAP pulse
Total Mass
(CRS
mass)
Left
Anchorage
Right
Anchorage
Top
Tether
Antirotation
Device
Dummy
Reg.44
-
P3
24 (9)
2990
4685
-
Euro
NCAP
Top
Tether
P6
31 (9)
2878
?
5380
Euro
NCAP
-
P6
31 (9)
5198
?
-
Pulse
(N)
(kg)
(N)
(N)
These results show that the load on the anchorages measured in the test using the P6
without the top tether, were significantly greater than those with the P6 with a top
tether. The results with the P6 in a CRS with top tether at the higher pulse were
compared to tests with a smaller dummy (P3) in the CRS without a top tether, at a lower
pulse (Reg.44) and the loadings to the anchorages were still lower from the CRS with the
larger dummy (P6) and the top tether. This again shows that the addition of the top
tether, removes a significant amount of loading from the ISOFix anchorages. However,
the test with the P6 in the CRS without the top tether loaded over 10 kN through the
ISOFix anchorages, assuming symmetrically loading. However the Reg.44 test data
shows that the right anchorage experience 57% more load than the left and therefore
the anchorage total load in the P6 tests could have potentially been greater than just
double the load on the left anchorage.
Britax (CRS-07-02), for CLEPA, investigated the forces measured by the ISOFix
anchorages using Group I integral restraints with different anti-rotation devices. Three
different installation types of Group I ISOFix were tested: without an anti-rotation
device, with top tether, and with a support leg. Each seat was tested using the Reg.44
front impact pulse with the ISOFix anchorages in their rearmost position, and the force
on the left ISOFix anchorage was measured. The loads recorded in the tests are shown
in Table 13.
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Table 13: Loads measured in anchorages Reg.44 pulse
Total Mass
(seat
mass)
Left
Anchorage
Top
Tether
(N)
(N)
Rear
6729
-
27.1 (12.1)
Rear
3497
4528
P3
28.4 (13.4)
Rear
6287
-
Top
Tether
P3
23.7 (8.7)
Rear
3516
?
Seat C
-
P3
23.7 (8.7)
Rear
5334
-
Seat D
Support
Leg
P3
29.6 (14.6)
Rear
5157
-
Antirotation
Device
Dummy
Seat A
-
P6
34.1 (12.1)
Seat A
Top
Tether
P3
Seat B
Support
Leg
Seat C
Seat
ISOFix
Location
(kg)
The results showed that a 6 year-old in an integral ISOFix seat could result in 13.5 kN of
overall loading to the ISOFix anchorage points (assuming symmetrical loading),
compared with the 8 kN static load to which the anchorages are tested in Reg.14. Britax
commented that their connectors are therefore capable of handling this amount of force
as no sign of damage was seen during the tests. Britax also noted that the top tether
significantly reduces the loads in the ISOFix anchorages. The overall load to the ISOFix
anchorages, from seat B (> 12.5 kN) were also well above 8 kN (assuming symmetrical
loading). This suggests that either the ISOFix anchorage strength requirement in UNECE
Reg.14 may need to change or vehicles may not be able to accommodate integral CRSs
designed for older children.
DOREL Europe (CRS-07-03) conducted a comparison between the forces recorded at the
ISOFix anchorages in a Reg.44 impact test and those measured using a Euro-NCAP
frontal impact crash pulse. Two different restraint types were compared; a Group 0+
integral CRS (seat A) and a Group I integral CRS (seat B), both with support legs. The
maximum loads measured in the ISOFix anchorages during the tests are shown in Table
14.
Table 14: Loads measured in anchorages Reg.44 pulse, Euro-NCAP comparison
Seat
Antirotation
Device
Pulse
(kg)
Seat A
Support
Leg
Reg.44
Seat A
Support
Leg
Euro NCAP
Seat B
Support
Leg
Reg.44
Seat B
Support
Leg
Euro NCAP
TRL
Dummy
Total mass
(seat mass)
ISOFix
Location
Left
Anchorage
Support
Leg
(N)
(N)
P1.5
23.2 (12.2)
Rear
2847
3699
Q1.5
23.3 (12.2)
Rear
2968
3119
P3
29.6 (14.6)
Rear
3221
4065
Q3
29.2 (14.6)
Rear
3761
4622
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The results show that the forces in the anchorages of the forward facing seat (seat B)
significantly increase with the increase of test severity. However the rearward facing
infant carrier (seat A) is less affected by the increase in test severity.
JPMA and Vehicle Manufacturers LATCH Working Group (CRS-03-12) have investigated
the loads on the anchorages from three different types of CRS installation; LATCH, lap
belt only and 3pt seat belt. Each installation type was subjected to a 35mph frontal US
NCAP pulse with a Hybrid III 6 year-old (65 lbs, or 29.5 kg) and a child restraint (•21
lbs, or 9.5 kg) on the FMVSS213 test bench. The loads recorded in the tests are shown
in Table 15.
Table 15: Anchorage loads during dynamic test
Installation
Left
ISOFix
Anchor
(N)
Right
ISOFix
Anchor
(N)
Left
Lower
Anchor
(N)
Right
Lower
Anchor
(N)
Top
Tether
(N)
Shoulder
Belt
LATCH
8250
8500
-
-
10000
-
3pt Belt
-
-
8000
8250
7900
5000
Lap Belt
-
-
8500
8750
8750
-
This shows that the ISOFix anchorages received symmetrical loading with the top tether
receiving the largest proportion of the load.
Mercedes-Benz (CRS-06-03) investigated the relationship between the static strength
test of the ISOFix anchorages in a vehicle and the dynamic load they are subjected to
during a vehicle crash. The aim was to see whether it is possible to increase the
permissible mass of the child for the current anchorage systems. Currently:
•
In Europe, Reg.14 applies a static strength test with load level of 8 kN
•
In North America, FMVSS 225 applies a static strength test with load level of 15
kN
Mercedes-Benz attached a 40 kg force application device, which represented a 6 year-old
(30 kg) and a child restraint (10 kg) to the ISOFix and top tether anchorages in a
vehicle. The vehicle was then crashed according to US-NCAP, 56 km/h barrier with 100%
overlap. The results showed that anchorages deformed under the applied load.
Mercedes-Benz therefore recommended that as anchorages rated to 15 kN could only
just restrain the required level of force, the European anchorages would not be able to
due to their lower rating (8 kN).
The fact that the child is not perfectly coupled to the restraint also has to be considered,
i.e. an occupant and restraint mass of 25 kg and 10 kg does not give the same
anchorage forces as an occupant and restraint mass 20+15 kg, even though the total
mass is the same in each case. This means a 6 year-old in a light restraint will create
substantially larger anchorage loads, than the equivalent total mass combination of a 3
year-old and CRS (as shown by the P6 test data).
Some of the ISOFix anchorage load data show that the CRSs with support legs already
put in excess of 10 kN into the anchorages. Currently it is not known whether these
large restraints with support leg (typically around 15 kg) are causing anchorage failures
in the field as they have only been introduced to the market in the last few years.
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It is also very important to consider the relation between the tested static load of 8 kN
and the dynamic load. The duration of the recorded dynamic loading will be
comparatively shorter. It is recommended that further testing is carried out to assess
heavier occupants in front impact tests under Reg.44 conditions, to investigate the
anchorage loading. Also, it is recommended that comparative tests are carried out to
assess the relative effects of static and dynamic loading to the vehicle anchorages.
B.1.5 Summary of anchorage locations
The ISOFix and seat-belt anchorages for the impact testing are located at the positions
shown in Table 16, using the sign convention shown in Figure 32.
Table 16: Anchorage locations
Direction
x
y
z
Lower Left
-65
-140
-2
Lower Right
-65
140
-2
Smallest dummy (G1)
-550
0
-475
Largest dummy (G2)1
-1450
350
0
Upper (D-ring)
-240
-250
-630
Lower (buckle)
-29
200
59
Lower (outer)
10
-200
14.5
ISOFix anchorages
Top tether locations
Belt anchorage locations
1
Only tether point G1 is used for side impact
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B.2 Front Impact
The front impact test proposed in the new regulation is based on the Reg.44 front impact
test with some minor equipment and assessment changes.
B.2.1 Test bench
The test procedure uses the test bench and cushions described in Section B.1, the coordinate system defined in Section B.1.3 and the anchorage positions defined in Section
B.1.5. The TRL front impact sled test rig is shown in Figure 34.
Figure 34: Front impact test rig
B.2.2 Sled pulse
The question of which pulse to use in the front impact test was discussed during several
of the GRSP Informal Group meetings. The main reason for the discussion was to
ascertain whether the Reg.44 front impact pulse, which was created in the 1970’s and
based on vehicle data at the time, is still representative of modern vehicles. The Reg.44
front impact corridor was created from impact data from full width barrier, 50 km/h front
impact tests of a range of vehicles at the time. The design of vehicles has progressed
significantly since then, especially as the stiffness of vehicles has increased, firstly with
the introduction of the front impact test procedure in Reg.94 (56 km/h) and then with
the introduction of the higher severity Euro-NCAP test (64 km/h). Therefore it has been
suggested that the corridor may not be representative of the modern, stiffer vehicles.
Several pulses from front impact whole vehicle tests at different test speeds were
presented during GRSP Informal Group meetings. UTAC (CRS-04-03) presented the
vehicle pulses from three different types of impact, comparing each one to the current
Reg.44 corridor. Unfortunately the size, model or type of the vehicles tested and
presented to the Group are not known.
Figure 35 shows the vehicle pulses from nine different vehicles tested using the Euro
NCAP 64 km/h, 40% offset deformable barrier test. Comparing the average of the
vehicle pulses to the Reg.44 corridor shows that the initial deceleration gradient is not as
severe (steep) as the Reg.44 corridor. The initial gradient is less steep for the Euro NCAP
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vehicles even though they are much more recent designs than were used to define the
Reg.44 corridor, which is likely to be because the Euro NCAP data is from 40% overlap
offset frontal impacts, and the Reg.44 corridor is based on full-width impacts. Also the
peak, although outside the higher limit of Reg.44, occurs around 15ms later than the
Reg.44 corridor peak, at the point that the Reg.44 corridor is returning to zero, as the
impact sled would come to rest.
Figure 36 shows the vehicle pulses from eight different vehicles tested using the
Regulation 94 56 km/h, 40% offset deformable barrier test. Comparing the average of
the vehicle pulses to the Reg.44 corridor shows that the initial deceleration gradient is
not as severe (steep) as the Reg.44 corridor. Again, this is likely to be due to the
difference between full-width and offset frontal impacts. The peak does occur within the
Reg.44 corridor, but the deceleration decay then takes a longer time to reach zero, thus
increasing the stopping distance of a sled test.
Figure 37 shows the vehicle pulses from two different vehicles tested using a Progressive
Deformable Barrier (PDB), assumed to be a 60 km/h, 40% offset deformable barrier
test. Comparing the average of the vehicle pulses to the Reg.44 corridor shows that the
initial deceleration gradient is within the Reg.44 corridor until it drops below the lower
corridor just prior to the peak. The peak does occur around the maximum higher
deceleration limit of the Reg.44 corridor. The deceleration decay does match the
gradient of the Reg.44 corridor, however it is just beyond the outer limit of the corridor,
as the peak occurred towards the end of the higher corridor.
Figure 38 shows a comparison of the average pulses from Figure 35, Figure 36 and
Figure 37 with the Reg.44 corridor. This shows clearly that both the Euro NCAP pulse and
the R94 pulse do not match the current Reg.44 corridor very well and both would require
a longer stopping distance to be introduced as well as an increase in impact speed. The
PDB tests are the closest to fitting the corridor, however this pulse data is only based on
two vehicle tests, and the types of vehicles are unknown.
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Figure 35: Euro-NCAP front impact test - 64 km/h, 40% offset
deformable barrier test
Figure 36: R94 front impact test - 56 km/h, 40% offset
Figure 37: PDB front impact test - 60 km/h, 40% offset
Figure 38: Front impact average pulse comparison
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UTAC (CRS-07-07) presented some more vehicle pulses from three different types of
impact, showing a comparison of pulses from small vehicles to pulses from large
(referred to as “Berline” in the figures) vehicles, to the current Reg.44 corridor.
Figure 39 shows the vehicle pulses from four different vehicles (2 small, 2 large) tested
using the Euro NCAP 64 km/h, 40% offset deformable barrier test. The vehicle pulses
from the small vehicles show that the initial deceleration gradient is within the Reg.44
corridor, until the peak. However the peak occurs outside the corridor both in duration
and magnitude. The deceleration decay does then match the gradient of the Reg.44
corridor; however, it is just beyond the outer limit of the corridor. However, the larger
vehicles have an initial deceleration gradient which is not as severe (steep) as the
Reg.44 corridor. The peaks also occur later than required by the Reg.44 corridor and the
deceleration decay then takes a longer time to reach zero.
using a Progressive Deformable Barrier (PDB), 60 km/h, 40% offset deformable barrier
test. The vehicle pulses from the small vehicles show that the initial deceleration
gradient is within the Reg.44 corridor until the peak, which occurs earlier than the
Reg.44 corridor peak and with greater magnitude. The deceleration decay does then
match the gradient of the Reg.44 corridor. The larger vehicles have an initial
deceleration gradient also inside the Reg.44 corridor for the majority of the test and only
slightly exceed the Reg.44 maximum corridor at the peak. The deceleration decay does
match the gradient of the Reg.44 corridor, however it is just beyond the outer limit of
the corridor.
using the Regulation 94 56 km/h and the EEVC 60 km/h, 40% offset deformable barrier
tests. This shows that the increase in impact speed has little effect on the initial
deceleration gradient of all the vehicles. Two of the vehicles have little increase in the
maximum deceleration experienced by the vehicle between the two different test speeds.
However the other two vehicles (1 small, 1 large) see a 6-10g increase in peak
deceleration with increased impact speed.
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Figure 39: Euro-NCAP front impact test - 64 km/h, 40% offset
Figure 40: PDB front impact test - 60 km/h, 40% offset deformable
barrier test
Figure 41: Front impact pulse comparison – R94 (56 km/h) & EEVC
(60 km/h) test pulses
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The information presented to the Informal Group has shown that the Euro NCAP pulse
(64 km/h) would subject the restraint to a higher severity for a longer duration and is
therefore not representative of the Reg.44 pulse. The R94 pulse (56km/h) typically has a
less severe initial deceleration compared with the Reg.44 pulse, although the peaks have
a similar magnitude. The overall duration of the R94 pulse is similar to the upper limit of
the Reg.44 pulse. The information from the PDB pulses seems to show a similar severity
to the Reg.44 corridor. However this is only based on the data from four vehicles, and
there is a variation in pulse depending on the size of the vehicle.
Based on this evidence it was proposed by the Informal Group that the current Reg.44
pulse shown in Figure 42 will be used for the front impact testing. A valid calibration run
must be conducted before each set of testing which must meet the corridor and the
defined input criteria specified for deceleration devices (Table 18). Table 17 shows the
coordinates of the upper and lower corridors of the front impact pulse.
It was recognised that further investigation was required and this was added to the
scope of this project. The lack of information from 50 km/h, full width barrier tests,
needs to be rectified to allow a true evaluation as to whether the Reg.44 corridor is still
representative of modern vehicles to be conducted.
In order to investigate this further, an alternative pulse was developed within the project
based on full-width accident data available from NHTSA. This resulted in a pulse with a
higher peak deceleration and steeper initial deceleration than the Reg.44 pulse, which
was therefore very different to the offset pulses presented to the Informal Group and
summarised above. More discussion of this pulse and the results of tests using both the
alternative pulse and the standard Reg.44 pulse may be found in Section C.4.2.
Figure 42: Front impact pulse
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Table 17: Front impact pulse coordinates
Time
(ms)
Deceleration
Deceleration
lower corridor upper corridor
(g)
(g)
0
20
0
10
-
50
20
28
65
20
-
80
-
28
100
0
-
120
-
0
In addition to this, as part of this project, information from full scale testing has been
reviewed to provide evidence for an alternative front impact pulse. This work is
discussed in C.4.2.
B.2.3 Test devices
B.2.3.1 Deceleration test device
Front impact tests can be conducted using a deceleration device as long as the criteria in
Table 18 are achieved. The sled must weigh in excess of 380 kg (the TRL sled weighed
over 1000 kg to minimise any potential inertia effects of different CRSs) and remain
horizontal throughout the test.
Table 18: Front impact deceleration sled requirements
Stopping
distance
(mm)
Speed
(km/h)
Test
Restraint type
Forward facing
50
+0
Trolley with test
seat
/-2
650±50 */
Rearward facing
50
+0
/-2
650±50 */
B.2.3.2 Acceleration test device
Alternatively the front impact testing can be conducted using an acceleration device as
long as the following dynamic testing conditions are met:
•
The total velocity change (•V) of the trolley must be 52
•
The acceleration curve is within the hatched area shown in Figure 42
•
The curve must also stay above the segment defined by the coordinates (5g,
10ms) and (9g, 20ms), shown in Figure 42.
*/ During calibration, the stopping distance should be 650
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+0
/-2 km/h
± 30 mm
CPR821
•
The start of the impact (T0) is defined, according to ISO 17 373 for a level of
acceleration of 0.5g
•
The mass of the trolley, equipped with its seat, must be greater than 380 kg
However, if the tests were performed at a higher speed and/or the acceleration curve
has exceeded the upper level of the hatched area and the child restraint meets the
requirements, the test shall be considered satisfactory.
B.2.4 CRS installation
The installation of a CRS and test dummy in the new regulation is based on the
procedures in the current Reg.44. However some of this process is open to
interpretation, which can lead to inconsistency across Technical Services.
Many ISOFix CRSs have adjustable anchorages, allowing the CRS to be fitted tightly to
the vehicle seat cushion. Reg.44 specifies that ISOFix restraints should be installed using
a procedure that relies to an extent on the CRS to ratchet towards the seat bight.
Application of a small additional force is allowed, below a certain height. However there
are many CRS designs that require a lever to be held open while the force is applied to
the restraint, in order to activate the ratchet feature. This can therefore create
differences, in the way these CRSs are attached to the test bench, across different
Technical Services.
If the child restraint system uses a top tether Reg.44 specifies that the top tether should
be installed after the ISOFix attachments have been latched and tightened. The action of
tensioning the top tether can result in the front of the CRS lifting from the test seat
cushion, which can result in a set-up that is not recommended by the manufacturer and
this may lead to differences with installation.
In the case of a support leg with adjustable steps, the support leg length must be
adjusted such that the support leg is in contact with the test bench floor and adjusted to
its maximum and minimum position, compatible with the floor pan. Ensuring good footfloor contact can vary depending on the angle of the support leg. However, the angle of
support leg placement is not always defined by the manufacturer. Therefore an estimate
may have to be made, which can lead to a variation in set-up across Technical Services.
The proposal in the current new regulation for positioning the dummy is an improvement
compared to Reg.44, but needs completing with a setting-up procedure that is
measurable, where possible. For example when setting a dummy into a rearward facing
infant carrier, the dummy foot position can affect the results in rear impact. The foot
position and leg positioning are undefined.
For forward facing CRSs the new regulation recommends placing the dummy’s arms on
the legs, however the Q1 dummy arms aren’t long enough to reach the legs.
B.2.5 Assessment criteria
The front impact criteria to be assessed in the new regulation are:
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•
HIC15 (where there is hard contact – in bodyshells)
•
Cumulative 3ms resultant Head Acceleration
•
Upper Neck Tension Force Fz
•
Upper Neck Moment My
•
Thorax Acceleration Cumulative 3 ms
•
Thorax Chest Deflection Dx
•
Lower Lumbar Load Cell Force
•
Lap belt force (booster seats only)
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•
Horizontal and Vertical Head Excursion
The performance limits for these criteria proposed by the Informal Group are detailed in
Section B.5.3. Although it should be noted that for the purposes of this evaluation
project, extra data were acquired, namely lower neck forces and moments and pelvis
acceleration. The lower lumbar forces and moments, and lap belt forces do not yet have
proposed performance limits.
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B.3 Rear Impact
The rear impact test proposed in the new Regulation is based on the Reg.44 rear impact
test with some minor equipment and assessment changes.
B.3.1 Test Bench
The rear impact test in the new regulation uses the front impact bench rotated 180o
(Figure 43: Rear impact sled). The test procedure uses the test bench and cushions
described in Section B.1, the co-ordinate system defined in Section B.1.3 and the
anchorage positions defined in Section B.1.5.
Figure 43: Rear impact sled
B.3.2 Sled pulse
The current proposal in the new regulation is to use the Reg.44 rear impact pulse (Figure
44). A valid calibration run, which must meet the corridor and the defined input criteria
specified for test devices, must be conducted before each set of testing (Table 18). Table
18 shows the coordinates of the upper and lower corridors of the rear impact pulse.
Acceleration devices have different requirements to deceleration devices and these
differences are shown in B.3.3.
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Figure 44: Rear impact pulse
Table 19: Rear impact pulse coordinates
Time
(ms)
Deceleration
Deceleration
(g)
(g)
0
-
21
10
0
10
7
-
20
14
-
37
14
-
52
7
-
52
0
70
-
21
70
-
0
B.3.3 Test devices
Rear impact tests can be conducted using a deceleration device as long as the criteria in
Table 20 are achieved. The sled must weigh in excess of 380 kg (the TRL sled weighed
horizontal throughout the test.
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Table 20: Rear impact deceleration sled requirements
Test
Restraint type
Trolley with test
seat
Rearward facing
Stopping
distance
(mm)
Speed
(km/h)
30
+2
/-0
275±25 **/
Alternatively the rear impact testing can be conducted using an acceleration device as
long as the following dynamic testing conditions are met:
•
The total velocity change (•V) of the trolley must be 30
•
The acceleration curve is within the hatched area shown in Figure 44
•
The curve must also stay above the segment defined by the coordinates (5g,
5ms) and (10g, 10ms), shown as a red line in Figure 44.
•
The start of the impact (T0) is defined, according to ISO 17 373 for a level of
acceleration of 0.5g
•
The mass of the trolley, equipped with its seat, must be greater than 380 kg
+2
/-0 km/h
However, if after calibration, the tests are performed at a higher speed and/or the
acceleration curve has exceeded the upper level of the hatched area and the child
restraint meets the requirements, the test shall be considered satisfactory.
The installation issues for the rear impact test along the same lines as the examples
given in B.2.4 for front impact set-up.
The rear impact criteria to be assessed in the new regulation are:
The front impact criteria to be assessed in the new regulation are:
•
HIC15 (where there is hard contact – in bodyshells)
•
Cumulative 3ms resultant Head Acceleration
•
•
Upper Neck Moment My
•
Thorax Acceleration Cumulative 3 ms
•
Thorax Chest Deflection Dx
•
Horizontal and Vertical Head Excursion
Section B.5.3. Although it should be noted that for the purposes of this evaluation
project, extra data were acquired, namely lower neck forces and moments and pelvis
acceleration.
**/ During calibration, the stopping distance should be 275 ± 20 mm
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B.4 Side Impact
The side impact test procedure is not yet finally defined in the proposed regulation. The
proposal for future inclusion in the new Regulation is based on a test method devised by
DOREL France (CRS-10-03). The test is intended to be simplified and not representative
of a vehicle impact. The test speed is 26 km/h side impact with linear intrusion.
B.4.1 Test bench
The proposed side impact test procedure originally used the Reg.44 test bench and
cushions mounted 90o on the test rig (Figure 45). The child restraint was attached to
sliding ISOFix anchorages, which are able to move laterally away from the intruding door
during an impact. The coefficient of friction of these anchorages has yet to be defined.
Figure 45: Original side impact test rig (CRS-14-4)
The bench design was revised to use the widened NPACS bench dimensions and cushions
that have been proposed for the front and rear impact tests (see Figure 46 and
Figure 47). For the side impact tests, a small modification to the backrest cushion; a
50 mm cut-out has been made to allow the ISOFIX anchorages to slide without
interference. Currently the distance that the ISOFix anchorages can slide and the friction
coefficient, has yet to be defined in the draft Regulation. The DOREL sled design allowed
the anchorages to slide 195 mm, which was mimicked, to allow comparison, by the TRL
test sled. On both test sleds the ISOFix anchorages were fixed together, so that the
anchorages displaced an equal amount.
This means the test bench design and cushion properties are harmonised as far as is
possible for the three test configurations in the proposed new regulation. The 50mm cutout will need to be replaced in the cushion when testing CRS attached by only the seat
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belt to prevent the restraint interacting with the cushion gap, which would not exist in a
vehicle.
Figure 46: Side impact test rig
Measurements ±2mm
Angles ±0.5o
50
50
Figure 47: Test cushion dimensions
B.4.2 Door
The dimensions of the door panel are shown in Figure 48. The door is made from a rigid
material and mounted off-board the sled. The face of the door is covered by 35 mm of
rubber foam (Polychloropren CR4271), on top of which a 20 mm Styrodur C2500 sheet is
attached. The Styrodur sheet should be replaced after each side impact test.
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20 mm
Figure 48: Door specification
B.4.3 Test devices
Figure 49 shows the sled velocity corridor proposed for deceleration sleds in the new
regulation. It is recognised that this corridor is representative of the vehicle chassis
velocity of the struck vehicle in a side impact test and does not represent the velocity of
the intruding door in the struck vehicle. The implications of this are discussed further in
Section C.6.4.
A valid calibration run must be conducted before each set of testing, which must meet
the corridor and the defined stopping distance (300mm). The relative velocity between
the door panel and the test bench must not be affected by contact with the CRS. The
requirements for deceleration devices are listed in B.4.3. Table 21 shows the coordinates
of the upper and lower corridors of the side impact velocity corridor.
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Figure 49: Side impact velocity corridor
Table 21: Side impact velocity corridor coordinates
Time
(ms)
Velocity lower Velocity upper
corridor
corridor
(km/h)
(km/h)
0
15
25.20
23.40
27.00
18
-
25.56
65
-
70
0.00
-
80
-
-
2.16
0.00
In addition to meeting the velocity pulse above, for deceleration sleds the criteria in
Table 22 must achieved. The sled must weigh in excess of 380 kg (the TRL sled weighed
horizontal throughout the test. It should be noted that there is no tolerance on the
stopping distance and that for the purposes of calibration tests at TRL a stopping
distance of 295-300 mm was used.
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Table 22: Side impact deceleration sled requirements
Test
Restraint type
Speed
(km/h)
T0
Intrusion
(mm)
Stopping
distance
(mm)
Side Impact
All
26 +/-1
-50
300*
*No tolerance has been set, therefore for the calibration run, 295-300mm was accepted
At present no acceleration device specifications have been created for the side impact
test. The question whether it is even possible to recreate this test on an acceleration
device needs to be investigated.
B.4.4 Intrusion
The original, Dorel, proposal for the door intrusion is shown in Figure 50. This shows that
originally it was proposed that at T0 the door should have already travelled 50 mm over
the cushion (350 mm from the bench centre). The door should then be allowed to travel
up to 300 mm further, therefore achieving 350 mm intrusion from T0.
Figure 50: Original intrusion specifications
However as discussion in the GRSP Informal Group progressed, it was proposed that the
door should only intrude 250 mm. This was because evidence from whole vehicle crash
tests presented in the ISO TC22/SC12 document ISO/PDPAS 13396 (2009), showed that
250 mm was a more realistic intrusion depth for the severity of accident being
represented in the test.
Figure 51 shows the intrusion depth measured from cars representing different sizes and
different manufacturing dates in the UNECE side impact type approval test (R95) (ISO
TC22/SC12, 2009). The R95 test involves impacting the test vehicle with a Mobile
Deformable Barrier at 50 km/h. The lateral intrusion was measured close to the
dummy’s head. This shows the average intrusion depth of the corridor is 250mm. The
implications of this are discussed further in Section C.6.4.
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Figure 51: Intrusion depth measurements R95 tests (reproduced from
ISO/PDPAS 13396, 2009)
Figure 52 shows that at T0 the door is 50mm off board of the bench, and then can travel
300mm, resulting in 250mm intrusion. These conditions were used for the testing
conducted by TRL.
250mm
50mm
Figure 52: Intrusion specifications evaluated by TRL
As with front impact, the installation process for the CRS and the dummy has mainly
been taken from Reg.44. This needs clearer definition with tolerances on the
requirements. In addition to the set-up requirements mentioned in B.2.4 the proposed
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new regulation incorporates some additional requirements that are specific to the
installation of the dummy for side impact testing. The proposal requires the following
parameters to be controlled:
•
Alignment of dummy centre line with CRS centre line and CRS centre line with the
centreline of the bench
•
Pre impact stability of the dummy
•
Arm position relative to the torso
The CRS and dummy must be kept stable until t0 and this is to be checked by markers
on the dummy, CRS and sled. Any means used to stabilise the dummy before t0 must
not influence the dummy kinematics after t0. However this still does not clarify some of
the specific positioning aspects of the dummy, although the limb joints, neck and head of
the Q-series dummy are "fixed" and are not as variable as the P-series. However this
means that if it is necessary to change the position of the dummy, during installation, it
can be difficult. As previously mentioned, the arms of some of the dummies are not long
enough to rest on the legs when the upper arm is in line with the sternum.
The side impact criteria to be assessed in the new regulation are yet to be defined. The
proposal is currently for the main injury assessment criterion to be based on head
containment. The proposal is specified such that during the loading phase of the lateral
impact (up to [80] ms) the side protection must always be positioned at the level of the
centre of gravity of the dummy’s head, perpendicular to the direction of the door
intrusion. The containment is to be assessed by a video analysis. One proposal is for
assessment by the use of front-on and overhead cameras. This includes judgement of
head containment, based on:
•
•
•
No head contact with the door panel.
Head must not exceed a line on the top of the door (top camera view).
Head must not exceed the side wing of the CRS or (options to be selected during
evaluation phase) marker on dummies head (side camera view) must not show a
complete black circle (from a TUB sticker design). A figure is to be developed to
describe the sticker and these head containment criteria.
This TUB procedure for assessing the head containment is not yet clearly defined.
Therefore the method currently published for NPACS for assessing head containment
from the overhead and off-board side video recordings of the tests was used for this
project. For the larger dummies (Q3, Q6) a third camera mounted behind the door was
also used to assess dummy head containment. 20 mm targets were placed on the side of
the dummies’ head, at the centre of gravity, to aid in this assessment.
During the dynamic tests, no part of the child restraint system actually helping to keep
the child in position shall break (this is, in practise, subjective), and no buckles or
locking system or displacement system shall release.
It is permissible for parts of the seat to deform provided that, in doing so, it does not
directly affect the ability of the seat to protect the occupant (this will also be a subjective
assessment).
Additional Injury assessment criteria
The assessment is to take into account energy absorbtion. HIC36, or resultant head
acceleration (3ms) is to be considered. The criteria for front and rear impact are based
on HIC15 values. So there should be consistency here and HIC15 should be used. These
values are to be established after an evaluation program. It was therefore decided that
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for the purposes of this evaluation the same dummy measurements assessed in front
impact would be analysed in side impact. The exception is the dummy neck moment,
where Mx positive and negative would be analysed. The full list of assessed dummy
criteria for this project was therefore:
•
HIC15
•
Head Acceleration Cumulative 3ms
•
•
Upper Neck Moment Mx
•
Lower Neck Tension Force Fz
•
Lower Neck Moment Mx
•
Thorax Acceleration Cumulative 3ms
•
Thorax Chest Deflection Dy
•
Pelvis Acceleration Cumulative 3ms
•
Lower Lumbar Load Cell Force
Section B.5.3. Although it should be noted that lower neck forces and moments, pelvis
acceleration, and lower lumbar forces and moments do not yet have proposed
performance limits.
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B.5 Dummies and performance requirements
B.5.1 Dummy design
FTSS (CRS-03-14) presented the Q-series dummies, the history of their development,
and the instrumentation available. The list of instrumentation available for the Qdummies is shown in Figure 53 and Table 23. The mass of the dummies is shown in
Figure 54.
Figure 53: Q-series instrumentation
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Table 23: Q-series instrumentation
Location
Description
Linear accelerations
3-axis
accelerometer
Ax, Ay, Az
Angular
accelerations
3-axis
accelerometer
Wx, Wy,
Wz
Forces
6-axis upper neck
load cell
Fx, Fy, Fz
Head
Upper neck
Moments
Lower neck
Forces
6-axis lower neck
load cell
Moments
Thoracic spine
Mx, My, Mz
Fx, Fy, Fz
Mx, My, Mz
3-axis
accelerometer
Ax, Ay, Az
Deflections
IR-Tracc or
stringpot
Dx or Dy
3-axis
accelerometer
Ax and/or
Ay
6-axis lumbar load
cell
Fx, Fy, Fz
Thorax 'ribcage'
Lower lumbar
spine
Pelvis
Forces
Moments
3-axis
accelerometer
Mx, My, Mz
Ax, Ay, Az
Figure 54: Q-series dummies
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influence another. For example, the motion of the head is influenced by the stiffness of
the neck and the torso. TRL compared the Q3 dummy measurements in quasi-static
tests with targets proposed in the literature (Visvikis et al., 2007). This revealed that the
Q3 did not meet all of its performance targets. The greatest deviations were found in the
chest and the shoulder. The chest was too stiff in both the front and side impact
directions, while the shoulder was too stiff to meet the side impact target. This needs to
be taken into consideration when using criteria limits that have been set by using scaled
adult injury information. If these dummies prove to be the best current ATDs available, a
more pragmatic approach to assessment criteria and the associated limits may need to
be taken, based on the performance of CRSs with a known history in the field.
B.5.2 EEVC Q-dummy injury criteria and performance criteria
EEVC Working Groups 12 and 18 produced a report detailing the development of the Qseries dummies and associated criteria for use in frontal impact (Wismans et al., 2008).
FTSS presented the results of this report and their subsequent, further analysis of the
data, to the GRSP Informal Group. The original report describes the design and
evaluation of the Q-series child dummies. These dummies were developed to replace the
P-dummies in the UNECE Regulation and the report provides background on the research
and development efforts that resulted in the new Q dummy and its injury assessment
reference values. EEVC WG18 reviewed European accident statistics. The study
discussed the body areas that needed to be protected for different ages of child, and
hence where this new generation of child dummies should have injury assessment
capabilities.
The EEVC report goes on to describe the research from the CREST and CHILD projects,
based on accident reconstructions, that resulted in dummy age/size specific injury
assessment reference values (IARVs). The use of the term IARV in the EEVC report
differs from that used by ISO: in the EEVC report this simply means a threshold value for
a given risk of injury, which could be 50% risk or any other defined value, whereas ISO
usually use IARV to mean ‘a human response level below which a specified significant
injury is considered unlikely to occur’, i.e. a lower bound for injury thresholds (Mertz,
1993).
The IARVs were developed by EEVC WG12/18 using data from 40 validated
reconstructions of real world accidents, which were conducted during the CREST and
CHILD EC projects. The reconstructions were performed using the Q0, Q1, Q3 and Q6
dummies, as well as the P1.5 dummy, in frontal impacts. The injuries observed in the
accident cases were compared with the measurements from the dummies in the
reconstructions. All the data were scaled to the Q3 dummy size/age, injury risk functions
were calculated, and the resulting performance requirements scaled to the other
sizes/ages of dummy. The work resulted in two sets of IARVs, one based on 20% risk of
AIS3+ injury (Table 24) and one based on 50% risk of AIS3+ injury (Table 25).
WG12/18 also scaled the UNECE R94 front impact, adult 50th percentile performance
requirements to the Q-series dummies (Table 26). Note that the HIC derived from the
accident reconstruction data is HIC15 and that from R94 is HIC36, so the two are not
directly comparable.
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Table 24: Q dummy performance criteria for 20% risk of AIS3+ injury
(calculated using logistic regression)
Criteria
Q0
Q1
Q1.5
Q3
Q6
Head injury criterion
HIC15
523
491
578
780
1083
Head acceleration
(3 ms exceedence)
Ah (g)
85
72
76
81
89
Upper neck tension
force1
Fz (N)
498
1095
1244
1555
2101
Upper neck flexion
moment1
My (Nm)
17
53
61
79
118
Chest compression
Dx (mm)
N/A
40
38
36
33
1
Upper neck tension force (Fz) and flexion moment (My) values come from literature scaling and are not
specifically associated with the logistic regression results
Table 25: Q dummy performance criteria for 50% risk of AIS3+ injury
(calculated using logistic regression)
Criteria
Q0
Q1
Q1.5
Q3
Q6
HIC15
671
629
741
1000
1389
Head acceleration
(3 ms exceedence)
Ah (g)
104
88
93
99
109
Upper neck tension
force1
Fz (N)
546
1201
1364
1705
2304
Upper neck flexion
moment1
My (Nm)
20
64
74
96
143
Chest compression
Dx (mm)
N/A
59
56
53
49
1
Upper neck tension force (Fz) and flexion moment (My) values come from literature scaling and are not
specifically associated with the logistic regression results
2
Chest compressions larger than 55 mm are considered unrealistic from human point of view and physically
impossible to measure with the Q-dummies
Table 26: Q dummy performance criteria scaled from UNECE R94 adult
performance criteria
Criteria
Q0
Q1
Q1.5
Q3
Q6
HIC36
477
447
526
710
986
Head acceleration
(3 ms exceedence)
Ah (g)
79
67
70
75
82
Upper neck tension
force
Fz (N)
433
951
1080
1350
1824
Upper neck flexion
moment
My (Nm)
13
42
48
63
94
Chest compression
Dx (mm)
N/A
52
49
47
42
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EEVC WG12/18 then undertook a study to quantify the effect of the introduction of the
Q-dummies and the above potential new criteria in UNECE Regulation 44 through an
assessment program with more than 320 Reg.44 front impact tests (including P- and Qseries tests). This involved assessing the proportion of each CRS group that would fail
each of the potential performance criteria, and these results were summarised by FTSS
in a document submitted to the UNECE GRSP Informal Group on child restraints (CRS03-14). The Reg.44 tests that were conducted with the Q-series dummies on 30 different
CRS models as shown below:
•
34 tests on 6 Group 0+ child restraints
•
62 tests on 12 Group I child restraints
•
25 tests on 6 Group I/II/III child restraints tested as Group I
•
37 tests on 9 Group I/II/III child restraints tested as Group II
When the calculated injury values were applied to the test results the results showed
that the majority of Group 0+ restraints met the proposed performance criteria, but the
majority of the Group I and Group II child restraints failed the criteria (Table 27 and
Table 28).
Table 27: AIS3+ 20%
Group
Passed
Failed
(%)
Group 0+
5 (83%)
1
Group I
2 (17%)
10
Group I (I/II/III)
0 (0%)
6
Group II
(I/II/III)
0 (0%)
9
Table 28: AIS3+ 50%
Group
Passed
Failed
(%)
Group 0+
5 (83%)
1
Group I
4 (33%)
12
Group I (I/II/III)
2 (33%)
4
Group II
(I/II/III)
3 (33%)
6
On the basis of this feasibility evaluation, the EEVC recommended the use of the set of
performance criteria based on the 50% injury risk level (Table 25), but noted that these
limits would be likely to be very challenging for Group I and Group II (and probably
Group III) CRSs.
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B.5.3 GRSP informal group discussion on performance criteria
Subsequent to the EEVC report, the GRSP Informal Group have given further
consideration to the need for the different measurements that are possible with the Qseries dummies, and to the performance criteria that should be used in assessing
whether a CRS has been designed in such a way as to mitigate injury to a child. The
current draft of the new regulation includes the proposed performance criteria shown in
Table 29. It should be noted that the upper neck tension force and flexion moment are in
square brackets, indicating that these performance criteria are still under discussion.
Table 29: Proposed dummy performance criteria
Risk
AIS3+
Criterion
Abbrev.
Unit
Q0
Q1
Q1.5
Q3
Q6
Q10
Head Injury
Criterion*
HIC15
-
523671
491629
578741
7801000
1083
1389
?
20%50%
Head Resultant
Acceleration 3ms
A head
3ms
g
85
72
76
81
89
?
20%
Upper Neck
Tension Force
Fz
N
[546
1201
1364
1705
2304
?
50%]
Upper Neck
Flexion Moment
My
Nm
[17
53
61
79
118
?
20%]
Thorax Chest
Compression
D Chest
mm
N/A
40
38
36
33
?
20%
Chest
Acceleration 3ms
A chest
3ms
g
55
55
55
55
55
?
Reg.44
values
*Only assessed if hard contact occurs during in-vehicle testing and in side impact (side impact limits not
decided)
Head acceleration 3 ms exceedence: Fewer than 10% of the CRSs tested in the EEVC
programme failed these criteria, which suggests that this may be a reasonable level for
future regulation. However it is well known that infants are at greater risk of head injury
than older children, so it doesn’t seem reasonable to have a higher limit for the Q0.
Upper neck tension force Fz and flexion moment My: CRS-12-4 notes that the proposed
upper neck force criteria would fail most existing CRS, even though a high 50% risk level
is recommended. By contrast, all CRSs would pass the My requirement. CRS-12-4
appears to recommend that the performance criterion for both parameters should be set
to the 50% risk level. However, the current proposal retains the 20% level for My, and it
is important that this is maintained. The accident review showed that there are very few
neck injuries in the field with CRS that pass at the 20% level, and introducing a criterion
that allowed performance to degrade from Reg.44 levels may lead to neck injuries
becoming more common in the future. Furthermore, setting the Fz criterion to a level
that fails 50% of current CRS seems unreasonable given the low rate of neck injuries in
the field.
Chest compression: The chest compression values would fail 20% of the CRS tested in
the EEVC work, which does not seem to be unreasonable for a new regulation. However,
there needs to be some evaluation of how this measurement and the associated injury
risk function work, because the threshold for 50% risk of injury (>55 mm) were greater
than that allowed for adult dummies and greater than can be measured with the
Q-series dummies. In addition to this, it doesn’t seem reasonable that a 1 year old can
sustain more compression than a 6 year old. Consideration should also be given to how
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reliable the chest compression criterion will be for systems where the harness does not
load the centre of the chest.
The measured head excursions of the dummy are also assessed and must be within the
following limits:
The limits for forward facing child restraints are (Figure 55):
•
Horizontal - 550 mm (do not pass the A-B plane)
•
Vertical - 800 mm (do not pass the A-D plane)
•
Do not pass the D-Cr plane
Figure 55: Forward facing child restraints – head excursion
This forward facing limit allows 50mm more than that which is currently allowed for
ISOFix CRSs in Reg.44, which bearing in mind that the head is the most important body
region to protect for children in forward facing CRSs, seems to be a step backward for
child safety.
The limits for rearward facing child restraints are (Figure 56):
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•
Horizontal - 700 mm (do not pass F-G plane)
•
Vertical - 800 mm (do not pass D-F plane)
•
Do not pass the D-E plane
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D
F
800
E
G
Cr
G
Dimensions in mm
700
Figure 56: Rearward facing child restraints – head excursion
B.5.4 Bending moment – lateral bending
No lateral bending moment limits have been proposed for use with the new regulation in
side impact testing. A side airbag OOP injury technical working group was set up in the
US to develop a common understanding of the risks associated with side airbag
deployments and ways to minimise those risks (Lund, 2003). This working group was
sponsored by the Alliance of Automobile Manufacturers, Association of International
Automobile Manufacturers, Automotive Occupant Restraints Council, and Insurance
Institute for Highway Safety. This group recommended that:
“The lateral bending moment values were set midway between the
extension and flexion values because the amount of muscle and connective
tissue that resists lateral bending is greater than the amount that resists
extension bending, but not greater that the amount that resists flexion, the
neck’s strongest bending mode. (Lund, 2003)”
Adoption of this strategy to the forward facing, side impact, CRS results would lead to
the peak values measured for lateral bending passing the criterion. This may prove a
useful criterion for monitoring in the future.
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Appendix C
Practical assessment of proposed
procedures
C.1 Introduction
The proposals made by the GRSP informal working group for front, side and rear
dynamic test methods have been presented, with initial comments, in Appendix B. This
section of the programme was designed to evaluate the proposals, with a view to
providing recommendations for the way forward.
The practical assessment of the procedures included child restraint selection C.2. Using
these CRSs, the front impact test procedures were assessed, with the addition of an
alternative pulse. This assessment evaluated the relevance and limits of the dummy
criteria proposed by the informal group. The performance specification for test bench
foam was also considered. The rear impact tests were evaluated to gain an
understanding of the relative effect of the geometry and cushion properties of the new
proposed test bench on the performance of CRSs compared to those of the test bench
specified in UNECE Reg.44. The implications of using the Q-series ATD criteria and limits,
proposed by the informal group for dynamic assessment of CRSs in rear impact, were
also assessed. Side impact tests were carried out to identify how the test procedure
loads restraint systems and how this relates to accidents in the real world. The
procedure was assessed for repeatability and reproducibility and the dummy criteria and
limits for side impact were also evaluated.
C.2 Child restraint selection
The CRSs for the practical assessment programme were short-listed using a combination
of market research information and knowledge about CRS performance. The seats were
selected based on reported performance (good and poor) and volume sales.
It was important to assess the proposed procedures by using CRSs that have had a high
volume of sales and hence, have a wide history of use in the European vehicle fleet. CRS
models generally have, at the very least, five years in the market before they are
discontinued as a product. By including these products it provides a certain level of
confidence that if the products are likely to cause injury to children in the way they
provide restraint under crash conditions, the accident studies will reflect this.
If the practical assessments show high dummy readings compared to the limits set for
the dummy criteria when testing with these products, in a body area that is not
considered a priority for protection, then it suggests that there is an issue with the
specification rather than an issue for child protection and the CRS. For example, the limit
proposed for the criteria may not be set at the correct level, or there may be an issue
with the dummy design for the body region in question, or there may be an issue with
the testing conditions of the assessment procedure.
The reported, dynamic performance of child restraint systems (taken from various
consumer testing schemes) was also considered during the selection process, to provide
a reasonably representative range of CRS performance across the limited number of
products in available within the scope of the programme.
The first phase of the work for the new Regulation is focussed on integral ISOFix
restraint systems, however the new Regulation will, in the longer term, need to work for
all child restraint types and these include adult belt attached systems and adult belt
restrained occupants. Belt attached systems may have an impact on test set-up that is
not observed for ISOFix systems and it is for this reason that we have included nonintegral systems and an adult belt attached restraint system in our selection.
The short-list for the selection of CRSs are detailed in Table 30 to Table 32.
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Table 30: Rearward facing integral CRSs (Group 0+) short-list
ISOFix
In order of
lowest
reported
performance
In order of
highest
reported
performance
In order of
highest
volume
sales
1
IWH (Stella), Babymax
2
Emmajunga, First Class
1
2
1
2
3
Britax, Babysafe
Recaro, Young
Maxi-Cosi,
Profi
Cabriofix
Maxi-Cosi, Cabriofix
M&P, Primo Viaggo
Britax, Babysafe
1
Belt
Petite Star
Aluminium Handle
1
Graco, Logico S
I'coo C-Care
Jane Strata
2
Fisher Price, Safe voyage
3
1
2
3
4
Britax, Babysafe Beltbase
Bebe Confort, Creatis
Meggy, Babystart
Silver Cross, Ventura
Table 31: Forward facing integral CRSs (Group I) short list
In order of
lowest
reported
performance
In order of
highest
reported
performance
In order of
highest
volume
sales
1
2
ISOFix
Nania, Cosmo
Recaro, Young Expert
1
Maxi-Cosi, Priorifix
2
1
2
3
4
Britax, Duo
1
2
3
4
1
Belt
M&P, Protec
Chicco, Key 1
Bebe Confort, Axis
Britax, Duo
Maxi-Cosi, Tobi
Britax, King
Britax, Safefix
Bebe Confort, Iseos
Britax, Duo
Britax, Safefix
1
2
3
Maxi-Cosi, Priori XP
Bebe Confort, Axiss
Chicco, Key 1
Table 32: Forward facing non-integral CRSs (Group II/III) short list
In order of
lowest
reported
performance
In order of
highest
reported
performance
In order of
highest
volume
sales
1
ISOFix
Jane, Monte Carlo
1
Belt
Alpine, Daisy
2
Jane, Indy Plus
3
Sunshine Kids, Monterey
1
Cybex, Solution X-fix
1
Cybex, Solution X
2
Britax, Kidfix
2
Kiddy, Discovery Pro
1
Britax, Kidfix
1
2
3
4
Graco, Junior Maxi
Graco, Logico L
Nania, Befix
Nania, Dreamfix
The product selection, based on performance was made first. The volume sales
information was then used to ensure the selection included products that had a history in
the field. When selecting products based on sales, if the product had already been
selected on a performance basis, the next highest volume seller was selected. Table 33
shows the CRSs selected for the practical assessment of the procedures.
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Table 33: CRSs selected to assess protocols
Short name
Infant 1 (Low Rating)
Infant 2 (High Rating)
Infant 3 (High Sales 1)
Safety 1 (Low Rating)
Safety 2 (High Rating)
Safety 3 (High Sales 1)
Safety 4 (High Sales 2)
Booster 1 (Low Rating)
Booster 2 (High Rating)
Booster 3 (High Sales 1)
Booster 4 (High Sales 2)
Product
IWF (Stella), Babymax
Britax, Babysafe
M&P, Primo Viaggo
Nania, Cosmo
Bebe Confort, Iseos
Britax, Duo
Jane Monte, Carlo
Cybex, Solution X-fix
Britax, Kidfix
Sunshine Kids, Monterey
Attachment method
ISOFix Base with Support Leg
Belt
ISOFix & Top Tether
ISOFix & Support Leg
ISOFix & Top Tether
ISOFix & Top Tether
Belt & ISOFix
Belt & ISOFix
Belt & ISOFix
Belt & ISOFix
C.3 Test Bench
The test bench used in the practical assessment was that proposed by the Informal
Group (based on the NPACS research) and specified in Section B.1. The type of foam
that is required for the test bench is currently specified as a particular parts number,
available from FTSS (T75500), but there is no performance specification for the foam so
the performance of different batches of foam may differ. It is not known how much this
may affect the reproducibility of the test procedure, but it is certainly not good practice
to leave this aspect of the test bench performance uncontrolled. Furthermore, it would
be useful to have a performance specification to allow the possibility of sourcing the
foam from a wider number of suppliers. The performance specification for test bench
foam was considered within this project. This section outlines the extent of the TRL
assessment, which is expected to contribute to a wider set of results within the GRSP
Informal Group.
The UNECE Reg.44 test bench calibration rig was used for these tests (section 8.3 of
Reg.44)
•
•
Calibration set-up as defined in section 8.3 of Reg.44
o
2.75 kg ball impactor (see annex 17)
o
Drop height 500 mm
o
Three impact locations as defined in 8.3.2 of Reg.44
o
Bench laid down horizontally at 0°
Two different configurations of the bench foam
o
Foam only, without cloth
o
Cloth installed according to Reg.44 (glued to the back plate)
Figure 57 shows the results of the tests with the uncovered foam and Figure 58 shows
the results of tests with the covered foam. For each set of results, the mean of the six
impact responses is shown in red. A target corridor is also shown in black. This was
calculated by finding the maximum value of the standard deviation throughout the
impact event (max SD), and plotting the mean ± max SD. It can be seen that both
graphs have spikes in some of the impact responses: these are thought to be due to
loose electrical connections, not due to any important characteristic of the foam or
impactor, and have been removed from the mean and maximum standard deviation for
the purpose of defining this target performance corridor.
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Ignoring the spikes, it can be seen that two out of the six uncovered foam response
curves (Figure 57) lie fractionally outside the target response corridor. However, it
appears that all the curves may lie within the corridor if more aggressive filtering was
used. These data were filtered using CFC 1000, although it is recommended that the
data are filtered with CFC 60.
30
Set 1 Foam - Mid
28
Set 1 Foam - Left
26
Set 1 Foam - Right
24
Set 2 Foam - Left
22
Set 2 Foam - Right
Set 2 Foam - Mid
Set 1-2 Foam: Mean
Deceleration (g)
20
Set 1-2 Foam: Mean + Max SD
Set 1-2 Foam: Mean - Max SD
18
16
14
12
10
8
6
4
2
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Time (s)
Figure 57: Seat foam impact responses for two sets of uncovered foam
It can also be seen that two out of the six covered foam impact responses lie outside the
target response corridor, and that these are unlikely to be affected by the filtering
regime used. However, the graphs show that they are likely to be affected by the tension
of the covering fabric. Any drop test procedure, defined to assess and certify the test
cushion characteristics, will need to specify two corridors, one for the uncovered foam
and one for the covered foam.
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Deceleration (g)
30
Set 1 Covered - Mid
28
Set 1 Covered - Left
26
Set 1 Covered - Right
24
Set 2 Covered - Mid
22
Set 2 Covered - Left
20
Set 2 Covered - Right
18
Set 1-2 Covered: Mean
Set 1-2 Covered: Mean + Max SD
16
Set 1-2 Covered: Mean - Max SD
14
12
10
8
6
4
2
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Time (s)
Figure 58: Seat foam impact responses for two sets of covered foam
C.4 Assessment of front impact proposals
The front impact test programme was designed to assess the front impact procedure
proposed by the GRSP Informal Group (Figure 62). These tests allowed assessment of
the relevance and limits of the dummy criteria proposed by the Informal Group. In
addition to this, a small comparison was made with a more severe pulse.
Figure 59: Front impact test sled
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The test speed proposed by the Informal Group is specified as 50km/hr +0/-2. Figure 60
shows the deceleration envelope proposed by the Group. This are also the conditions
currently used for type approval of CRSs in UNECE Reg.44. The test conditions for the
assessment are also shown below. The black acceleration traces represent the mean of
the test pulses and one standard deviation away from the mean. These are shown to
demonstrate that the test conditions were repeatable.
Figure 60: Proposed Deceleration Pulse Envelope, with deceleration pulses from
the experimental front impact testing.
C.4.1 Criteria Evaluation
C.4.1.1 Rearward facing integral restraints
The review of accident studies has shown that, for children injured in front impacts, the
head is the priority body region to protect. The majority of head injuries are caused by
contact with parts of the vehicle interior or other external objects. Chest and abdomen
injuries become more significant with increasing age of the occupant, along with pelvis
injuries. These were found to be predominately caused by the vehicle seat belt.
The test matrix for the practical assessment of the effects of the proposed front impact
procedure on rearward facing integral CRSs is shown in Table 34. The assessment used
three models of CRS with three dummies. The CRS models represent seats that received
low or high ratings in various consumer tests and seats that had high volume sales.
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Table 34: Front Impact assessment matrix – rearward facing integral CRSs
Child Restraint System
Group 0+ low rating
Babymax
Group 0+ high rating
Babysafe
Group 0+ high volume
Cabriofix
ATD
Tests
Q0
1
Q1
1
Q1.5
1
Q0
1
Q1
1
Q1.5
1
Q0
1
Q1
1
Q1.5
1
The results of the assessment with the rearward facing integral CRSs are shown in
Table 36. The CRSs pass all of the criteria proposed for the new regulation. The review
of accident studies indicated that head protection is a high priority for children travelling
in rear facing CRSs. The injury mechanism associated with these CRSs is head contact
with the vehicle dashboard or the vehicle interior, so head excursion is an important
factor. The range of horizontal head excursions were well inside the thresholds proposed
for the dummies.
displacement of the manikin's head. The uncertainty has to be within ± 25 mm. Reg.44
references examples of international standards of such procedures (EA-4/02 of the
European Accreditation Organization or ISO 5725:1994 or the General Uncertainty
Measurement (GUM) method). However, there is no requirement beyond this to control
how the visual analysis is carried out and this can lead to large differences between how
the laboratories interpret the application of U of M. The confidence intervals should be
specified and the method of applying these confidence intervals to the U of M needs to
be clearly defined.
Where possible, the head excursions were measured using the side view of the test. It is
not always possible, however, to see the top of the dummy’s head from the side, so in
some cases the top camera view was used. There are limitations with measuring the
excursions from the top view, as the dummy is constantly changing to a different
measurement plane during the test and the visual measurement, alone, is incorrect.
Therefore, a correction factor has been applied to the visual measurement. The
correction factor is calculated by using results from the tests where the difference
between the measurement views is known, i.e. where the dummy’s head can be seen
from both views. This is also an issue for type approval and the assessment method
should be defined more clearly. Although there is a pass fail plane, which can be
physically represented, in the assessment for type approval, the actual measured
excursions must be known in order to carry out Product Qualification testing (section 9 of
the proposed regulation) and for Conformity of Production testing (Annexe 13 of the
proposed Regulation).
The accident review suggests, head excursion is an issue for child protection, therefore
the performance thresholds for the testing may need to be changed, to encourage less
forward movement of these products in the field. The range for the CRSs with the Q0
was 49-56 % of the threshold; the Q1 was 53-69 % of the threshold and the Q1.5 was
in the range of 65-69% of the threshold, so there is scope for reducing the threshold for
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horizontal head excursion. The limit currently proposed is 700mm and the maximum
forward excursion across these tests was less than 500mm.
These results did not include any testing with large rear facing CRSs and one could argue
that a larger CRS with a larger dummy would need more space. However, the space
allowed for excursion should be based on the space available in the vehicle, which is
variable, and not based on dummy size. A limit of 500mm is used in UNECE Reg.44 for
universal forward facing ISOFix CRSs. This was justified, at the time of drafting, by some
UK accident reports of children (in forward facing CRSs), who had received head injuries
in accidents through contact with the seat in front, where the space for forward
excursion in the vehicle was judged to be less than 550mm from the “Cr” line. The value
for head excursion should be reviewed and based on the excursion space available to
children in modern vehicles, taking into account realistic vehicle front seat positions. One
may counter argue that by reducing the head excursion, the head accelerations would
increase and this indeed likely to happen, however the head accelerations measured in
this assessment were well below the threshold for injury, so there is the potential to
achieve a better balance between these two criteria.
The values for the linear head acceleration thresholds have been taken directly from the
work of the EEVC Working Groups 12 & 18 (Wismans et al., 2008). In particular, the Q3
threshold was derived from the accident reconstructions undertaken by those groups.
The value proposed for use as a performance criterion relates to the 20% risk of
sustaining an AIS 3+ head injury. This value was then scaled to the other dummy sizes
using the relationship shown below.
Where:
•• is the ratio of head acceleration (at the centre of gravity of the head),
••t is the ratio of head failure stresses (approximated to the failure stress
of the calcaneal tendon), and
•x is the ratio of head lengths
The values of these ratios for the different Q-dummies are shown in (cross ref to table
below). They are also graphically illustrated in (cross ref to figure below).
Table 35: Scaling ratios used in the development of the head acceleration
performance thresholds
Scaling
parameter
Q0
Q1
Q1.5
Q3
Q6
Adult
••t
0.63
0.7
0.75
0.85
0.96
1
•x
0.63
0.84
0.86
0.91
0.93
1
••
1.00
0.84
0.87
0.94
1.03
1
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Figure 61: Scaling ratios used in the development of the head acceleration
performance thresholds
The composition of the scaling formula and the progression of the ratios for failure stress
and head length seem sensible. In principle, the head acceleration expected to cause
injury would increase with age as, in general, human tissue becomes more resilient to
stress. Also experimental observations using animal models have indicated that certain
head injuries require higher levels of acceleration to inflict in subjects with smaller
heads. However, the particular values used in the approximation to Q-dummies might
not be ideal. This is shown by the effect of their combination for the Q0. Here the
general reduction in head acceleration ratio, towards the smaller dummies, suddenly
reverses and leaps to around one. Based on the values being used in the formula, this
effect is understandable.
However, it may not be a realistic representation of injury risk for children under the age
of one. Therefore it is suggested that the head acceleration threshold criterion for the
different Q-dummy ages needs to be reviewed. It may be that a different scaling
approximation would provide a more progressive function; one which may be more in
line with expectations surrounding injury tolerance for very young children. It should be
noted that without experimental data which can confirm the tolerance of children, the
discussions surrounding their tolerance can only be based on the engineering judgement
of experts in the field. Some validation of this opinion remains a fundamental
requirement in the application of child dummy measurements such as head acceleration.
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Table 36: Front impact results table – rearward facing integral CRSs
Group 0+ Child
Restraint Systems
Low rating
Babymax
High rating
Babysafe
High volume sales
Cabriofix
Low rating
Babymax
High rating
Babysafe
High volume sales
Cabriofix
Low rating
Babymax
High rating
Babysafe
High volume sales
Cabriofix
TRL
ATD
Head Head
exc
exc HIC15
H
V
Head
res ac
3ms
g
Upper
Neck
Fz
N
Upper
Neck
My
Nm
Lower
Neck
Fz
N
Lower
Chest
Chest
Neck compression res acc
My
3ms
Nm
mm
g
mm
mm
Limits
700
800
523671
85
546
17
N/A
N/A
N/A
55
Q0
395
512
127
54
165
0.8
N/A
N/A
N/A
38
Q0
340
428
136
42
173
0.7
N/A
N/A
N/A
41
Q0
367
524
117
43
99
0.8
N/A
N/A
N/A
39
Limits
700
800
491629
72
1201
53
N/A
N/A
40
55
Q1
485
658
216
49
650
9
N/A
N/A
5
37
Q1
374
616
232
50
390
7
N/A
N/A
3
35
Q1
432
672
222
52
189
7
N/A
N/A
3
39
700
800
578741
76
1364
61
N/A
N/A
38
55
Q1.5
483
579
158
42
728
11
N/A
N/A
4
41
Q1.5
468
646
215
50
426
6
N/A
N/A
2
31
Q1.5
458
667
216
49
350
6
N/A
N/A
2
36
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C.4.1.2 Forward facing integral restraints
procedure on forward facing integral CRSs is shown in Table 37. The assessment used
three models of CRS with two dummies. The CRS models, again, represent seats that
received low or high ratings in various consumer tests and seats that had high volume
sales.
Table 37: Front impact assessment matrix - forward facing integral CRSs
Group I Child Restraint
Systems
ATD
Tests
Low rating
Cosmo
Q1
1
Q3
1
High rating
Priorifix
Q1
1
Q3
1
High volume
Iseos
Q1
1
Q3
1
The results of the assessment with the forward facing integral CRSs are shown in
Table 38. The results in red show where the measured values have exceeded the
thresholds for the criteria.
The review of accident studies indicated that head protection is the highest priority for
children travelling in forward facing integral CRSs, followed by chest protection. The
injury mechanism associated with these CRSs is head contact with parts of the vehicle
interior, so head excursion is the most important criteria. However in optimising a CRS
to achieve low head excursions, this can result in high head and chest accelerations, so it
is important to have a balance of performance across all three criteria.
The horizontal head excursions for the smallest dummy (Q1) were 63%-69% of the limit
and the largest dummy (Q3) excursions were 81%-88% of the limit. All head excursions
were below 500mm the limit currently set for ISOFix integral restraints in Reg.44.
The CRS selected as “highly rated” slightly exceeded the threshold for head acceleration
(by 1%), with the Q1 dummy. The product performance ranged from 84%-101% of the
limit for this criterion with the Q1 dummy.
The CRS selected for high sales slightly exceeded the threshold for vertical head
excursion (by 1%) with the Q3 dummy. The low rated restraint also came close to
exceeding the limit excursion (99% of the limit). The product performance ranged from
97%-101% of the limit for this criterion with the Q3 dummy. This shows that the
800mm head vertical excursion limit is about right for this type of restraint.
accidents. However, in all the tests with the Q1 or Q3 in integral CRSs, the dummy
produced upper neck tensile forces which exceed the proposed threshold (they were on
average 149% of the threshold). This limit relates to an expected 50 % risk of AIS • 3
neck injury (as scaled for the child size; EEVC, 2008). Therefore it seems to be the case
that the proposed equipment, measurement tools or procedures do not lead to an
accurate assessment of injury risk for this body region.
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Table 38: Front impact results table – forward facing integral CRSs
Group I Child
Restraint Systems
Head Head
exc
exc
H
V
HIC15
Head
res ac
3ms
g
Upper
Neck
Fz
N
Upper
Neck
My
Nm
Lower
Neck
Fz
N
Lower
Chest
Chest
Neck
res acc
compression
My
3ms
Nm
mm
g
mm
mm
Limits
550
800
491629
72
1201
53
N/A
N/A
40
55
Low rating
Cosmo
Q1
344
682
366
60
1636
18
N/A
N/A
20
43
High rating
Priorifix
Q1
348
730
327
73
1391
15
N/A
N/A
17
34
High volume sales
Iseos
Q1
377
701
479
64
1750
22
N/A
N/A
19
40
550
800
7801000
76
1364
61
N/A
N/A
38
55
Q3
462
799
414
63
2540
10
1106
123
28
35
Q3
447
772
283
55
1713
9
1133
91
24
33
Q3
483
807
449
63
2485
21
1249
110
5†
34
Low rating
Cosmo
High rating
Priorifix
High volume sales
Iseos
†
ATD
Error in data channel
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C.4.1.3 Forward facing non-integral restraints
procedure on forward facing non-integral CRSs is shown in Table 39. The assessment
used three models of CRS with two dummies. The CRS models represent seats that
received low or high ratings in various consumer tests and seats that had high volume
sales.
Table 39: Front impact assessment matrix - forward facing non-integral CRSs
Group II Restraint
Systems
ATD
Tests
Low rating
Monte Carlo
Q3
1
Q6
1
High rating
Solution X-fix
Q3
1
Q6
1
High volume
Kidfix
Q3
1
Q6
1
The results of the assessment of the procedures using non-integral CRSs are shown in
Table 41. The results in red show where the measured values have exceeded the
thresholds for the injury criteria, and results in brown are 95% or greater of the criteria
limit.
The review of accident studies indicated that head protection is also the highest priority
for children travelling in forward facing non-integral CRSs, followed by chest protection.
The injury mechanism associated with these CRSs is head contact with parts of the
vehicle interior. The proposed limit for the head excursion of the dummy during testing
is currently 550mm.
The head excursion range in the tests with the Q3 was 65-79% of the threshold while
the range with the Q6 was 76-86% of the threshold and all had an excursion of well
below 500mm. The maximum head acceleration for the Q6 was 79% of the threshold for
the criterion, so there is scope for reducing the threshold for horizontal head excursion,
in line with the space available in the vehicle.
The limits for chest compression (33mm) were exceeded in the tests with the Q6
dummy, with a range from 106-112% of the proposed threshold. In the tests with the
low rated CRS and the high sales CRS the head of the dummy contacts the chest. This is
when the maximum chest compression occurs in these tests. It is unclear why the
smaller dummies have greater thresholds than the larger dummies.
The limits for chest compression are again taken from the work of EEVC WGs 12 & 18
(Wismans et al., 2008), modified for the position of deflection measurement sensors. In
this case, the scaling formula they used is as shown below.
Where
TRL
•• is the ratio of peak sternal deflection;
•y is the ratio of rib length;
••t is the ratio of calcaneal tendon failure stress; and
•Eb is the ratio of bone modulus.
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The variation of the scaling factor for the Q-series dummy ages is shown in (cross
reference to Table below).
Table 40: Scaling factor ratio for the sternal deflection measurements
Scaling
ratio
Q0
Q1
Q1.5
Q3
Q6
Adult
••
0.84
1.03
0.98
0.93
0.94
1
As with the head acceleration threshold scaling, each of the material property
parameters varies with age in a sensible manner. It is only the output of the scaling
formula which produces an unexpected progression. Here, the sternal deflection for a
one-year-old is greater than for the adult. When talking about the risk of AIS 3+ thoracic
injuries, it seems unlikely that a one-year-old can sustain more sternal deflection than
an adult without injury.
Instead, we can see that, based on the terms in the scaling equation, this scaling factor
relates to the risk of rib fracture. It may be that smaller children can sustain large
thoracic deformations before rib fracture occurs. However, the risk of AIS 3+ injury
needs to account for visceral injuries as well as those injuries to the rib cage. It is known
that younger persons can sustain visceral injuries without an associated rib fracture.
Therefore, it seems that these scaling ratios are probably unsuitable for use in relation to
all AIS 3+ thorax injuries caused by restraint system loading to the chest.
Chest injuries are an issue with older children and the mechanism is associated with the
adult belt loading the chest. More research is needed in this area to set appropriate
thresholds for the criterion.
In addition to the head and chest region, the abdomen is also a high priority area to
protect for children using non-integral CRSs, however there is nothing on the Q dummy
that measures this.
The injury mechanism associated with abdominal loading is “submarining” and loading
from the adult belt. The kinematics of ISOFix attached non-integral CRSs can be
different to the equivalent belt attached systems. With the belt attached systems, the
CRS moves forward into the adult lap and diagonal seat belt. With ISOFix attached
systems, the CRS is often held firmly in place against the vehicle seat back, so that only
the child moves forward into the adult belt system. With the latter event, there is likely
to be more potential for poor belt interaction and the possibility of an increase in
abdominal injuries. When the proposed procedures are extended to include non-integral
systems this will be a key area to monitor.
calculation of the forces measured in the lumbar spine and the lap belt. The suggestion
is that during the frontal impact the lumbar spine resultant of Fx and Fz shall not exceed
[undetermined] per cent of the lap belt force. The products assessed all achieved a ratio
of less than 55% apart from the product that was selected on the basis that it was
expected to perform poorly, which achieved a ratio of 94%. However, this product had
the lowest lap and diagonal belt loadings and lowest chest compression. So it is unclear
what this measurement is representing.
In all the tests with non-integral CRSs, the lap portion of the adult belt became wedged
into the gap at the top of the dummy legs (Figure 62). There are serious limitations with
the ability of the Q-series dummies to assess non-integral CRSs. It is essential that the
lap portion of the adult belt is able to take the path of travel over the dummy in the
same way that it would with a child. In addition to this, if a dummy is capable of
submarining, it should at least be detectable and ideally the extent should be
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measurable. For non-integral CRSs, where abdominal injuries are a priority, the P series
dummies even with their limitations may be a better option.
Figure 62: Non-integral CRSs, dummy and belt interaction
As stated earlier, the CRSs tested in this programme are considered as relatively safe
with respect to the likelihood of neck injuries occurring in real world accidents. However,
in all the tests with the Q3 in the non-integral CRSs, the dummy produced upper neck
tensile forces which exceed the proposed threshold (they were on average 179% of the
threshold). This limit relates to an expected 50 % risk of AIS • 3 neck injury (as scaled
for the child size; EEVC, 2008). Therefore it seems to be the case that the proposed
equipment, measurement tools or procedures do not lead to an accurate real world
injury risk for this body region.
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Table 41: Front impact results table – forward facing non-integral CRSs
Group II Child
Restraint Systems
ATD
Head Head
exc
exc
H
V
HIC15
Head
res ac
3ms
g
Upper
Neck
Fz
N
Upper
Neck
My
Nm
Lower
Neck
Fz
N
Lower Chest
Chest
Neck compre res acc
My
ssion
3ms
Nm
mm
G
Lap
belt
load
N
Lumbar Lumbar
FxFz
FxFz/
Res
lap
N
mm
mm
Limits
550
800
7801000
76
1364
61
N/A
N/A
38
55
N/A
N/A
N/A
Low rating
Monte Carlo
Q3
360
690
602
71
2375
15
919
98
31
42
1210
670
55%
High rating
Solution X-fix
Q3
434
748
378
61
2174
19
1104
110
32
36
1740
770
44%
High volume sales
Kidfix
Q3
361
621
562
72
2768
12
737
111
34
44
1810
770
43%
550
800
10831389
89
2304
118
N/A
N/A
33
55
N/A
N/A
N/A
Q6
443
753
506
70
2128
55
1480
171 data
clipped
35
45
1650
1550
94%
Q6
475
793
289
54
1487
38
1418
134
35
37
2740
1280
47%
Q6
418
784
356
60
2090
44
1308
161
37
40
3230
1410
44%
Low rating
Monte Carlo
High rating
Solution X-fix
High volume sales
Kidfix
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the upper neck. Therefore, if one was to assume a consistent injury threshold for tensile
force at the upper and lower neck, then the lower neck measurements would not provide
any additional information, when considering peak values.
Research, carried out by Luck et al. (2008) studied eighteen PMHS osteoligamentous
(bone and ligament, but not muscle) head-neck complexes, ranging in age from 20
weeks gestational to 14 years, which were tested in tension. The spines were cut into
three segments (C4-C5, C6-C7, and OC-C2). The results of the destructive part of the
tensile testing provided information to show that, for the older (> five months postnatal) cohort, the upper cervical spine was significantly stronger then the lower cervical
spine. This may support the implementation of a lower neck tensile force threshold which
is lower than the threshold at the upper neck. However, it is expected (based on FE
modelling; van Ee et al., 2000) that in adults, at least, the neck musculature adds
greater force tolerance to the lower neck than the upper neck. Based on their modelling
work, van Ee et al. suggested that consideration of the cervical musculature would shift
the predicted site of injury (under tensile loading) from the lower to the upper cervical
spine. However, the effect of musculature on neck strength may be much less in the
necks of children. This research, on the tolerance of human necks, should be taken into
account when proposing a tolerance criterion for the lower neck.
Based on the results from the frontal impact tests, it is evident that all of the CRSs pass
the flexion bending moment limits assessed at the upper neck, as proposed for use with
the new regulation. This is encouraging as neck injuries are not observed frequently in
the real world accident data. Therefore, these test results seem to support the notion
that current CRS designs are reasonably safe in terms of neck injury protection.
The upper neck extension moments are of a similar magnitude though no limit has been
set for these values. The work of Mertz et al. in developing Injury Assessment Reference
Values (IARVs) suggested that the tolerance to extension moments was just over half of
the flexion values. The extension value was based on the maximum moment tolerated in
sled tests with a volunteer (Mertz and Patrick, 1971). Adopting an upper neck extension
moment limit that was half of the flexion limit would result in failures for some of the
current CRSs tested with a Q1 dummy. It is suggested that the sense of the flexion to
extension relationship for use with dummies representing small children requires further
investigation before it could be adopted.
Currently the lower neck does not have bending moment criterion in the new regulation.
The measured lower neck bending moment peak values are significantly higher than the
upper neck. This difference means if the criteria limits for the upper neck were applied,
these limits would be exceeded. Instead of directly transferring the upper neck limit to
the lower neck, Mertz et al. (2003) proposed multiplying the upper neck threshold by a
factor of two to generate bending moment IARVs for the lower neck. If this approach
was applied to the results generated here, then a lower neck limit twice that of the upper
neck would allow all of the CRS to pass the criterion. However, the biomechanical basis
for adopting such an approach is limited.
The Mertz et al. suggestion was based on the recommendation from Prasad et al. (1997)
that the lower neck extension moment threshold for ligamentous damage to a mid-size
male adult would be in the range between 154 and 186 Nm. The ratio between the lower
value of this range and the corresponding Out-of-Position (OOP) peak extension moment
in use as an IARV for the Occipital Condyle (OC) / first cervical vertebra (C1) junction
(154 divided by 78) was approximately two. It should be noted that the Prasad et al.
range came from a very limited number of tests, with only two PMHS (Post-Mortem
Human Subjects) and one volunteer (Mertz and Patrick, 1967).
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C.4.2 Assessment of proposed protocols using an alternative pulse
As part of the front impact assessment, a small comparison was made with a more
severe pulse. The test speed proposed by the Informal Group, 50km/hr +0/-2, is
representative of the speed limit where most children have their injuries (see Section
A.4.1) on the roads. However, the pulse proposed (UNECE Reg.44), was developed in
the 1970s and may not be representative of the current vehicle fleet. The information
brought to the GRSP Informal Group showed full scale testing at higher speeds or with
an offset (see Section B.2.2).
The NHTSA website contains information on full scale tests at 50 km/hr with a full width
barrier, which is representative of the type of conditions that are needed to assess CRSs.
The crash data from these tests; for small family cars, family cars, superminis, executive
cars and sports cars, sold in Europe, was used to investigate the shape of a pulse that
would be more representative of the current vehicle fleet. A mean was calculated from
these pulses along with plus and minus 2g from the mean. This information was used to
create a new pulse corridor, which was higher than the pulse proposed by the Informal
Group (Figure 63). The coordinates of the higher severity pulse are shown in Table 42.
-50
S.Family
-46
Family
Supermini
-42
Sports
-38
Exec
Av.
-34
-2g
-30
g
/
n
io
ta -26
r
e
l
e
cc -22
A
+2g
Bottom Corridor
Top Corridor
-18
-14
-10
-6
-2
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
0.12
Time / s
Figure 63: NHTSA vehicle accelerations, 50km/hr, 100% overlap barrier test
Vehicles are much stiffer than they were when Reg.44 was being developed, so it is not
surprising that this pulse is higher in peak g than the Reg.44 pulse. Comparison with the
Reg.44 corridor shows that the new pulse has a peak of 25g-32g whereas the Reg.44
pulse has a peak 20-28g. The duration of the corridor is also shorter for the new pulse
with the deceleration ending between 85-100ms compared to 100-120ms for the Reg.44
pulse.
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Table 42: Front impact alternative pulse coordinates
Time
(ms)
Acceleration
Acceleration
(g)
(g)
0
5
0
7.5
-
45
25
32
60
25
32
85
0
-
100
-
0
Using this alternative pulse a small programme of tests were conducted to allow
comparison with the front impact results from the testing using the proposed pulse.
Figure 64 shows the acceleration traces for the tests that were carried out using the
higher pulse. For comparison, the acceleration traces for the earlier testing and the
proposed pulse are shown in the background, in grey.
Figure 64: Testing conditions using the higher pulse
The low rating restraints that had passed the injury criteria at the proposed pulse were
chosen to be used for this testing. The exception was the non-integral restraint, where
the low rating was not chosen as it had experience structural failures during testing at
the proposed pulse. It was assumed that this failure would occur at the higher pulse and
possibly invalidate any comparison of the results. Therefore the high sales restraint was
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chosen, as this was shown to be the next poorest performer from the front impact tests.
The assessment matrix for this testing is shown in Table 43.
Table 43: Assessment Matrix to assess the effects of an alternative pulse
Pulse
ATD
Tests
Group 0+ low rating
Babymax
Alternative
pulse
Q1
1
Q1.5
1
Group I low rating
Cosmo
Alternative
pulse
Q1
1
Q3
1
Group II low rating
Kidfix
Alternative
pulse
Q3
1
Q6
1
Table 66 shows that the higher pulse has a steeper rise for a longer time and a flatter
area around the peak compared to the proposed pulse. The figure also shows that
although the peak g sled pulse was fairly consistent (26.5g), two of the tests dropped
below the lower corridor at around 65ms.
The stopping distances for these tests are shown in Table 44. This shows that the
stopping distance was an average of 117mm shorter than in the tests with the proposed
pulse, which corresponds to the decrease in time duration of the pulse corridors.
Table 44: Stopping distance comparison
Stopping
ATD
Group 0+ low rating
Q1
Q1.5
527
520
Cosmo
Q1
Q3
Group II high sales
Q3
525
Kidfix
Q6
525
Mean
524
Mean
641
Babymax
Group I low rating
Reg.44 pulse
Distance (mm)
534
510
The results of the assessment with the rearward facing integral CRSs at the higher pulse
are shown in Table 45. The results in red show where the measured values have
exceeded the thresholds for the injury criteria, and results in brown are those close to
exceeding the criteria limit (95% of the limit).
The results show that with the exception of neck moments and chest compression, both
of which are well below the criteria limit, the other injury criteria have all significantly
increased in comparison to the tests using the proposed pulse.
As previously mentioned the main body region to protect for rearward facing restraints is
the head. This means head accelerations and excursions should be kept to a minimum.
The Q1 dummy head resultant acceleration is now very close to the criteria limit (97% of
the limit). The horizontal excursion of the dummy’s head has increased by 12%, but is
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still well below the limit (78% of the limit). The dummy exceeds the injury criteria limit
for both the upper neck force (128%) and chest resultant acceleration (105%).
The injury criteria results for the important body regions to protect did increase for the
test with the larger dummy. The Q1.5 dummy head resultant acceleration increased by
19%, to 66% of the limit. The horizontal head excursion increased by 16%, to 80% of
the limit. The Q1.5 chest resultant acceleration also increased by 22%, to 91% of the
limit.
These results show that the increase in pulse severity has had a significant effect on the
important body regions to protect for both the tested dummies. The horizontal head
excursions have increased to exceed the forward facing limit (550mm) with the larger
dummy. However the effect on the smallest occupant for this type of restraint (Q0)
should also be evaluated prior to the changing of any limits if this more severe pulse was
to be adopted.
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Table 45: Higher pulse tests – Rearward facing integral CRSs
Child Restraint
System
Pulse
ATD
Proposed limits
Head Head
HIC15
exc H exc V
mm
mm
700
800
Head
Upper
Lower
Chest
Upper
Lower
Chest
res ac
Neck
Neck
res acc
Neck Fz
Neck Fz
compression
3ms
My
My
3ms
g
N
Nm
N
Nm
mm
g
491629
72
1201
53
N/A
N/A
40
55
Group 0+ low rating
Proposed
Babymax
Q1
485
658
216
49
650
9
N/A
N/A
5
37
Group 0+ low rating Alternative
Babymax
pulse
Q1
544
665
502
70
1542
15
N/A
N/A
6
58
700
800
578741
76
1364
61
N/A
N/A
38
55
Proposed limits
Group 0+ low rating
Proposed
Babymax
Q1.5
483
579
158
42
728
11
N/A
N/A
4
41
Group 0+ low rating Alternative
Babymax
pulse
Q1.5
560
685
252
50
919
12
N/A
N/A
6
50
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The results of the assessment with the forward facing integral CRSs at the higher pulse
are shown in Table 46. The results in red show where the measured values have
the criteria limit (95% of the limit).
The main body region to protect for children travelling in forward facing integral
restraints is the head, specifically head contact with the vehicle’s interior. This means
that both head accelerations and excursions should be kept to a minimum.
The data show that in the Q1 exceeds the HIC limit (150% of the limit), although there
was no head contact. The chest resultant criteria limits (104%), as well as exceeding the
limit of the upper neck force by 66%, which was also exceeded during the test with the
proposed pulse. In addition the head resultant acceleration is also nearly exceeded (99%
of the limit).
The Q3 exceeds the head vertical excursion limit as well as exceeding the limit of the
upper neck force, which was also exceeded during the test with the test with the
proposed pulse. In addition the chest resultant increased by 43% (91% of the limit) and
the head resultant acceleration increased by 19% (99% of the limit) and are close to
exceeding the limits.
These results show that in addition to exceeding the neck force criteria limit, the criteria
limits of the important body regions, the head and chest are also exceeded. Although the
head horizontal excursions increased they are well below the limit. However the larger
dummy does exceed the vertical excursion limit.
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Table 46: Higher pulse tests – Forward facing integral CRSs
Child Restraint
System
Pulse
ATD
Proposed limits
mm
mm
550
800
Head
Upper
Lower
Chest
Upper
Lower
Chest
res ac
Neck
Neck
res acc
Neck Fz
Neck Fz
compression
3ms
My
My
3ms
g
N
Nm
N
Nm
mm
g
491629
72
1201
53
N/A
N/A
40
55
Group I low rating
Cosmo
Proposed
Q1
344
682
585
60
1636
18
N/A
N/A
20
43
Group I low rating
Cosmo
Alternative
pulse
Q1
383
698
943
72
1993
18
N/A
N/A
22
57
Proposed limits
550
800
7801000
76
1364
61
N/A
N/A
38
55
Group I low rating
Cosmo
Group I low rating
Cosmo
‡
Head Head
HIC15
exc H exc V
Proposed
Q3
462
799
414
63
2540
10
1106
123
28
35
Alternative
pulse
Q3
490
818
678
75
3012
16
1567
146
6‡
50
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C.4.2.3 Forward facing non-integral restraints
The results of the assessment with the forward facing non-integral CRSs at the higher
pulse are shown in Table 47. The results in red show where the measured values have
the criteria limit (95% of the limit).
The main body region to protect for forward facing non-integral restraints is the head,
specifically due to head contact with the vehicle’s interior and the abdomen, due to poor
interaction with the lap section of the seat belt. This means head accelerations and
excursions should be kept to a minimum. However there is not a validated method to
measure abdomen loading with the Q-series dummies.
The data show that the Q3 test exceeds the limit of the upper neck force, which was also
exceeded during the test with the proposed pulse, and nearly exceeds the head resultant
acceleration criteria limit (95% of the limit). However this remains the same as during
the test with the proposed pulse. Although the excursions of the Q3 increase by around
15%, the head and chest resultant accelerations (88% of the limit) remain similar to
those recorded in the test with the proposed pulse.
The Q6 exceeds the upper neck force criteria (115%) as well as exceeding the limit of
the chest compression (121%), which was also exceeded during the test with the
proposed pulse. The Q6 results show a 15-25% increase in injury criteria results and a
5% increase in head excursions.
The results show that the Q3 was not significantly affected by the increase in pulse
severity, with the same criteria exceeding the limits as the proposed pulse. The results
from the Q6 show a more significant effect on the important body regions. However only
the neck force criteria limit is exceeded.
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Table 47: Higher pulse tests – Forward facing non-integral CRSs
Child Restraint
System
Group II high
volume
Kidfix
Group II high
volume
Kidfix
Group II high
volume
Kidfix
Group II high
volume
Kidfix
§
Pulse
ATD
Head Head
HIC15
exc H exc V
Head
res ac
3ms
Upper Upper Lower Lower
Neck Neck Neck Neck
Fz
My
Fz
My
Chest
Lumbar
Chest
Lumbar
res acc
FxFz/
compression
FxFz Res
3ms
lap
g
N
Nm
N
Nm
mm
g
N
7801000
76
1364
61
N/A
N/A
38
55
N/A
N/A
621
562
72
2768
12
737
111
34
44
770
43%
421
716
597
72
2587
18
901
137
7§
44
1190
45%
Proposed limits
550
800
10831389
89
2304
118
N/A
N/A
33
55
N/A
N/A
Proposed
Q6
418
784
356
60
2090
44
1308
161
37
40
1410
44%
Alternative
pulse
Q6
437
767
654
75
2638
41
1274
172
40
45
1640
57%
mm
mm
Proposed limits
550
800
Proposed
Q3
361
Alternative
pulse
Q3
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C.4.3 Future work
Initial discussions in the Informal Group have been made as to whether a Global
Technical Regulation (GTR) for front impact could be possible. This would look to
creating a harmonised front impact test procedure for child restraint testing throughout
the world. Investigating this was outside the scope of this project however a comparison
of the pulses is shown in Figure 65. Investigation would have to be conducted as to
whether this corridor is also still representative of modern vehicles in the USA.
Figure 65: FMVSS 213 front impact pulse corridor, compared to new regulation
pulse corridors
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C.4.4 Front impact summary
During the front impact tests of the rearward facing integral restraints with the proposed
pulse, none of the injury criteria limits were exceeded. However the smaller dummy (Q1)
did exceed the head and chest resultant acceleration criteria in the tests with the higher
pulse. The measured horizontal head excursions from all the rearward facing restraint
tests were well below the 700mm limit, and only one test exceeded the forward facing
excursion limit of 550mm.
It therefore could be suggested that if improved restraint performance is desired as a
result of implementing the new regulation, that the currently proposed limits could be
reduced. Depending on whether the higher severity pulse is adopted or not, will
influence by how much the limits should be reduced. Either way the results show that
the horizontal head excursion can be significantly reduced, to at least 550mm. This
would then harmonise the limit with the forward facing limit. It can also be argued that
in a vehicle a rearward facing restraint would not have any larger space in front of it
than a forward facing restraint, so why are the limits different?
It should also be remembered that eventually belt attached restraint will also be
approved by this regulation and that they will struggle to match the same excursions as
the ISOFix seats. However this could be solved by using a different excursion limit for
belt attached seats or just encourage belt restraint design to improve.
If the higher pulse was adopted, tests with the smallest dummy (Q0) should be
conducted before revising the limits, as the smallest dummy has the largest
accelerations at the lower severity pulse.
During the front impact tests of the forward facing integral restraints with the proposed
pulse, one restraint failed the head acceleration resultant criteria, but all restraints failed
the upper neck force criteria with both dummies. This leads to questioning whether the
limits for the upper neck are realistic. However during the tests with the higher pulse the
smaller dummy (Q1) did exceed the resultant acceleration criteria limit and also comes
close to exceeding the head resultant acceleration criteria limit. All tests exceeded the
upper neck force criteria limit.
The measured horizontal head excursions from all the forward facing restraint tests were
well below the 550mm limit, in all the tests with the proposed pulse and the higher
pulse. One restraint did exceed the vertical excursion limit in the higher pulse tests, after
nearly exceeding it in the test with the proposed pulse.
Therefore it could be suggested that to improve restraint performance that some of the
currently proposed limits could be reduced for forward facing restraints. The results show
that the horizontal head excursion can be reduced to 500mm, which would be in line
with the limit for forward facing integral restraints in Reg.44. The criteria limits when
using the proposed pulse could also be reduced to encourage design improvement.
However if the higher pulse is to be used, the criteria limits for head and chest
accelerations look around the right level.
Again it should be remembered that eventually belt attached restraint will also be
approved by this regulation and that they will have a vast disadvantage over ISOFix
seats, especially in terms of excursions. However again this could be solved by using a
different excursion limit for belt attached seats.
C.4.4.3 Non-integral restraints
During the front impact tests of the forward facing non-integral restraints with the
proposed pulse, all the restraints exceeded the upper neck force criteria with the
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smallest dummy (Q3) and the chest compression criteria with the largest dummy (Q6).
Neither of these body regions were identified as being extremely important to protect by
the accident research and the consistency at which they were both exceeded by all the
restraints leads to questioning the criteria limits.
The measured horizontal head excursions from all the non-integral restraints tests were
well below the 550mm limit, with the largest excursion measured at 475mm. The higher
pulse tests did not seem to have a significant effect on the injury criteria for the smaller
dummy. Whereas the injury values of the larger dummy did significantly increase,
however only the upper neck criteria limit was exceeded (in addition to the chest
compression).
Therefore it could be suggested that the injury criteria limits could be reduced for both
dummies for this type of restraint. Further investigation of the chest compression limit
and the upper neck force criteria needs to be conducted. The possibility of introducing
lower neck criteria should also be researched. The abdominal protection of the restraint
could also not be properly assessed, the proposed method of using the lower lumbar
loads as a proportion of the lap belt load needs further investigation. The abdomen was
identified as an important body region to protect and therefore it is essential that a
robust method for assessing this is devised.
The horizontal head excursion limit could also be revised as all dummies were well below
the 550mm limit. However it should be remembered that the largest dummy (Q10.5)
was not tested, as it is not currently available, and it is likely to have the greater
excursions. Though a different head excursion limit could be set for this dummy, as in
the current Reg.44.
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C.5 Assessment of rear impact proposals
C.5.1 Introduction
The rear impact test programme was designed to assess the rear impact procedure
proposed by the GRSP Informal Group (see Section 0). The test speed and pulse
proposed by the Informal Group remains the same as for Reg.44, with a speed of 30
km/h +0/-2 and using the deceleration envelope in Section B.3.2. The main differences
between UNECE Reg.44 and the proposal for the new regulation are the test bench and
the dummies. The test programme was designed to gain an understanding of the relative
effect of the geometry and cushion properties of the new proposed test bench on the
performance of CRSs compared to those of the test bench specified in Reg.44 and to
assess the implications of using the Q-series ATD criteria and limits, proposed by the
Informal Group.
proportion of rear impact accidents involving children and the head was shown to be the
priority body region for protection. The injury mechanisms that cause these head injuries
are not well defined, however it is presumed that these will be similar to those that
cause injuries to rearward facing children in front impact. Injuries to the neck and
abdomen were also shown to be present, though only a small number of accident cases
were included in the data analysis.
C.5.2 Effect of the proposed test bench
The test matrix for the assessment of the effect of the proposed test bench on the
performance of CRSs, compared to those of the Reg.44 test bench is shown in Table 48.
The assessment used a different size of P-series dummy with each of the two models of
CRS. Each CRS was tested using the two different test bench set-ups; the new proposed
test bench (detailed in Section B.1) and the current Regulation 44 test bench. The CRS
models represent seats that received low or high ratings in various consumer tests.
Table 48: Rear impact assessment matrix – test bench evaluation
Group 0+ Child Restraint
Systems
Test Bench
ATD
Tests
Low rating
Babymax
Proposed
P1.5
1
Reg.44
P1.5
1
High rating
Babysafe
Proposed
Reg.44
P0
P0
1
1
An example of the rear impact test setup is shown in Figure 66. The photograph has
been edited digitally, to remove the labels and logos from the CRS.
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Figure 66: Rear impact test
The results of the assessment with the rearward facing integral CRSs are shown in Table
49. The P-series dummy instrumentation is very limited and therefore only a few injury
criteria can be compared, using the limits specified in Regulation 44. The P0 has no
instrumentation and therefore the comparison is limited to the horizontal and vertical
head excursions, as well as any noted differences as a result of the difference in test
bench geometry.
The P1.5 was instrumented to the requirements of Regulation 44; a 3-axis accelerometer
in the thorax, allowing the chest resultant to be compared, along with the chest vertical
negative acceleration. This means that the injuries to the high risk body region, namely
the head, are assessed by looking at the dummy head excursions. The body regions
mentioned, considered as less important to protect, namely the neck and abdomen are
not measured with the P dummy.
The Reg.44 assessment limits are shown in Table 49 along with the results comparing
the new proposed test bench with the Reg.44 test bench.
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Table 49: Rear impact results table - test bench evaluation
Group 0+ Child
Restraint Systems
ATD
Bench
Head
Head
Head
F-G
D-E
exc V
plane
plane
mm
High rating
Babysafe
High rating
Babysafe
Low rating
Babymax
Low rating
Babymax
Chest
Chest Z
res acc
acc 3ms
3ms
g
g
Reg.44
Limits
F-G
800
D-E
N/A
N/A
P0
New
Pass
533
Pass
N/A
N/A
P0
Reg.44
Pass
563
Pass
N/A
N/A
Reg.44
Limits
F-G
800
D-E
55
30
P1.5
New
Pass
637
Pass
38
33
P1.5
Reg.44
Pass
647
Pass
24
14
Although the vertical head excursion measurements were within the limits of Reg.44, the
vertical excursion was less in the tests on the newly proposed test bench. The F-G and
D-E planes (see Figure 56) are not exceeded by the head of the dummy during any of
the tests. However during both the tests with the P1.5 dummy in the low rated CRS, the
top of the dummy’s head came very close to contacting the test bench cushion and the
handle of the CRS. The adjustable recline mechanism of the head pad broke and rose up
allowing extra slack in the harness, as it was pulled through the head pad. The head pad
recline mechanism of this CRS broke in all rear impact tests.
The results with the P1.5 also show that the chest resultant and chest vertical were both
higher in the test on the new regulation bench. The chest vertical negative 3ms
maximum exceeded the Reg.44 limit in the test with the P1.5, on the new test bench.
This may be due to a number of contributing factors:
The stiffness of the proposed cushion is greater than that of the Reg.44 cushion.
There is a 5o difference in the angle of the backrest (Reg.44 20o, new bench 25o).
The difference in angle meant that the CRS on the new bench was able to rotate more
during the impact test and lift up further from the test bench base cushion (Figure 68).
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Reg.44 test bench
New regulation test bench
Figure 67: Test bench comparison
During the test with the new bench the feet of the dummy get caught under the rebound
handle of the infant carrier, whereas in the Reg.44 bench test the feet slipped above the
handle. This combined with the extra slack introduced in the harness, by the head pad
lifting up, enabled the dummy’s bottom to slide towards the cushion. This difference in
the kinematics of the dummy in the two tests can explain the variation in chest vertical
accelerations and as a result, the difference in chest resultant accelerations. The new
test bench cushion has been proposed as more representative of current vehicle seats
and with this being the case, it seems that the stiffness and the angles of the test bench
cushions have an effect on CRS performance. CRSs assessed on this new test bench
may, as a result, perform better over a wider range of vehicles.
Reg.44 test bench
New regulation test bench
Figure 68: P1.5 test comparison
The ISOFix anchorages in the tests using the proposed bench had to be moved forward
to allow the low rated CRS to be installed The CRS design was incompatible with the new
test bench. For the test using the Regulation 44 bench, although the anchorages were in
the maximum rearward position, the backrest angle and softer cushion still allowed the
CRS to be attached.
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C.5.3 Evaluation of proposed dummy performance criteria
The test matrix for the practical assessment of the effects of the proposed rear impact
procedure on rearward facing integral CRSs is shown in Table 50. The assessment used
three dummies with the high volume sales CRS and the largest and smallest dummy
with the high rating and low rating CRSs.
Table 50: Rear impact assessment matrix – test bench evaluation
Systems
Test Bench
Low rating
Babymax
Proposed
High rating
Babysafe
Proposed
High volume
Cabriofix
Proposed
ATD
Tests
Q0
Q1.5
1
1
Q0
1
Q1.5
1
Q0
Q1
1
1
Q1.5
1
The results of the assessment with the rearward facing integral CRSs are shown in Table
51. The accident review showed that the head is the priority body region to protect in
rear impact. The injury mechanisms that cause these head injuries in rear impact are not
well defined, however it is presumed that these are caused by contact with the vehicle
interior. It is therefore important that the horizontal and vertical head excursions of
dummies are at a minimum. The results show that all the head vertical excursion
measurements are within the required limit and that the F-G and D-E planes (see Figure
56) are not exceeded by the head of the dummies during any of the tests.
However the low rating and high rating CRS both fail the head resultant acceleration
requirement with the Q0 dummy. In both tests, the initial head resultant acceleration is
well below the limit (25-42g), however during the rebound phase, when the dummy falls
back into the CRS, its head impacts the back of the head pad and a large spike is seen in
the head resultant, exceeding the 85g 3ms limit. Both these CRSs have a plastic
adjustable head pad, which has minimal padding behind the head of the dummy to
cushion the dummy’s head as it lands back into the CRS. The current regulation does not
use instrumentation in the head of the dummies during approval and therefore this
problem of high accelerations in rear impact would not be identified during current type
approval of the CRSs.
The recorded chest resultant acceleration in the high rated CRS with the smallest dummy
was also very close to exceeding the limit. Again the initial chest resultant acceleration
was well below the limit (•30g), however during the rebound phase, when the dummy
lands back down in the CRS a large spike was seen in the chest resultant and was on the
55g limit.
The results from the high volume sales CRS, which was tested with all three dummy
sizes shows that the smallest dummy recorded the highest accelerations in the head,
chest and pelvis, which agrees with the philosophy that testing with the smallest dummy
will be the worst case test in terms of dummy loading. The P0 dummy, currently used for
type approval, has no instrumentation, so loading is not currently measured for the
smallest dummy. However the largest dummy did have the highest neck forces and
moments, which is probably due to its larger head mass.
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Injuries to the neck were also found to occur in the rear impact review. All the neck force
and moment recorded values were well below the current specified limits. The accident
review showed a very small number of abdominal injuries. However it is not possible to
ascertain whether the CRSs protect the dummy from abdomen injuries in rear impact
It should be noted that the high rating CRS may have had an unrealistically good result,
when tested with the largest occupant certainly from comparing the chest and pelvis
resultant time histories to those of the other CRSs. This is because during the test, the
foot of the support leg got caught under the base plate of the test bench cushion and
acted as a 3rd attachment point, limiting the rotation of the CRS and then holding the
CRS in the air as the dummy landed back into it, thus reducing the rebound of the
dummy.
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Table 51: Rear impact results table - criteria evaluation
Group 0+ Child
Restraint Systems
Low rating
Babymax
High rating
Babysafe
High volume sales
Cabriofix
High volume sales
Cabriofix
Low rating
Babymax
High rating
Babysafe
High volume sales
Cabriofix
TRL
ATD
Head
Head exc.
Head
HIC15
F-G plane V (mm) D-E plane
Head
resultant
accel (g)
Upper
neck
Fz (N)
Upper
Chest
neck My compression
(Nm)
(mm)
Chest
resultant
accel (g)
Limits
F-G
800
D-E
671
85
546
17
N/A
55
Q0
Pass
492
Pass
407
86
423
2
N/A
43
Q0
Pass
490
Pass
567
104
295
5
N/A
55
Q0
Pass
514
Pass
147
50
436
7
N/A
45
Limits
F-G
800
D-E
629
72
1201
53
40
55
Q1
Pass
650
Pass
131
40
752
19
6
32
Limits
F-G
800
D-E
741
76
1364
61
38
55
Q1.5
Pass
650
Pass
68
33
640
16
7
37
Q1.5
Pass
693
Pass
84
32
707
17
6
25
Q1.5
Pass
674
Pass
132
39
861
23
6
40
130
CPR821
C.5.4 Rear Impact Summary
The rear impact test programme was designed to assess the rear impact procedure
proposed by the GRSP Informal Group. The test conditions proposed remain the same as
for Reg.44. The main differences between UNECE Reg.44 and the proposal for the new
regulation are the test bench and the dummies. This rear impact test programme was
designed to gain an understanding of the relative effect of the geometry and cushion
properties of the new proposed test bench on the performance of CRSs and to assess the
implications of using the Q-series ATD criteria and limits, proposed by the Informal
Group.
in rear impacts. The injury mechanisms that cause these head injuries are not well
defined. Injuries to the neck and abdomen were also shown to be present, though these
only represented a small number of accident cases in the data analysis.
An assessment using the P series dummies was carried out to gain an understanding of
the relative effect of the geometry and cushion properties of the proposed test bench on
the performance of CRSs. The P-series dummy criteria were compared using the two test
environments and the limits specified in Regulation 44. The P0 represents a new born
child. It has no instrumentation and therefore the comparison is limited to the horizontal
and vertical head excursions.
The P1.5 was instrumented to the requirements of Regulation 44. Chest resultant and
chest vertical acceleration were compared using the instrumentation and potential
injuries to the head were compared by looking at the dummy head excursions.
The vertical excursion was seen to be less in the tests on the newly proposed test bench.
However, the proposed test bench allowed more rotation of the CRSs, towards the
seatback, allowing more movement of the dummy. The results showed increased
resultant and vertical chest accelerations. This may be due to the greater stiffness of the
proposed cushion and the increased angle of the backrest.
The stiffer foam of the proposed test bench made it impossible to connect the ISOFix
attachments to the test bench anchorages, with one of the CRSs. The anchorages on the
test bench were moved forward to complete the test programme. If a CRS design is
incompatible with the new test bench, then it may have compatibility issues in the field.
bench.
An evaluation was carried out to assess the implications of using the Q-series ATD
criteria and limits, proposed by the Informal Group. The accident review showed that the
head is the priority body region to protect in rear impact. The injury mechanisms that
cause these head injuries in rear impact were not well defined. The P0 dummy does not
have the capability of measuring head acceleration and this is not assessed in current
type approval of CRSs. However, during this evaluation, two of the CRSs tested with the
Q0 dummy failed the limits proposed for the 3ms head resultant acceleration
requirement. If the Q series dummies were used as a measurement device in type
approval testing of CRSs, the head accelerations could be assessed and this may lead to
safer CRSs for young babies. The P0 has no capability to measure chest acceleration and
this is not assessed, with the smallest dummy, in current type approval testing of CRSs.
The resultant chest acceleration was on the limit of the proposed criteria with the Q0 in
TRL
131
CPR821
the high rated CRS. Again, if the Q series dummies were used in type approval testing
and chest acceleration could be assessed, this may lead to safer seats for new born
children.
test in terms of dummy loading. This suggests that type approving with the smallest
dummy instrumented could lead to safer CRSs.
Injuries to the neck were also found to occur in the rear impact review. The largest
dummy had the highest neck forces and moments, which is probably due to its larger
head mass. All the neck force and moment recorded values were well below the
proposed limits.
The accident review showed a very small number of abdominal injuries. It is not possible
to ascertain whether the CRSs protect the dummy from abdomen injuries in rear impact
TRL
132
CPR821
C.6 Assessment of side impact proposals
C.6.1 Introduction
apply and it will improve the safety of CRSs. This practical assessment programme was
designed to assess the proposed procedure for repeatability and reproducibility.
The test procedure was assessed for repeatability based on three repeat tests of some of
the CRSs evaluated. Reproducibility of the test procedure was also evaluated by
comparison with the results of six side impact tests (three with a rear facing integral CRS
(Group 0+) and three with a forward facing integral CRS (Group I) at the Dorel test
facility in Cholet, France.
Furthermore, the procedure was assessed to evaluate the effect of applying the front
impact injury criteria to side impact and to evaluate, where possible, how the dummy
loading in the procedure relates to loading in the vehicle.
Finally, the effect of varying friction in the ISOFix anchorage, on dummy loading, was
evaluated.
C.6.2 Anchorages
The ISOFix anchorage and top tether locations for the side impact testing proposal are
located at the positions shown previously, in Table 16. The side impact proposal uses
the G1 top tether position only.
The side impact test bench proposal does not include belt anchorage locations. However,
as booster seats were included in the TRL test programme these anchorages have been
incorporated into the sled design. The anchorage locations were as described in Section
B.1.4, with the exception of the lower inner (seat-belt buckle) location, which had to be
moved forward in the y-axis, to prevent interference with the sliding ISOFIX anchorages.
Table 52: Side impact anchorage locations
Direction
x
y
z
Upper (D-ring)
-240
-250
-630
Lower (buckle)
10
200
59
Lower (outer)
10
-200
14.5
Belt anchorage locations
C.6.3 Test conditions
Figure 69 and Figure 70 show the sled velocity change for the 28 side impact tests
performed at TRL (including forward facing, rear facing, and anchorage friction tests)
and the six tests performed at Dorel. It can be seen that the change of velocity was
close to the middle of the target corridor for the TRL and the Dorel tests, and that the
repeatability is very good. The velocity change at approximately 20 ms was slightly later
and sharper in the TRL tests than in the Dorel tests, but overall the reproducibility of the
pulses between the two laboratories was good. The range of TRL sled velocity is wider as
it contains all the tests carried out at TRL, across a much wider range of CRSs.
TRL
133
CPR821
30
28
26
24
Velocity (km/hour)
22
20
18
16
14
12
10
8
6
4
2
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.07
0.08
Time (s)
Figure 69: TRL sled velocity data (28 tests)
30
28
26
24
Velocity (km/hour)
22
20
18
16
14
12
10
8
6
4
2
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Time (s)
Figure 70: Dorel sled velocity data (6 tests)
TRL
134
CPR821
Figure 71 and Figure 72 show the sled deceleration pulses for the TRL and Dorel tests.
Also shown are the time intervals over which the door contacts the CRS (estimated from
the videos), and in which the peak head and chest resultant accelerations occur.
Figure 73 shows the same data for the TRL reproducibility tests for direct comparison
with the Dorel results in Figure 72.
The different shape of the elbow in the velocity plots is reflected in the acceleration
plots. The TRL pulse has a flatter, more consistent 2 g pulse in the first 150 ms, followed
by a steeper rise in the acceleration to approximately 13 g. The last part of the pulse,
however, is less consistent, with peak accelerations ranging from 11 to 16 g. This occurs
about the time that the sled velocity reaches zero and changes direction to rebound. This
part of the pulse partially overlaps the time frame during which the resultant head
accelerations reached their maximum value. However, the variation in sled acceleration
does not seem to have influenced the repeatability of this measure.
The Dorel sled pulse has a notably less steep rise in acceleration to the plateau at 13 g.
CRS-to-door contact occurs markedly earlier (20-22 ms) in the Dorel tests than in the
TRL tests (25-35 ms). Maximum resultant chest acceleration occurs slightly earlier in the
Dorel tests, and maximum resultant head acceleration occurs much earlier in the Dorel
tests than the TRL tests (45-50 ms and 50-60 ms respectively).
18
16
14
Sled deceleration ( g)
12
10
8
6
4
Max chest
resultant
acceleration
CRS-Door
Contact
2
Max head
resultant
acceleration
0
0
-2
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Time (s)
Figure 71: TRL sled deceleration data (28 tests)
TRL
135
CPR821
Figure 72: Dorel sled deceleration data (6 tests)
18
16
14
Sled deceleration ( g)
12
10
Max head
resultant
acceleration
8
6
4
Max chest
resultant
acceleration
CRS-Door
Contact
2
0
0
-2
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Time (s)
Figure 73: TRL sled deceleration data (6 reproducibility tests only)
TRL
136
CPR821
C.6.4 Restraint system loading
C.6.4.1 Comparison with observation of full scale testing
The phasing of the loading to the CRS will have an effect on the loading to the child. TRL
have analysed this sequence of loading from full scale tests.
The side of the struck vehicle is loaded by the striking vehicle and within 20ms the
velocity of the intrusion into the vehicle is in excess of 30km/hr. At this point the chassis
velocity of the struck vehicle is about 5km/hr. The chassis velocity of the struck vehicle
builds relatively slowly and the velocity of the intrusion slows down and meets the rising
chassis velocity at about 60ms.
vehicle chassis, however it does not reproduce the speed of the intrusion into the struck
vehicle.
When the side of the struck vehicle starts to intrude into the interior of the vehicle, it
loads the firstly vehicle seat and then the CRS. The CRS goes on to load the dummy. The
intruding structure continues to load both the vehicle seat and the CRS. The dummy’s
thorax is loaded, through the CRS and then the dummy’s head moves over the top of the
intruding structure (supported by the side wing of the CRS). The intruding structure
remains in contact with the vehicle seat and the CRS at maximum dynamic intrusion.
The intrusion diminishes slightly when the vehicles part and the vehicle seat remains
with the intrusion panel. As the intrusion diminishes the belt attached CRS moves away
from the vehicle seat, in the direction of the vehicle centre. It is expected that an ISOFix
CRS would remain with the vehicle seat. At no point does the vehicle seat lose contact
with the intruding structure.
This is very different to the events of the proposed test procedure, where the ISOFix
anchorages are allowed to move away from the intrusion panel.
C.6.4.2 Stopping distance
Table 54 to Table 56 show the sled impact velocity, stopping distance and anchorage
displacement for the TRL tests, and this information is summarised in Table 53. It is
clear from these tables that the impact velocity and stopping distance were very
repeatable throughout the testing. As noted in Section B.4.3, there is no tolerance on
the stopping distance, but a specification of 295 to 300 mm was used for calibration
runs. The upper limit for the calibration runs was set to 300 mm in order to ensure that
the intended intrusion was not exceeded. Despite this, the stopping distance in testing
ranged from 293-305 mm, including five tests that exceeded 300 mm stopping distance
and which would therefore have experience slightly greater intrusion than was intended.
The sled velocity and stopping distance in the side impact tests are similar to those in
the Reg.44 rear impact tests, which have a specification on the stopping distance of
275±20 mm in calibration runs and 275±25 mm in testing. The stopping distances in the
TRL side impact tests were clearly well within these limits, and would easily have met a
requirement of 300±10 mm. Nevertheless, the stopping distance may be more critical
for the side impact test procedure, compared to the rear impact procedure, because it
directly influences the intrusion of the door. It is recommended that the tolerance on the
stopping distance is considered further, particularly with respect to the level of intrusion
applied to the CRS.
TRL
137
CPR821
Table 53: Summary of TRL test conditions and anchorage displacement
Mean
Max
Min
SD
CV
Impact
velocity
(km/h)
26.05
26.14
25.91
0.06
0.2%
Stopping
distance
(mm)
298
305
293
3.21
1.1%
Anchorage
displacement
(mm)
36.4
65.0
3.0
17.6
48.3%
Table 54: Summary of TRL test conditions and anchorage displacement - rear
facing integral CRSs
Dummy
Impact
velocity
(km/h)
Stopping
distance
(mm)
Anchorage
disp.
(mm)
Q1.5
26.03
295
52
Q1.5
26.02
293
45
Q1.5
26.04
299
42
High rating
Babysafe
Q0
26.13
300
6
High rating
Babysafe
Q1
26.10
298
6
High rating
Babysafe
Q1.5
26.06
297
3
High rating
Babysafe
Q1.5
26.10
296
3
Q1.5
26.10
294
33
Q1.5
26.10
300
N/A
Group 0+
CRSs
Low rating
Babymax
Low rating
Babymax
Low rating
Babymax
Mean
disp.
(mm)
Comment
46.3
5.0
Modified CRS
(degraded)
High volume
sales
Cabriofix
High volume
sales 3
Belt attached only
Cabriofix
TRL
138
CPR821
Table 55: Summary of TRL test conditions and anchorage displacement forward facing integral CRSs
Group I CRSs
Low rating
Cosmo
Low rating
Cosmo
Low rating
Cosmo
High rating
Priorifix
High rating
Priorifix
High volume
sales Iseos
High volume
sales Iseos
High volume
sales 2 Duo
High volume
sales 2 Duo
Dummy
Impact
velocity
(km/h)
Stopping
distance
(mm)
Anchorage
disp.
(mm)
Q1
26.08
300
50
Q1
26.11
295
36
Q1
26.14
305
62
Q1
26.08
293
51
Q3
26.02
293
65
Q1
26.09
301
51
Mean
disp.
(mm)
Comment
49.3
58.0
46.5
Q3
25.98
301
42
Q1
26.06
302
40
Q3
25.99
296
38
39.0
Table 56: Summary of TRL test conditions and anchorage displacement forward facing non-integral CRSs
Dummy
Impact
velocity
(km/h)
Stopping
distance
(mm)
Anchorage
disp.
(mm)
Q6
26.05
296
34
Q6
26.04
300
36
Q6
26.05
302
33
Q3
25.95
300
28
Q6
26.08
298
16
High volume
sales Kidfix
Q3
25.91
297
27
High volume
sales Kidfix
Q6
Group II/III
CRSs
Low rating
Jane
Low rating
Jane
Low rating
Jane
High rating
Cybex
High rating
Cybex
TRL
Mean
disp.
(mm)
Comment
34.3
22.0
28.5
26.06
300
139
30
CPR821
C.6.4.3 Anchorage displacement
Although the impact velocity and stopping distance were very repeatable, the anchorage
displacement was very variable in the TRL tests, ranging from 3 to 65 mm across all of
the tests, and with a range of 49, 27, and 20 mm for the Group 0+, I and II/III seats
respectively. The largest range of anchorage displacements for a single seat was 26 mm
(36-62 mm, Group I low rating Cosmo). In contrast, the high rating Babysafe Group 0+
seat translated only 3-6 mm in each of four tests. It should be noted that all of these
anchorage displacements were measured post-test and the maximum dynamic
displacement during the test may potentially have been larger.
The anchorage displacements in the Dorel tests are shown in Table 57.
Table 57: Anchorage displacement in the Dorel – forward and rearward facing
integral CRSs
CRS
Low rating
Cosmo
Low rating
Cosmo
Low rating
Cosmo
Low rating
Babymax
Low rating
Babymax
Low rating
Babymax
Dummy
Final
anchorage
disp.
(mm)
Maximum
anchorage
disp.
(mm)
Q1
95
Q1
89
Q1
90
Q1.5
95
195
Q1.5
18
190
Q1.5
146
145
Mean
Comment
Intrusion in contact with CRS for
duration of the test
91
CRS lost contact with intrusion.
ISOFix anchorages hit the stops &
rebounded
177
CRS lost contact with intrusion. CRS
stopped and rebounded
CRS lost contact with intrusion. CRS
stopped and rebounded
In the Dorel tests, the rear facing integral CRSs remained in contact with the intrusion
panel throughout the test, although the anchorage displacement was considerably
greater than in the TRL tests (89-95 mm in the Dorel tests, compared with 36-62 mm in
the TRL tests). This represents a considerable difference in the effective door intrusion
between the Dorel and TRL tests on the same CRS, due to differences in the lower
anchorage performance.
The three forward facing integral CRSs in the Dorel tests had very different anchorage
displacements. All three seats lost contact with the intrusion panel after approximately
95 mm of displacement, after which the responses varied considerably:
TRL
•
The first seat hit the stops at the end of the lower anchorage bar and rebounded
100 mm;
•
The second seat stopped approximately 5 mm before hitting the stops (it
apparently jammed on the lower anchorage bar) and rebounded 172 mm;
•
The third seat stopped approximately 5 mm before hitting the stops (it apparently
jammed on the lower anchorage bar) and did not rebound.
140
CPR821
These results are very different to the anchorage displacement range of 42-52 mm in the
TRL tests with the same CRS model. This shows a considerable difference in the
constraint of the lower anchorages between the TRL and the Dorel tests with this forward
facing CRS. The Dorel results also show poor repeatability of the lower anchorage
performance for nominally identical CRSs on a single bench.
These results may explain why the neck and pelvis measurements were generally much
greater in the TRL reproducibility tests than in the Dorel reproducibility tests. At the very
least, these results strongly suggest that the anchorage displacement should be
controlled to ensure consistent loading of the CRS and good reproducibility of the test
conditions.
Reg.14 states that the minimum width of each ISOFix lower anchorage is 25 mm, and
Reg.44 states that the width of the CRS ISOFix attachment must not exceed 25 mm, but
in practice some designs are as narrow as 5 mm. If the lower ISOFix attachment is
designed to meet the minimum width, the maximum lateral translation of the CRS
attachment in an impact is 25 mm minus the width of the CRS anchorage, i.e. the
maximum translation could range from zero to approximately 20 mm. There is no upper
limit on the width of the ISOFix lower anchorage, so in theory the attachment
displacement could be much greater than 20 mm. However, in practice this is limited by
the seat foam and underlying seat structure. In particular, for front seats or individual
rear seats, the displacement of the in-board attachment will be limited by the width of
the seat and the seat structure and is unlikely to achieve the displacements seen in the
side impact testing. It is possible that the out-board anchorage (nearest the door) could
displace as the vehicle seat is crushed, however it is unlikely that the inboard anchorage
is likely to displace substantially, thus limiting the displacement of the lower outer
anchorage by the amount that the CRS is crushed in the impact.
Furthermore, it may be difficult to design a large, yet well-controlled displacement (i.e.
with consistent friction levels between different sleds), and relatively easy to specify a
small displacement with a hard stop, at least for the out-board anchorage, such as may
be found in front or individual rear seats.
The results of these tests suggest that many of the anchorage displacements observed in
these tests were excessive, at least for representing front seats or individual rear seats.
It is recommended that consideration be given to limiting, and possibly eliminating,
anchorage displacement in the tests in order to better represent front and rear individual
seats, and the worst case for rear bench seats. Whether ISOFix anchorages move to the
extent that an ISOFix CRS will translate to the degree observed in these tests is
questionable and needs to be verified.
Section A.7.3 noted that the real-world accident analysis found that the largest
proportion of side impacts occur of at 60°, followed by 90°, and that the risk of fatality is
significantly greater in a 90° impact. The results of the testing indicated that the ISOFix
anchorage sometimes jammed (limiting the lateral displacement of the anchorage), even
though the door impact in the tests is at 90°. Limited (or eliminated) anchorage
displacement would be more realistic of the real-world loading on the CRS.
C.6.4.4 Intrusion
The real-world accident analysis in Section Appendix A (see Figure 26) showed that
injury increased with increasing intrusion (and that this was the most important factor
affecting injury outcome). However, the reproducibility results (see Section C.6.5.2 show
TRL
141
CPR821
either no influence of intrusion, or a reduction of injury measures with increasing
intrusion - which is opposite to the real-world observation.
The position of the CRS on the test bench was defined during ISO investigations and was
determined by measuring the distance from the inner door trim to the centre of a CRS in
a number of vehicles. This may mean that, to do well in the test procedure, it may be
better to have a narrow CRS (door will impact it later, when the sled is slower, but there
is less room for padding). Or it may be better to have a wider CRS (will get impacted
when the sled is moving faster, but has more space for padding to absorb the impact).
Defining the initial door position relative to the bench (see Section B.4.4) may encourage
the former, which could then perform much worse in a narrower car. The effect of CRS
positioning with fixed anchorages should be investigated, so that the set-up represents
the worst case scenario and CRSs cannot perform artificially well.
The displacement of the CRS anchorages was variable. There was no obvious
relationship between the initial distance between the intrusion panel and the CRS, and
the displacement of the anchorages, in the TRL tests (see Figure 74).
70
Anchorage displacement (mm)
60
50
40
30
Linear trendline
20
10
0
150
170
190
210
230
250
Initial distance between door and CRS (mm)
Figure 74: Anchorage displacement vs. initial distance between the door and
the CRS in the TRL test series
TRL
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CPR821
C.6.5 Repeatability and reproducibility
Table 58 shows the sub-set of tests for which repeat tests were performed at TRL and at
Dorel to assess repeatability of the test procedure. The forward and rearward facing
integral CRSs were tested at both facilities to allow assessment of the reproducibility of
the test procedure.
Table 58: Test matrix for the assessment of repeatability and reproducibility
ATD
No. of Tests
Q1.5
3
Q1
3
Q6
3
Q1.5
3
Q1
3
Tests at TRL
Group 0+ low rating
Babymax
Group I low rating
Cosmo
Group II low rating
Monte Carlo
Tests at Dorel
Group 0+ low rating
Babymax
Group I low rating
Cosmo
C.6.5.1 Repeatability
The repeatability results from the TRL tests are shown in Table 59 and for the Dorel tests
in Table 60. The limits proposed by the Informal Working Group are also shown,
although it should be noted that these are front impact limits (see Section C.6.6 for a
discussion of the use of these limits in side impact).
procedures (see e.g. ISO 15830 Part 1). The CV’s from the TRL tests are generally well
within the acceptable range, except for the negative upper neck extension moment in
the Q1.5 tests, and the positive upper neck extension moment in the Q6 test. For the
Q1.5, the negative neck extension moment measurements were very small compared
with the proposed limit (mean -8.9 Nm c.f. a limit of -61 Nm). For neck extension
moment measurements near the limit, the same absolute variation in measurements
would give a much lower CV; however, it cannot be guaranteed that the absolute
variation would not increase with increasing measurements. Nevertheless, given that the
measurements were very much smaller than the limits suggested by the Informal
Working Group, the variability is not expected to be a problem within the test procedure.
The same may be said of the positive neck extension moment in the tests with the Q6
dummy.
For the Dorel tests, all the dummy measurements showed good or acceptable CV except
the chest resultant acceleration for the Q1 test, which had a CV slightly greater than
TRL
143
CPR821
10%. In this case, the mean measurement was greater than the limit proposed by the
Informal Working Group.
In the discussion of the sled pulses in Section C.6.3 it was noted that the last part of the
acceleration pulse on the TRL sled was somewhat inconsistent and that this may affect
the repeatability of the head acceleration metrics. However, Table 59 shows that the
repeatability of the peak resultant head acceleration and HIC were both very good, with
a maximum CV of 4.2 for the two metrics across the three seats that were tested. This
compares favourably with a maximum CV of 6.5 for HIC in the Dorel tests, even though
the sled acceleration was more consistent during peak head resutlant acceleration in the
Dorel tests.
TRL
144
CPR821
Table 59: Repeatability results from the TRL sled tests
TRL Side Impact
Head
resultant
accel (g)
Rearward
Facing
Integral
Q1.5
Limits
76
Mean
SD
CV
105.5
2.4
2.3%
Forward
Facing
Integral
Q1
Limits
72
Mean
SD
CV
66.7
2.53
3.8%
Forward
Facing nonintegral
Q6
Limits
89
Mean
SD
CV
54.7
1.00
1.8%
TRL
HIC15
578741
750
28.1
3.7%
491629
423.8
17.6
4.2%
10831389
267.8
4.66
1.7%
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
1364
61
-61
38
55
1186
38.4
3.2%
20.5
0.62
3.0%
-8.9
1.72
-19.4%
19.3
1.13
5.9%
66.5
6.37
9.6%
1201
53
-53
40
55
710
46.85
7.0%
6.3
0.35
5.5%
-13.8
0.55
-4.0%
18.9
1.19
6.3%
60.5
1.25
2.1%
106
2.74
2.6%
2304
118
-118
33
55
-
1517
48.73
3.2%
14.8
1.65
11.1%
-15.3
0.23
-1.5%
15.1
1.23
8.2%
48.5
2.22
4.6%
72.8
2.30
3.2%
145
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
90.0
2.11
2.3%
CPR821
Table 60: Repeatability results from the Dorel sled tests
Dorel Side Impact
TRL
Head
resultant
accel (g)
Rearward
Facing
Integral
Q1.5
Limits
76
Mean
SD
CV
105.6
4.35
4.1%
Forward
Facing
Integral
Q1
Limits
72
Mean
SD
CV
66.2
1.11
1.7%
HIC15
578741
795
51.82
6.5%
491629
414
14.60
3.5%
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
1364
61
-61
38
55
847
37.83
4.5%
18.6
1.69
9.1%
-9.37
0.64
-6.9%
N/A
N/A
N/A
71.8
6.02
8.4%
1201
53
-53
40
55
611
51.69
8.0%
5.4
0.36
6.7%
-11.13
0.78
-7.0%
N/A
N/A
N/A
67.8
6.88
10.1%
146
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
73.6
1.62
2.2%
113.6
7.07
6.2%
CPR821
C.6.5.2 Reproducibility
The reproducibility of the test procedure was evaluated with two sets of three tests at
TRL and Dorel. The reproducibility results for the forward facing CRS and the Q1 dummy
are shown in Table 61 and for the rearward facing CRS and Q1.5 dummy are shown in
Table 62. These results represent the combined variation due to the sled, sled
deceleration method, intrusion profile, dummies and restraints, however TRL supervised
test set-up in both labs to keep it relatively consistent.
ISO define good reproducibility as a CV lower than 10%, for all dummy performance
criteria in certification and other test procedures (see e.g. ISO 15830 Part 1). A number
of the dummy measurements in these tests at two laboratories exceed this guideline.
Most of the neck loads have a reproducibility CV exceeding 10% and in four of these five
cases the measurements in the TRL tests were much larger than the measurements in
the Dorel tests. Different dummies and test benches were used at two different test
laboratories, with different deceleration systems (crush tubes at TRL and a hydraulic
system at Dorel). Furthermore, the intrusion profiles were different in the two test
configurations, with 100 mm greater intrusion in the Dorel tests compared with the TRL
tests (see Section B.4.4).
Even though there was 100 mm less intrusion in the TRL configuration than the Dorel
configuration, the peak values for the neck forces and moments in the forward facing
seat, and the pelvis acceleration in the rearward facing seat, were generally much higher
in the TRL tests. It was observed that the CRS typically moved away from the intrusion
panel relatively easily in the Dorel tests, but was driven sideways in the TRL tests.
Table 61: Reproducibility results for the sled tests with the Q1 dummy in a
forward facing CRS
Mean
SD
CV
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
66.5
1.77
2.7%
419
15.37
3.7%
661
69.84
11%
+ve Upper
neck Mx
(Nm)
-ve Upper
neck Mx
(Nm)
5.9
0.61
10.3%
-12.5
1.57
-12.6%
Chest
resultant
accel (g)
64.2
5.98
9.3%
Pelvis
resultant
accel (g)
109.6
6.47
5.9%
Table 62: Reproducibility results for the sled tests with the Q1.5 dummy in a
rearward facing CRS
Head
resultant
accel (g)
Mean
SD
CV
105.5
3.15
3.0%
HIC15
Upper
neck Fz
(N)
+ve Upper
neck Mx
(Nm)
-ve Upper
neck Mx
(Nm)
772
44.76
5.8%
1016
189.06
18.6%
19.5
1.54
7.9%
-9.1
1.20
-13.1%
Chest
resultant
accel (g)
69.2
6.26
9.0%
Pelvis
resultant
accel (g)
81.8
9.14
11.2%
C.6.6 Evaluation of proposed dummy performance criteria
The test matrix for the evaluation of dummy performance criteria for rearward facing
CRSs is shown in Table 63, and the dummy measurements for all of the rearward facing
CRSs tests are shown in Table 64.
TRL
147
CPR821
Table 63: Test matrix for criteria evaluation - rearward facing integral CRSs
Lab
TRL
TRL
TRL
TRL
TRL
Dorel
Systems
ATD
No. of
Tests
Q1.5
3
Q0
1
Q1
1
Q1.5
1
Q1.5
1
Q1.5
1
High volume 3, Cabriofix belted
Q1.5
1
Low rating, Babymax
Q1.5
3
Low rating , Babymax
High rating, Babysafe
High volume 1, Cabriofix
High rating, Modified Babysafe
(degraded)
Evaluation of criteria - Rearward facing integral CRSs
was contained in all cases and neck forces and moments all pass, which is likely to be
due to head containment. Containment of the head will help minimise the neck loads.
However the resultant head acceleration limit was exceeded in all tests. Only one CRS
was within the lower HIC limit and six were within the upper HIC limit and five exceeded
the upper limit. These results suggest that either the limits are too low or that CRSs
need to be improved to provide more energy absorption in a lateral impact. The accident
studies suggested that the head is an area that needs to be better protected in lateral
impacts and therefore the injury criteria need to be set at a level that will improve CRS
design. If these criteria are applied to the side impact test procedure it is likely to lead to
CRSs that absorb the loading more effectively in lateral impacts.
Chest, abdomen and neck injuries have been shown to vary in importance between
different accident studies. However, chest and abdomen account for a significant
proportion of AIS 3+ injuries to children in side impact. These injuries have been found
to be caused by compression of the child by the door panel of the vehicle. The chest
compressions all passed the limits but the resultant chest accelerations all failed. Again,
this may suggest that either the limits have been set too low or that CRSs need to
improve the way they provide protection to a child’s chest in a lateral impact. If these
chest criteria are applied to the side impact test procedure it is likely to lead to CRSs
that absorb the loading more effectively in the chest area.
There are no limits on pelvis acceleration, as the pelvis region hasn’t been shown to be a
priority body region to protect in the accident review. However the pelvis values seem
quite high compared with e.g. WorldSID data for defining injury thresholds.
TRL
148
CPR821
Table 64: Test results for criteria evaluation - rearward facing integral CRSs1
Group 0+ CRSs
Dummy
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Q0 front impact limits
85
523-671
546
17
-17
High rating
Babysafe
Q0
108
704
211
4
3
N/A
66
72
491-629
1201
53
-53
40
55
High rating
Babysafe
81
541
692
17
6
18
59
76
578-741
1364
61
-61
38
55
Q1
Q1.5 front impact limits
TRL
Chest
compression
(mm)
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
55
84
91
Low rating
Babymax2
Q1.5
109
818
815
18
10
N/A
70
72
Low rating
Babymax2
Q1.5
107
831
836
21
9
N/A
79
74
Low rating
Babymax2
Q1.5
101
735
889
17
10
N/A
67
75
Low rating
Babymax
Q1.5
108
782
1159
20
9
20
61
91
Low rating
Babymax
Q1.5
104
736
1230
21
11
20
65
91
Low rating
Babymax
Q1.5
104
731
1169
21
7
18
73
88
High rating
Babysafe
Q1.5
83
565
864
21
7
22
66
81
149
CPR821
Group 0+ CRSs
Dummy
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
High rating
Babysafe
(degraded)3
Q1.5
98
716
782
20
11
26
64
110
High volume
sales Cabriofix
Q1.5
98
715
865
22
5
20
71
72
High volume
sales 3 Cabriofix
(belted)
Q1.5
119
990
586
23
8
21
61
67
1
The head was contained in all tests
2
Tests performed by Dorel, no chest compression instrumentation fitted
3
For this test, the Babysafe seat was modified by taking out the energy absorbing liner and cutting away the side wing
TRL
150
CPR821
The test matrix for the evaluation of dummy performance criteria for forward facing
CRSs is shown in Table 65, and the dummy measurements for all of the forward facing
CRS tests are shown in Table 66.
Table 65: Test matrix for criteria evaluation - forward facing CRSs
Lab
ATD
No. of
Tests
TRL
Group I low rating, Cosmo
Q1
3
Q1
1
TRL
Group I high rating, Priorifix
Q3
1
Q1
1
Q3
1
Q1
1
Q3
1
TRL
TRL
Group I high volume, Iseos
Group I high volume 2, Duo
TRL
Group II low rating, Monte Carlo
Q6
3
Group II high rating, Solution Xfix
Q3
1
TRL
Q6
1
Q3
1
Q6
1
Q1
3
TRL
Dorel
Group II high volume, Kidfix
Group I low rating, Cosmo
Evaluation of criteria - Forward facing CRSs
For all children injured in side impact protecting the head is the main priority. Injuries to
was contained in all cases and neck forces and moments all pass, which is likely to be
due to head containment. As mentioned earlier, containment of the head will help
minimise the neck loads. The resultant head acceleration limit was exceeded in 5 out of
19 tests and 4 of these exceeded the lower HIC limit. These results suggest that it is
possible to design CRSs that pass the criteria and that, considering head protection is an
area that needs improving, if the criteria were set at this level, it would lead to an
improvement in CRSs design.
The chest is an area that has been identified as a priority to protect. The chest
compressions all passed the criteria, however 12 out of 19 CRSs exceeded the limit for
resultant chest acceleration. Again, this may suggest that either the limits have been set
too low or that CRSs need to improve the way they provide protection to a child’s chest
in a lateral impact. If these chest criteria are applied to the side impact test procedure it
is likely to lead to CRSs that absorb the loading more effectively in the chest area.
There are no limits on pelvis acceleration, as the pelvis region hasn’t been shown to be a
priority body region to protect in the accident review. However the pelvis values seem
quite high particularly for the Q1 tests.
TRL
151
CPR821
Table 66: Test results for criteria evaluation - forward facing CRSs1
CRS
Dummy
TRL
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
Chest
resultant
accel (g)
72
491-629
1201
53
-53
40
55
Pelvis
resultant
accel (g)
Group I Low
rating Cosmo2
Q1
66.4
418
630
6
-11
N/A
65.8
119.8
Group I Low
rating Cosmo2
Q1
67.2
427
553
5
-12
N/A
75.5
105.9
Group I Low
rating Cosmo2
Q1
65
398
651
5
-11
N/A
62.2
115.1
Group I Low
rating Cosmo
Q1
69.2
440
763
6
-13
19.7
59. 9
106.1
Group I Low
rating Cosmo
Q1
64.2
405
673
7
-14
17.5
61.9
102.7
Group I Low
rating Cosmo
Q1
66.7
427
694
6
-14
19.4
59.6
108.1
Group I High
rating Priorifix
Q1
92.3
642
859
6
-20
18.0
66.1
102.1
Group I High
volume sales
Iseos
Q1
87.3
594
784
7
-18
20.5
73.9
119.0
Group I High
volume sales 2
Duo
Q1
84.1
521
631
9
-20
18.2
62.2
108.4
152
CPR821
CRS
Dummy
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
81
7801000
1705
79
-79
36
55
-
Group I High
rating Priorifix
Q3
64.9
384
1182
8
-21
21.1
51.6
88.9
Group I High
volume sales
Iseos
Q3
63.4
371
943
12
-20
23.0
63.5
94.9
Group I High
volume sales 2
Duo
Q3
55.8
422
837
9
-25
22.0
57.0
72.2
Group II High
rating Solution
X-fix
Q3
75
449
1474
7
-13
16.3
55.0
85.7
Group II High
volume sales
Kidfix
Q3
90.2
591
1169
7
-13
16.1
82.1
95.9
89
10831389
2304
118
-118
33
55
-
Group II Low
rating Monte
Carlo
Q6
54.8
264
1462
16
-15
14.2
46.9
73.1
Group II Low
rating
Q6
53.6
266
1555
13
-16
14.5
47.6
70.4
Q6
55.6
273
1535
16
-15
16.5
51.0
74.9
Monte Carlo
Group II Low
rating
Monte Carlo
TRL
153
CPR821
CRS
Dummy
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
Chest
resultant
accel (g)
Pelvis
resultant
accel (g)
Group II High
rating Solution
X-fix
Q6
63.1
332
1543
5
-14
9.6
47.4
78.7
Group II High
volume sales
Kidfix
Q6
65.7
364
1485
11
-14
18.0
59.3
81.0
1
Head contained in all tests
2
Tests performed by Dorel, no chest compression instrumentation fitted
TRL
154
CPR821
C.6.7 The effect of varying friction in the ISOFix anchorages
The ISOFix anchorages are allowed to move laterally in the proposed test procedure. It
is unlikely that the ISOFix anchorages would move in this way in the vehicle. TRL carried
out 3 exploratory tests to indicate what the effects of increasing the friction of the ISOFix
anchorages may be. The test matrix for this small study is shown in Table 67.
Table 67: TRL Test matrix for investigation into the effects of increased friction
on the lateral movement of ISOFix anchorages
Integral CRSs
ATD
No. of Tests
Group 0+ low rating, Babymax
Q1.5
3
Group 0+ low rating, Babymax
Q1.5 increased
friction
1
Group I low rating , Cosmo
Q1
3
Group I low rating , Cosmo
Q1 increased friction
1
Group I high rating , Priorifix
Q3
1
Group I high rating , Priorifix
Q3 increased friction
1
The differences that were seen were not large. The friction was increased from 8-10N to
80-90N. Although no statistical assessment can be made some differences were seen,
taking into consideration the repeatability of the relevant body regions:
•
The upper neck tension and resultant pelvis acceleration were higher with low
friction in the tests with the Q1.5 dummy.
• The resultant head acceleration and HIC were slightly higher with low friction in
the tests with the Q1 dummy.
• The HIC, chest compression and resultant pelvis acceleration were lower with low
friction in the tests with the Q3 dummy
The results indicate that the amount of friction allowed in the ISOFix anchorages would
have an effect on the test procedure. With the friction applied in these tests, the ISOFix
anchorages were still able to move relatively freely in the test. It is recommended that
further investigation is carried out to allow the set-up procedure to be more
representative of the CRS when attached to anchorages in the vehicle.
TRL
155
CPR821
Table 68: Test results for evaluation of the effect of friction1, 2
CRS
Dummy
Head
resultant
accel (g)
HIC15
Upper
neck Fz
(N)
+ve upper
neck Mx
(Nm)
-ve upper
neck Mx
(Nm)
Chest
compression
(mm)
Chest
resultant
accel (g)
Limits
Q1.5
76
578- 741
1364
61
-61
38
55
Group 0+ low
rating Babymax
Q1.5
108
782
1159
20
-9
20
61
91
Group 0+ low
rating Babymax
Q1.5
104
736
1230
21
-11
20
65
91
Group 0+ low
rating Babymax
Q1.5
104
731
1169
21
-7
18
73
88
105
750
1186
21
-9
19
66
90
76
Mean
Group 0+ low
rating Babymax
(increased
friction)
Q1.5
104
748
1078
20
-9
17
63
Limits
Q1
72
491- 629
1201
53
-53
40
55
Group I low
rating Cosmo
Q1
69
440
763
6
-13
20
60
106
Group I low
rating Cosmo
Q1
64
405
673
7
-14
17
62
103
Group I low
rating Cosmo
Q1
67
427
694
6
-14
19
60
108
67
424
710
6
-14
19
61
106
Mean
TRL
Pelvis
resultant
accel (g)
156
CPR821
Group I low
rating Cosmo
(increased
friction)
Q1
63
393
706
5
-13
21
61
108
Limits
Q3
81
780-1000
1705
79
-79
36
55
-
Group I high
rating Priorifix
Q3
65
384
1182
8
-21
21
52
89
Group I high
rating Priorifix
(increased
friction)
Q3
62
364
1250
8
-19
26
54
97
1
The head was contained in all tests
2
Yellow highlights show where the standard friction results were notably different to the increased friction results
TRL
157
CPR821
Appendix D
Testing observations and possible restraint
regulation non-conformities
During the course of the dynamic testing on the child restraints, several nonconformities with the regulation were observed.
D.1 Rearward facing integral restraints
D.1.1 Low rated restraint – IWH Babymax
•
The ISOFix anchorages had to be moved forward in x-axis to 40mm from CR
point in the front and rear impact tests to allow attachment of the base. However
this was not required when attaching it to the Reg.44 test bench. This may mean
there could be a compatibility issue with vehicle in the current fleet, causing a
problem if this CRS was approved as “universal” under the new regulation (as
there would not be a vehicle application list).
•
The stiffness of new regulation cushion and design of restraint base (metal cross
bar between anchorages) meant that the carrier had to be attached to the base
and then the base was attached to ISOFix anchorages. This means the CRS could
not be installed as described by the instructions.
•
The Regulation 44 approval label was included as an image in the instruction
markings on the side of the restraint.
•
The approval label image was only for a universal CRS and did not include a
second semi-universal approval label for use when installed using the ISOFix
base.
•
The instruction markings/approval label was missing on several of the tested
CRSs. This is not allowed under the current Reg.44.
•
There was no approval label on any of the ISOFix bases. This means that a
consumer would be using the restraint illegally, as it does not appear to have a
Reg.44 approval.
•
The CRS shell cracked in one of the side impact tests.
D.1.2 High sales restraint – Maxi-Cosi Cabriofix
•
The stiffness of new regulation cushion did not allow base to ratchet into
anchorages (when force specified by the regulation 135±15N is applied), however
it did connect to the anchorages correctly.
D.2 Forward facing integral restraints
D.2.1 Low rated restraint – Nania Cosmo
TRL
•
The top tether clip was over 12mm wide, outside of the design requirements
specified by Reg.44.
•
On several of the products the top tether strap contained a twist which was
removed before testing.
158
CPR821
•
The sticker was incorrectly placed on some ISOFIX anchorages so that it still
showed part red when connected correctly. This is contrary to the requirements
of Reg.44.
•
The Regulation 44 approval label was included as an image in the instruction
markings on the side of the restraint.
•
It was quite easy to peel the instruction markings off the product.
•
The ISOFix anchorages deformed, but did not detach, during the side impact tests
and the restraint was difficult to remove from test bench in two of the tests.
D.2.2 High rated restraint – Maxi-Cosi Priorifix
•
The instruction markings were peeling off on one seat prior to test.
D.2.3 High sales restraint – Bebe Confort Iseos
•
The top tether indicator indicated green at around 15N, during the setup of the
Q1 test. This means the tether will appear to the consumer to be suitably
tightened, when actually it could be significantly tighter, therefore improving the
dynamic performance of the CRS.
•
The adjuster strap appeared to slip through the adjuster by 2mm in the Q3 test.
D.3 Forward facing non-integral restraints
D.3.1 Low rated restraint – Jane Monte Carlo
•
The ISOFix anchorages had to be moved forward in x-axis to 55mm from CR
point in the front impact tests to allow attachment of the restraint. This may
mean there could be a compatibility issue with vehicle in the current fleet,
causing a problem if this CRS was approved as “universal” under the new
regulation (as there would not be a vehicle application list).
•
The adjustable head pad split on right hand-side during the front impact with the
Q3.
•
The adjustable head pad split on both sides during the front impact with the Q6.
This meant the belt guide was no longer attached to the main part of the
restraint. This would be a fail of the current Reg.44 dynamic testing requirements
(7.1.4.1.8).
D.4 Side impact
TRL
•
The seat back cushion had torn at the “T” join on the impact side
•
The belt anchorages limit the ISOFix displacement, which may or may not be
representative.
159
CPR821
Appendix E
Review of the Implementation Phasing of
the new Regulation
E.1 Introduction
It has been proposed by the Informal Group that the new regulation should be
introduced in three phases to expedite its progress:
•
Integral i -Size ISOFix CRSs
•
Integral and non-integral i -Size ISOFix CRSs
•
All CRSs
In addition to the above, there are potentially two approval routes that could be
followed:
•
Approval of a CRS to either Reg.44 or the new regulation (single approval)
•
Approval of a CRS to Reg.44 and the new regulation simultaneously (dual
approval).
This phased introduction may have a number of potential effects and the interactions
between the phasing and the approval routes may have implications for consumers and
for manufacturers, and these are discussed in the following sections.
E.2 Definitions
It is proposed by the Informal Group that the implementation of the new Regulation be
split into three phases, each incorporating different types of restraints. At this stage,
how long each phase will last has not been defined. However, CRS models are estimated
to last at least a minimum of 3 years. The restraint type categories for Reg.44 and the
proposed new Regulation are shown in Table 69, and the terms used are explained in
Table 70. The phases are described in Section E.3.
Table 69: Restraint type categories
Restraint
type
New
regulation
categories
Belted-only
integral
or
non-integral
universal
integral
universal or
semiuniversal or
specific
vehicle
integral
universal or
semiuniversal or
specific
vehicle
ISOFixintegral
ISOFix or
Belted,
integral
ISOFix-non
integral
TRL
non-integral
Reg.44
categories
semiuniversal
New
regulation
sizing
?
Defined by
height
range and
Child +
CRS • [33
kg]
Defined by
height
range and
Child +
CRS • [33
kg]
Defined by
height
range and
Child +
CRS • [33
kg]
160
Reg.44
mass
Groups
Group 0+
Group I
Group
II/III
Description
Restraints (with or without
an integral restraint),
installed using only the
adult seat-belt
Group 0+
Group I
ISOFix-only seats with an
integral restraint (no seatbelt attachment)
Group 0+
Group I
CRSs can be installed
using the seat-belt or
ISOFix attachments; in
both cases the occupant
has an integral restraint
Group
II/III
Non-integral CRSs
installed using the seatbelt, but with additional
anchorages attaching to
the ISOFix anchorages
CPR821
Table 70: Definitions
Term
Explanation
ISOFix
The CRS is installed in a vehicle using the ISOFix anchorages located in
a vehicle, defined in Reg.14
Belted
The CRS is installed in a vehicle using the vehicle seat-belt
Integral
The CRS has an integral restraint as the primary means of holding the
occupant in the CRS,
Non-integral
The CRS uses a method external to the CRS as the primary means of
restraining the occupant, e.g. seat-belt
Universal
For Reg.44, the CRS is able to be installed in most positions in the
vehicle. For Reg.44 ISOFix the CRS has a top tether anti-rotation
device.
Semi-universal
Examples of semi-universal CRSs:
Specific vehicle
Anti-rotation device
Reception area
•
Forward facing restraints equipped with support leg
•
Rearward facing restraints equipped with a support leg or a top
tether strap
•
Rearward facing restraints, supported by the vehicle dashboard,
for use in the front passenger seat
•
Lateral facing position restraint equipped if needed with an antirotation device
A CRS that can only be used with specific vehicle types
This is a device intended to limit the rotation of the child restraint
system during an impact consisting of either:
•
A top-tether strap fitted top tether anchorages (defined in Reg.14)
•
A support leg contacting the vehicle floor area (to be defined in
Reg.14)
This will be a defined volume representing the possible placement
positions, of a support leg onto a vehicle floor. This will be defined in
Reg.14 and 16.
E.3 Implementation phases
E.3.1 Phase 1
The first implementation phase will only introduce ISOFix integral CRSs into the new
Regulation. This includes the current Reg.44 Group 0+ and Reg.44 Group I CRSs with
integral restraint, whether universal, semi-universal or for a specific vehicle. However, to
introduce these as “universal” (which requires the CRS to have an anti-rotation device)
will mean an alternative 3rd attachment point needs to be defined for CRSs which have a
support leg. The proposed first implementation phase of the new Regulation is shown in
Figure 75: the first column shows the Reg.44 categories that will remain in force during
the first phase, and the second column shows the new Regulation categories that will be
introduced to exist in parallel with Reg.44.
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Phase 1
Reg.44
Approval
new Regulation
Approval
Belted only
ISOFix integral
ISOFix or Belted,
integral
ISOFix non-integral
ISOFix integral
Figure 75 – new Regulation implementation Phase 1
E.3.2 Phase 2
The second implementation phase will introduce CRSs that primarily restrain the
occupant using the vehicle seat-belt, but which have additional anchorages that also
attach to the ISOFix anchorages in the vehicle. These CRSs are typically booster systems
(Reg.44 Group II/III). However, to introduce these as “universal” requires the location of
the ISOFix and belt anchorages in the vehicles to be aligned so that the restraints can be
installed correctly. Integral ISOFix-only and ISOFix non-integral CRSs, will no longer be
able to be approved to Reg.44. Figure 76 summarises the implementation for phase 2.
Phase 2
Reg.44
Approval
new Regulation
Approval
Belted only
ISOFix or Belted,
integral
ISOFix integral
ISOFix non-integral
E.3.3 Phase 3
The final implementation phase will incorporate the remaining restraints and will mean
that Regulation 44 is no longer used. This means all restraints that are installed using
the vehicle seat-belt, and restraints which have the option to use either ISOFix or seatbelt installation will be included into the new Regulation, along with integral and nonintegral ISOFix CRSs. Figure 77 summarises the implementation for phase 3.
Phase 3
Reg.44
Approval
new Regulation
Approval
None
Belted only
ISOFix integral
ISOFix or Belted,
integral
ISOFix non-integral
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E.4 Approval routes
There are several different implications for manufacturers and consumers depending on
whether CRSs are allowed to have only a single approval, to Reg.44 or the new
Regulation, or a dual approval to both Regulations simultaneously.
For example, if dual approval was possible, during phase 1 an ISOFix-only integral CRS
could be approved to the Reg.44 regulation as well as the new Regulation. If only a
single approval is possible, the manufacturer would have to choose which of the two
regulations to approve the CRS to.
E.4.1 Single approval
With the single approval option, a CRS could only be approved to one of the regulations.
Figure 78 shows the different approval options for each type of CRS, during each
implementation phase of the new Regulation, and these options are discussed in more
detail in the following sections.
E.4.1.1 Phase 1
Belt-attached integral and non-integral CRSs
All belt-attached integral and non-integral CRSs will remain approved to Reg.44 under
Phase 1.
ISOFix-only integral CRSs
Manufacturers would have the choice whether they wish to approve their CRSs to the
new Regulation or Reg.44 during Phase 1. After Phase 1, manufacturers would only be
able to approve these CRSs to the new Regulation and therefore for products with a long
life-span, approving to the new Regulation would be beneficial. However, there will most
likely be a phasing-out process, allowing CRSs already approved to Reg.44 time to
switch to the new Regulation before they can no longer be sold.
Currently, the number of ISOFix-only CRSs is low, and therefore the number of CRSs
affected by this Phase may be small. However as the new Regulation aims to improve
CRS design by introducing more stringent assessment criteria, CRSs that have the option
of being attached with the adult belt may be phased out and replaced by CRSs
specifically designed as ISOFix-only.
Initially there may also be an attraction for some manufacturers to approve their
products to the new Regulation to exploit the marketing value it may bring. However,
manufacturers of CRSs with lower performance and low-cost/high-volume sales may
avoid approving to the new Regulation until it is compulsory.
ISOFix-or-belt-attached integral CRSs
Implementation of Phase 1 of the new Regulation will mean that CRSs that can be
installed using either ISOFix or the seat-belt will continue to be approved to Reg.44.
These CRSs are currently the most common type of ISOFix restraints in the market
place. This type of CRS typically contains the belt guides on the CRS itself (Group I), or
have a separate base for ISOFix attachment (typically infant carriers). Excluding this
type of restraint from Phase 1 could lead to a two-tiered ISOFix structure. The ISOFixonly CRSs may be dynamically better performers (due to the stricter approval
requirements), but not as desirable to the consumer, as they are constrained to only
fitting into vehicles with ISOFix anchorages and not able to be fitted into a second
vehicle using the seat-belt. Vehicle manufacturers will also have to indicate which size of
CRSs and which regulation their vehicle seating positions are compatible with.
ISOFix non-integral CRSs
ISOFix non-integral CRSs will continue to be approved to Reg.44 under Phase 1.
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E.4.1.2 Phase 2
Phase 2.
ISOFix integral CRSs
All ISOFix integral CRSs will be approved to the new Regulation.
These child restraints will still have to be approved to Reg.44. This again could lead to a
two-tier ISOFix performance in the market place. It could also lead to a slow take-up of
the new regulation if the majority of CRSs continue to be designed so that they can also
be attached using the seat-belt. These systems may be preferred by the consumer for
the flexibility to use it in a second vehicle. However, it could be argued that by the time
this phase is introduced, compulsory ISOFix in vehicles will have been around for
sufficient time (since 2006 for new vehicles) that the large majority of the vehicle fleet
will have ISOFix anchorages.
These CRSs will only be able to be approved to the new Regulation. These CRSs are
currently approved as “semi-universal” in Reg.44. However, in the new Regulation the
idea is for them to be “universal”, thus not requiring a vehicle application list. For this to
occur, the seat-belt anchorages and the ISOFix anchorages will need to be aligned in the
vehicle, to avoid poor fitment of the seat-belt across the occupant. Currently, there are
vehicles where the ISOFix anchorages are offset from the seat-belt anchorages.
Some products may have compatibility issues with the new Regulation and thus the
manufacturers may choose to maintain approval to Reg.44 until it is phased out. This
does not encourage design improvement. However, it is thought that new products will
be designed to meet the requirements of the new Regulation.
E.4.1.3 Phase 3
All remaining CRS types will be approved to the new Regulation, and Reg.44 will cease
to exist. However, it may be very challenging for belt-attached CRSs to gain type
approval to the increased performance requirements proposed in the new regulation.
E.4.2 Dual approval
With this option a CRS could be approved to either one of the Regulations or both. Figure
79 shows the different approval options for each type of CRS, during each
implementation phase of the new Regulation.
E.4.2.1 Phase 1
phase 1.
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CRS manufacturers would have the choice to approve their CRSs to the new Regulation,
to Reg.44, or to both Regulations during Phase 1. As previously mentioned, the number
of ISOFix integral CRSs in the market is currently low and it is therefore unclear, during
phase 1, how many of these restraints will be approved to the new Regulation.
Manufacturers may see an attraction from the marketing value it may bring. However,
manufacturers of CRSs with lower performance and low-cost/high-volume sales may
avoid approving to the new Regulation until it is compulsory.
Whether there will be a benefit for manufacturers to approve new products to both
regulations is unclear. It is likely that manufacturers’ of existing CRSs, already with a
Reg.44 approval, may also have the CRSs approved to the new Regulation.
Manufacturers of new restraint designs may not see the cost-benefit of approving their
product to two regulations and therefore may choose only to approve the restraint to the
new Regulation. Products that cannot meet the requirements of the new Regulation may
have to be approved to Reg.44.
Dual approval of products does mean there may be a potential conflict between the
current Reg.44 groups and the i-Size categories. The i-Size categories allow the
manufacturers to design the CRS to any stature and maximum mass restriction of
CRS+child•[33kg]. This could lead to conflicting child mass limits, which will confuse the
consumer when choosing a CRS and when checking compatibility with their vehicle.
Implementation of Phase 1 of the new Regulation will mean that CRSs that can be
installed using either ISOFix or the adult seat-belt can either be only approved to
Reg.44, or only approved as an ISOFix CRS to the new Regulation and a belt-attached
CRS to Reg.44. Potentially this could lead to three approval labels on a CRS. Also the
CRS could be classed as “semi-universal” in Reg.44 and “universal” in the new
Regulation (with alternative 3rd attachment point for CRSs with a support leg). This
would be confusing to the consumer and may cause vehicle compatibility issues,
especially with older vehicles.
ISOFix non-integral CRSs will remain approved to Reg.44 under Phase 1.
E.4.2.2 Phase 2
All integral and non-integral belt-attached CRSs will remain approved to Reg.44 under
Phase 2.
All ISOFix integral CRSs will be approved to the new Regulation.
These CRSs could be approved to Reg.44, or approved to the new Regulation as ISOFix
installed and to Reg.44 as a belt-attached restraint. This could lead to confusing the
consumer due to separate approval labels for ISOFix and belt attachments. Double
documentation will also be required, in terms of sizing and mass limits between the use
as an ISOFix CRS and a belt-attached CRS.
Manufacturers would have the choice whether they wish to approve this type of CRS to
the new Regulation, to Reg.44 or both, during Phase 2. At this stage it is unclear
whether a manufacturer would get a great benefit from approving their CRS to both
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regulations. Currently, in order for this type of CRS to enter the new Regulation as
“universal”, the belt and ISOFix anchorages will have to be aligned in the vehicle, to
avoid poor fitment of the seat-belt across the occupant. “Universal” also means that the
restraint fits all potential ISOFix vehicle positions (approved for the ISOFix CRS size
category), thus removing the need for vehicle application lists. Alternatively this
category could remain “semi-universal”.
As previously mentioned, during the dynamic testing of the CRSs, some products were
found to have compatibility issues with the new Regulation test bench and thus choose
to remain approved to Reg.44 until it is phased out. This does not encourage design
improvement. However, it is thought that new products will be designed to meet the
requirements of the new Regulation.
E.4.2.3 Phase 3
All remaining CRS types will be approved to the new Regulation and Reg.44 will cease to
exist. However, it may be very challenging for belt-attached CRSs to gain type approval
to the increased performance requirements proposed in the new regulation.
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Phase 1
Integral
CRSs
Restraint
category
Attachment
method
Approval
Regulation
ISOFix
only
New
Regulation
Reg.44
Non-integral
CRSs
ISOFix
or Belt
Belt
ISOFix
& Belt
Belt
Reg.44
Reg.44
Reg.44
Reg.44
Phase 2
Integral
CRSs
Restraint
Category
Non-integral
CRSs
Attachment
Method
ISOFix
only
ISOFix
or Belt
Belt
Approval
Regulation
New
Regulation
Reg.44
Reg.44
ISOFix
Belt
& Belt
New
Reg.44
Regulation
Phase 3
Integral
CRSs
Restraint
Category
Non-integral
CRSs
Attachment
Method
ISOFix
only
ISOFix
or Belt
Belt
ISOFix
& Belt
Belt
Approval
Regulation
New
Regulation
New
Regulation
New
Regulation
New
Regulation
New
Regulation
Figure 78 – Three phases of the single approval option
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Phase 1
Integral
CRSs
Restraint
Category
Attachment
Method
Approval
Regulation
ISOFix
only
New
Regulation
Reg.44
Non-integral
CRSs
ISOFix
or Belt
New
Regulation
& Reg.44
Reg.44
New Regulation
(ISOFix attached)
& Reg.44 (Belt attached)
Belt
ISOFix
& Belt
Belt
Reg.44
Reg.44
Reg.44
Phase 2
Integral
CRSs
Restraint
Category
Attachment
Method
ISOFix
only
Approval
Regulation
New
Regulation
Non-integral
CRSs
ISOFix
or Belt
Reg.44
New Regulation
(ISOFix attached)
& Reg.44 (Belt attached)
Belt
ISOFix
& Belt
Reg.44
New
Regulation
Belt
Reg.44
Phase 3
Integral
CRSs
Restraint
Category
Non-integral
CRSs
Attachment
Method
ISOFix
only
ISOFix
or Belt
Belt
ISOFix
& Belt
Belt
Approval
Regulation
New
Regulation
New
Regulation
New
Regulation
New
Regulation
New
Regulation
Figure 79 – Three phases of the dual approval option
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E.5 Specific areas of concern
E.5.1 Semi-universal category
One of the original aims of the new Regulation was to make all ISOFix restraints
“universal”, thus replacing the requirement for a vehicle application list. However, for
this to be achieved a 3rd alternative attachment point is required in the vehicle, for
restraints which currently use a support leg as the anti-rotation device. It has been
proposed that the simplest way to achieve this would be to define a range of dimensions
of the floor in relation to the ISOFix anchorages and make this consistent across all
vehicles. Restraint manufacturers would then have to ensure that their CRS was capable
of being adjusted to fit the defined range. However, it is unclear how this would be
applied retrospectively to the existing fleet.
In order for non-integral ISOFix CRSs to be “universal”, the adult belt and the ISOFix
anchorages need to be aligned in the vehicle (Reg.14), otherwise unsatisfactory
installation may occur. Again, whether this could be applied retrospectively to the
existing fleet is unclear. Keeping the “semi-universal” category for this type of restraint,
thus requiring a vehicle application list would solve this problem.
Therefore the introduction of these products into the new Regulation may have to be
delayed until the vehicle fleet is able to accommodate them correctly.
E.5.2 Vehicle specific category
The approval of vehicle specific CRSs will still be possible in the new Regulation.
However, how a vehicle-specific side impact test can be achieved poses a problem, due
to the requirement for an intruding door. One proposal is to use the results of a sledbased side impact test for the approval.
E.5.3 i-Size
Reg.44 mass groups ensure consistency amongst CRS sizing design in terms of mass
range and related age. The proposed i-Size categorisation of CRS in the new Regulation
will allow manufacturers the freedom to design the CRS for any size range they wish, as
long as the combined mass of the CRS and child do not exceed the defined limit (limit
not yet agreed). Therefore this has the potential that all CRSs in the market could be
different, designed to accommodate different sizes children. This causes a problem for a
consumer trying to compare CRSs, when they are all designed for different sized
children.
This also causes a problem when dynamically assessing the CRS. When testing a CRS in
Reg.44, the minimum and maximum sized dummy for each Reg.44 ECE Group (or
Groups) is used. According to the new Regulation, CRSs are tested with the minimum
and maximum sized dummy of the defined i-Size range. An intermediate dummy can be
tested if the installation of the CRS is substantially changed between the smallest and
largest dummy, e.g. rearward/forward facing CRSs. This is subjective and open to misinterpretation. The draft Regulation does not mention if the change from integral to nonintegral requires testing with an intermediate dummy, e.g. Group I-II-III. The Technical
Service is to choose which dummies will be appropriate to test with and this could lead
to variation across test houses.
E.5.4 Labelling
A different set of labels will be required on the CRS due to the fact that CRSs approved
to the new Regulation will have i-Size categorisation which is fundamentally different to
the Regulation 44 Group categorisation.
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Currently the Regulation 44 approval labels include:
•
ECE Regulation 44 Group(s) of the restraint
•
Mass range of the occupant for the restraint
The i-Size labels will include:
•
Minimum stature of occupant
•
Maximum stature of occupant
•
Maximum mass of occupant
However, CRSs such as those attached using ISOFix or the seat belt, could have dual
approval during Phase 1 of the new Regulation implementation. This means the CRS
would require three approval labels:
•
Regulation 44 universal for installation with the seat belt
•
Regulation 44 (semi-) universal for installation with ISOFix
•
new Regulation i-Size for installation with ISOFix
These labels could potentially contradict each other based on the different requirements,
of the Reg.44 mass range compared to the i-Size maximum mass and stature range,
thus confusing the consumer.
E.5.5 ISOFix vehicle compatibility
Although it is proposed that currently the ISOFix size classes will remain unchanged,
there remains an issue with the categorisation of CRSs in the new Regulation. Currently
in Regulation 44, ISOFix child restraint systems fall into several ISOFix size classes
described in Reg.16 Annex 17, Appendix 2, presented here in (Table 71).
Table 71: Reg.16 ISOFix size category
Reg.44 Mass
Group
Group 0
(0-10 kg)
Group 0+
(0-13 kg)
Group I
(9-18 kg)
TRL
ISOFix size category
Description
F
ISO/L1
Left Lateral Facing position CRS (carry cot)
G
ISO/L2
Right Lateral Facing position CRS (carry-cot)
E
ISO/R1
Rearward Facing infant CRS
C
ISO/R3
Full Size Rearward Facing toddler CRS
D
ISO/R2
Reduced Size Rearward Facing toddler CRS
E
ISO/R1
Rearward Facing infant CRS
A
ISO/F3
Full Height Forward Facing toddler CRS
B
ISO/F2
Reduced Height Forward Facing toddler CRS
B1
ISO/F2X
Reduced Height Forward Facing Toddler CRS
C
ISO/R3
Full Size Rearward Facing toddler CRS
D
ISO/R2
Reduced Size Rearward Facing toddler CRS
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Under the new i-Size categorisation, for a vehicle to be i-size ready it must be able to
accept forward facing ISOFix CRSs in the ISO/F3 category and rearward facing ISOFix
CRSs in the ISO/R2 category. However, limiting i-size approval to these sizes will mean
that several vehicles are not compatible with these CRSs because they are too small to
fit these size classes of restraints, whereas they are capable of fitting the small ISOFix
classes.
The vehicle handbooks will need to be updated to indicate which CRS types the vehicle
can support in each seating position. So in addition to the current Regulation 44 groups,
the handbook will have to indicate which i-Size CRSs the vehicle is compatible with.
Currently in Reg.44 those CRS which can be used rearward or forward facing must state
the maximum mass the occupant can remain rearward facing and the minimum mass
the occupant can travel forward facing. In Regulation 44 the mass groups for this type of
restraint are 0-13 kg and 9-18 kg. However, in the new Regulation the i-Size categories
will state that occupant should not be forward facing before 15 or 18 months. This
change will prevent very young children, who may be heavier than 9kg, from travelling
forward facing, which is perceived to encourage more appropriate CRS use.
The long term aim of changing the way CRSs are classified is to be less design restrictive
towards the manufacturers and to make choosing CRSs easier for the consumer. All
CRSs will have a height range and a maximum mass, defined by the manufacturer of the
CRS.
E.6 Summary
The main differences between the two potential approval routes, and the main issues for
both routes, are summarised in Table 72. The different approval routes and the issues
arising from them have different implications for three key groups of stakeholders:
consumers, CRS manufacturers, and car manufacturers. Some of the main issues for
each group are summarised below.
It may be complex to understand the labelling and instructions, and whether they apply
to particular vehicles. This is likely to be considerably more of a problem with dual
approval, which could require up to three sets of labels, multiple instructions and
multiple mass limits for a single CRS.
Car manufacturers will have to label which size of CRS and which CRS Regulation each
seating position is compatible with. This is a complex requirement for OEMs, and is likely
to be very difficult for consumers to understand. This would apply for both single and
dual approval routes.
ISOFix integral CRSs - Both routes lead to adoption of the new Regulation by the
beginning of Phase 2.
ISOFix non-integral CRSs - In this case, the dual approval route may slow the pace of
improvement in CRS safety, if maintaining Reg.44 approval is considered to be the
straightforward option by CRS manufacturers.
Overall, both routes lead to different types of restraint being approved to different
Regulations at different times, and therefore offering different levels of safety.
The potential combination of different vehicle seat labelling on each seat in multiple
vehicles; different CRS mass limits, CRS labels and instructions; and different approvals
for a single CRS is unlikely to reduce the already high incidence of misuse of CRSs.
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Belt-attached integral or non-integral CRSs - There is no difference between the single
and dual approval routes. It is not known how the belt-attached option would be
approved under the new Regulation once this becomes mandatory in Phase 3.
ISOFix integral CRSs - There is no obvious benefit to dual approval that would be
sufficient to justify the cost of meeting two sets of approval requirements and of
demonstrating conformity of production for both.
ISOFix-or-belt-attached integral CRSs - The most straightforward route is for
manufacturer’s to choose to continue to approve to Reg.44, because the alternative
requires multiple approvals and multiple CoP, as well as multiple labelling and
instructions which could be confusing to consumers and may therefore lead to an
increase in complaints and enquiries. The only obvious benefit to dual approval for this
CRS category would be if approval to the new Regulation was considered to be
prestigious. Overall, if Reg.44 is considered to be the more straightforward, lower-cost
option, CRSs may not be improved until Phase 3 is implemented, which will not
encourage design improvements in the short to medium term.
ISOFix non-integral CRSs - It is not known how the belt-attached option would be
approved under the new Regulation.
Issues for OEMs
ISOFix or belt-attached integral CRSs - Car manufacturers will have to label the size of
CRS and the CRS Regulations that each vehicle seating position is compatible with
(Reg.14 and Reg.16 will need amending).
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Table 72: Potential benefits and disbenefits if the proposed single approval or dual approval routes are used
Restraint type
Belted-attached
Integral or
non-integral
Phase
Single approval
Dual approval
Phase 1
Must be approved to Reg.44
Phase 2
Must be approved to the new Regulation
Currently unknown how belt-attached option would be
approved under the new Regulation
Manufacturer to choose to approve to Reg.44, or the new
Regulation
Manufacturer to choose to approve to Reg.44, or the
new Regulation, or both
Phase 3
Phase 1
•
May expect CRS with a long life-span to be
approved to the new Regulation
•
May expect low-cost CRS with a short life-span
and poor performing CRS to be approved to
Reg.44
ISOFix-integral
ISOFix-or-beltattached integral
May expect most CRS to be approved to the
new Regulation
Currently low numbers of this CRS type; may increase if
ISOFix-or-belt-attached CRS are phased out if the new
Regulation is more stringent
Currently low numbers of this CRS type; may increase if
ISOFix-or-belt-attached CRS are phased out if the new
Regulation is more stringent
Dual approval could lead to conflicting mass
requirements, which may be difficult for consumers to
understand
Phase 2
Phase 3
Must be approved to Reg.44 or
Currently the most common CRS type
Must be approved as ISOFix-attached to the new
Regulation and belt-attached to Reg.44
Could lead to a two-tier system: ISOFix-only perform
better, but ISOFix-or-belt-attached more attractive to
consumers because they are more likely to fit a second
vehicle
Phase 1
•
•
•
CRS manufacturers may focus on this type due to
popularity/flexibility, but
This would mean the new Regulation only applies
to a minority of CRS
Car manufacturers will have to label which size of CRS and
which CRS Regulation each seating position is compatible
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•
CRS could be semi-universal in Reg.44 and
universal in the new Regulation (if a third
attachment point is defined), which could
o
Be confusing for consumers
o
Cause compatibility issues, especially with
older vehicles
May lead to multiple mass limits, approval labels
and sets of instructions, which may be confusing
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Restraint type
Phase
Single approval
Dual approval
with
•
for consumers
Complex requirement for OEMs to implement and
labelling would have to be applied for many years
Difficult for consumers to understand
Car manufacturers will have to label which size of CRS
and which CRS Regulation each seating position is
compatible with
•
Complex requirement for OEMs to implement
and labelling would have to be applied for many
years
Difficult for consumers to understand
Must be approved to Reg.44 or
Ditto Phase 1
Must be approved as ISOFix-attached to the new
Regulation and belt-attached to Reg.44
Phase 2
Ditto Phase 1
Phase 3
Phase 1
Manufacturer to choose to approve to Reg.44, or the
new Regulation, or both
Intended to be universal under the new Regulation so that
a vehicle application list is not required
•
Phase 2
Requires seat-belt and ISOFix anchorages to be
aligned which is not the case for all vehicles
•
ISOFix nonintegral
Requires seat-belt and ISOFix anchorages to be
aligned which is not the case for all vehicles
Some CRS may have compatibility issues with the new
Regulation, so may choose to remain with Reg.44 until
Phase 3, which does not encourage design improvement
Phase 3
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Currently semi-universal under Reg.44; intended to be
universal under the new Regulation so that a vehicle
application list is not required
Ditto Phase 2
Ditto Phase 2
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Appendix F
Indications of the potential costs and
benefits
F.1 Introduction
In 2007, the World Forum for Harmonization of Vehicle Regulations (WP 29) agreed to
the establishment of a new GRSP Informal Group on Child Restraint Systems (CRSs).
The remit of this Group is to consider the development of a new regulation for,
GRSP. The aim is that this new regulation will contain front, side and rear dynamic
impact assessments and will utilise a new family of child anthropometric devices for the
assessment of the performance of CRSs.
This report describes the results of an indicative cost-benefit analysis of the various
regulatory proposals and options. It draws together available information on European
child car occupant accident statistics, along with more detailed GB casualty data, and
data gained on volume sales to provide an indication of the likely costs and benefits of
the new regulation.
F.2 Casualty valuations
Putting a financial value on a human life or the prevention of a serious injury is
notoriously difficult and controversial. Whilst no EU27 wide figures are currently
available, each Member State necessarily uses its own figures for assessing the benefits
of proposed safety measures. Methods of doing this vary, and there is as a result
substantial variation in the figures used. In 2002, for example, the FP6 HEATCo project
(Harmonised European Approaches for Transport Costing and Project Assessment) found
fatality valuations ranging from €275,000 to €2.9million (HEATCO, 2006).
The generally accepted method of valuing casualties combines the actual costs and lost
output with a societal Willingness to Pay (WTP) amount, which reflects how much people
generally would be willing to pay to avoid the pain, grief and suffering associated with a
bereavement or injury. Fatality valuations performed in this way tend to be at the upper
end of the range quoted above, the UK fatality valuation in 2002, for example, was
€1.8million. For the purposes of this project, the UK valuations are considered to
represent reasonable EU estimates. The most recent UK casualty valuations are shown in
Table 73.
Table 73: UK casualty valuations, 2008 (DfT, 2009)
Casualty severity
Cost per casualty (£)
Killed
1,683,800
Serious
189,200
Slight
14,600
With the ongoing turmoil in financial markets across the world, the Pound:Euro exchange
rate has been subject to quite significant variability over recent years. At the time of
writing this report, the rate was about €1.16 to the £1, but had in the preceding three
years been as low as €1.07 and as high as €1.45 (a value that was its steady-state for
about 4 years prior to the start of the turmoil in 2007). Assuming a future long-term
trend rate of €1.25 to £1 seems reasonable and produces the € casualty valuations
shown in Table 74.
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Table 74: Estimated EU casualty valuations
Casualty severity
Cost per casualty (€)
Killed
2,105,000
Serious
236,500
Slight
18,250
These are thus the figures used to quantify the EU27 wide casualty prevention benefits
of the proposed regulatory options. They fall comfortably within the wider range of
valuations used in Member States.
No allowance is made for the future effects of inflation or GDP growth (a society tends to
be willing to pay more for casualty prevention as its overall wealth increases), nor of any
age-related effects, e.g. that society may well place a higher than average value on the
grief and pain associated with a child casualty. Such uncertainties and limitations with
the casualty saving calculations are beyond the scope of this project. It is worth noting,
however, that in attempting to allow for such uncertainties and approximations, the
HEATCo project recommends that casualty benefits calculations are subjected to a
sensitivity analysis by applying valuations in the range v/3 to 3v, where v is the central
estimate. Whilst this recommendation is also considered outside of the scope of this
project, it would mean that the true benefits calculated could be as high as 200% higher
than the central estimates quoted (equivalent to a fatality valuation of about €6million),
and as low as 67% lower (€700,000 fatality valuation).
F.3 Options for assessment
The likely costs and benefits of three regulatory options are analysed, and are described
in the following sections.
F.3.1 Option 1 – Q series dummies, existing frontal impact test
This option represents the minimal regulatory change being considered. It involves
keeping the existing (UNECE Regulation 44) frontal impact test (which uses a crash pulse
originally developed in the 1970s), but replaces the P-series dummies with the more biofidelic Q-series devices, and makes use of this enhanced bio-fidelity by setting
performance criteria for the neck loadings and chest compression (in addition to the
head excursion and chest acceleration already regulated). In terms of injury prevention,
this option would thus help to reduce neck and chest injuries in frontal impacts only. This
option would also, it is assumed, implement changes to the head excursion limits
currently permitted, thus also helping to prevent some head and face injuries in frontal
impacts.
F.3.2 Option 2 – plus a side impact test
procedure (the existing regulation 44 has frontal and rear impact tests only). This would
thus have additional benefit (over and above Option 1) for casualties involved in side
impacts only.
F.3.3 Option 3 – with a new, more representative frontal impact test
Driven largely by legislation, consumer information programmes, technological
innovation and heightened consumer demand for safer vehicles, the impact absorbing
structures and occupant protection systems of cars have changed radically over the last
three or four decades. Front and side structures tend to be stiffer, meaning higher forces
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are transmitted through them in an impact. Higher forces also mean higher
decelerations. It is, therefore, unlikely that the crash pulse (50 km/h frontal impact)
used in the existing Regulation 44 (based on data from crash tests carried out in the
1970s) is representative of crash pulses typically experienced by occupants of modern
vehicles. This option corrects this anomaly, and can thus be expected to offer some
additional casualty reduction benefit (over and above Option 1) in frontal impacts only.
F.4 Target populations
The following sections present an analysis of recent casualty data, both from Great
Britain (the UK excluding Northern Ireland) and from other EU Member States, and uses
those data to derive estimates of the overall annual numbers of child car occupant
casualties (aged under 12) across the EU27. These numbers (of killed, serious and slight
casualties) define the overall target populations for CRSs, i.e. the total numbers that
could potentially be prevented.
It should be noted that these target populations are not estimates of actual casualty
savings from CRS use; they would only be equivalent to such estimates in the extremely
unlikely scenario that all CRSs were 100% effective (i.e. they always saved the life or
prevented the injury regardless of the accident conditions) and used 100% of the time
(i.e. all child car occupants wore correctly fitted CRSs at all times). They are useful,
however, in setting the baseline scenario, from which more realistic estimates of actual
savings from each regulatory option are made.
F.4.1 GB casualty data
Details of all GB road accidents (involving an injury and reported to the police) are
recorded in the national STATS19 database. The UK Department for Transport (DfT)
publishes summary statistics from this database every year. Within that summary is a
breakdown of the numbers of children, in various age groups, killed or injured while
travelling as a car passenger, and for all road users. Table 75 shows the data for child
car occupants aged under 12, and the total number of road user fatalities.
Table 75: GB casualty data, 2006-2008
Severity
Age
Group
Casualty type
2006
2007
2008
Average
Killed
<12
Car passengers
26
28
31
28
Serious
<12
Car passengers
277
243
258
259
Slight
<12
Car passengers
6,147
5,658
5,466
5,757
All
<12
Car passengers
6,450
5,929
5,755
6,045
Killed
All
All
3,172
2,946
2,538
2,885
It can be seen that in Great Britain between 2006 and 2008, 28 children aged under 12
were killed on average each year while travelling as car passengers, representing 0.97%
of the 2,885 killed in all road accidents on average each year.
It can also be seen that for each fatality there were, on average 9.25 seriously injured
child casualties (=259/28) and 206 slightly injured children (=5757/28). It should also
be noted that these data are based on the STATS19 database, i.e reported accidents
only. They are, therefore, very much a lower estimate of the true casualty figures
because inevitably some injury accidents do not get reported to the police. Whilst
previous research suggests that the extent of under-reporting in the UK is far less than
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in some other countries, it also suggests that some allowance for under-reporting should
be made when making national casualty estimations. Recent estimates (reported as part
of the HEATCo project) suggest that UK serious injuries are under-reported by a factor of
somewhere between 1.1 and 1.18, and slights by between 1.22 and 1.43. While there is
no discernible under-reporting of fatal injuries, the HEATCo project further described how
a correction factor of 1.02 was needed for fatality estimates to allow for those deaths
directly attributable to the accident but occurring more than 30 days after the accident
(these are not counted as fatalities in the official statistics but of course involve just as
much pain, grief and suffering as those that occur less than 30 days after the accident
and should, therefore, be valued similarly). These findings are combined in Table 76 to
provide both lower (based on STATS19 only) and upper annual estimates for Great
Britain. The upper numbers use factors of 1.02 for the fatalities, 1.15 for the serious
injuries and 1.3 for the slight injuries.
Table 76: Lower and upper annual GB casualty estimates, child car occupants
<12 year old
Killed
Serious
Slight
All severities
Lower
estimate
28
259
5,757
6,045
Upper
estimate
29
298
7,484
7,811
The following section uses these data to estimate equivalent EU27 numbers.
F.4.2 EU27 casualty data and estimates
Very detailed data on child car occupant casualties and restraint use are not available
from all EU27 Member States, so other data sources will be needed to estimate the
numbers involved. There are various methods by which such estimates can be made, but
it is impossible to know whether any one of them gives a more accurate estimate of the
true numbers than any other. For this reason, it is suggested that a variety of different
methods be used and combined together to indicate the likely range. Three such
methods are described in the following sections.
F.4.3 EU27 Estimate Method 1 – GB data weighted by all road user fatalities
What is generally believed to be a reliable and accurate measure of the total number of
road user fatalities in each Member State is published each year by the European
Commission (DG TREN Pocketbook, 2010). Fatalities tend, unsurprisingly, to have a very
high likelihood of being reported and thus be recorded in official statistics, unlike lower
severity accidents which often (how often varies between Member States) go
unreported. Given that car designs are globally manufactured and distributed products,
they tend not to vary very much between countries. It is therefore reasonable to assume
that the numbers of fatal, serious and slight child casualties in the EU27 are distributed
in a similar way to the GB case. It is thus possible to estimate the EU27 child car
occupant casualty numbers by simply factoring up the GB estimates shown in Table 76
by the ratio of all EU27 fatalities to the total GB fatalities number.
According to the 2010 Pocketbook, between 2006 and 2008 there were, on average,
41,478 road user fatalities per year across the EU27, compared with 2,885 in GB (Table
75), giving a weighting factor of 14.38 (=41478/2885). Table 77 shows the resulting
EU27 estimates.
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Table 77: Lower and upper annual EU casualty estimates, child car occupants
<12 years old, Method 1
Killed
Serious
Slight
All severities
Lower
estimate
403
3,724
82,786
86,913
Upper
estimate
417
4,285
107,620
112,322
F.4.4 EU27 Estimate Method 2 – GB data weighted by car occupant fatalities
For all but three Member States (Bulgaria, Lithuania and Slovakia), the 2010 Pocketbook
also gives the numbers of car occupant fatalities for the latest available year (ranging
from 2005 to 2008). On average, from the countries where data is available, about 50%
of all road user casualties are car occupants. Using this percentage to estimate the
numbers for the three countries, and adding those estimates to the known numbers for
the 24 other Member States, gives a total for the EU27 of 19,350 fatalities per year.
Data is only available for individual years (mostly 2007 or 2008), which vary from one
country to another, so using this figure as an annual average assumes that the
combined data is representative of the 2006-2008 average. The 2006-2008 average for
GB is 1,434 car occupant fatalities per year, giving a weighting factor of 13.49
(=19350/1434). Table 78 shows the resulting EU27 estimates.
Killed
Serious
Slight
All severities
Lower
estimate
378
3,494
77,662
81,534
Upper
estimate
391
4,020
100,959
105,370
F.4.5 EU27 Estimate Method 3 – GB data weighted by EU18 child car occupant
fatalities and EU27 child road user fatalities
Analysis of the CARE database (which also provides the EU27 statistics quoted in the
preceding sections) and reported by the European Road Safety Observatory (ERSO,
2007) found that on average across the EU185, in 2005, 41% of all child road fatalities
(aged <16) were car occupants (the latest year for which data is available). It further
reports that, on average across the EU146 in 2005, 3.6% of all road user fatalities were
aged under 16.
More recent (2008) CARE data on child road fatalities suggests there were about 1,036
casualties aged <15 in the EU247 in 2008, and 1,260 aged 15-17. Comparing the 2005
data for <16 with the equivalent data from 2005 for the <15 and 15-17 age groups
suggests that about 20% of the 15-17 year old fatalities are <16. Applying this figure to
the 2008 data suggests there were about 1,288 road fatalities aged <16 in EU24 in 2008
(= 1036 + 0.2x1260). Assuming that 3.6% of all road user casualties in the three other
5
EU18 = EU27 minus Bulgaria, Czech Republic, Germany, Cyprus, Latvia, Lithuania, Romania, Slovenia and
Slovakia.
6
EU14 = EU18 minus Estonia, Hungary, Malta and Poland.
7
EU24 = EU27 minus Bulgaria, Cyprus and Lithuania
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Member States were aged <16 suggests there were 1,347 such casualties across the
EU27 in 2008.
If it is further assumed that 41% of those casualties were car occupants (as was found in
2005 for EU18), then approximately 552 children aged under 16 died in accidents while
car occupants across the EU27 in 2008. The corresponding figure for GB is 49 fatalities in
2008, giving a weighting factor of 11.27 (=552/49). Table 79 shows the resulting EU27
estimates.
Killed
Serious
Slight
All severities
Lower
estimate
316
2,919
64,881
68,116
Upper
estimate
327
3,358
84,345
88,030
F.4.6 Summary of EU casualty estimates
Table 80 gives the overall range of casualty estimates for the EU27 arising from the
three methods described above, and which thus form the overall target populations for
CRSs. Applying the casualty valuations derived earlier (Table 74) implies that the
societal cost of these casualties is somewhere between €2.5billion and €3.9billion per
year.
<12 years old
Killed
Serious
Slight
All severities
Lower
estimate
316
2,919
64,881
68,116
Upper
estimate
417
4,285
107,620
112,322
F.5 Benefits estimate
The following sections provide estimates of the likely casualty savings, in both human
and monetary terms, from the various CRS regulatory options described in section F.3.
It is important to note that such estimates can only be regarded as, at best, indicative.
Only very detailed and in-depth accident studies, involving a large number of cases,
could hope to provide a truly robust assessment of the likely effectiveness of new CRS
design and performance options. Such in-depth studies, involving the accurate
simulation and modelling of real-world collisions and injury mechanisms, is well beyond
the scope of this project. Even with such analyses, of course, one cannot be absolutely
certain that the accidents studied are truly representative of future collision scenarios.
The indicative methods described more fully in the following sections use a combination
of summary data from previous published in-depth studies and data indicating the
effects of past legislative changes. Estimates are then further modified with assumptions
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about what proportion of child car occupants would be likely to be using a correctly fitted
CRS.
F.5.1 Effects of previous legislative changes
The effects of past legislative changes with regard to seat belt use and CRS design were
analysed by TRL for the EC’s CHILD project (Visvikis et al., 2008). When looking at GB
national casualty data, it was found that two step changes (reductions) in the annual
numbers of child car passenger casualties were evident; one that matched the mandated
wearing of rear seat belts in 1989 and the other corresponding to implementation of the
03 series of amendments to UNECE Regulation 44 in 1998. The averaged percentage
casualty reductions found, by severity, are shown in Table 81. Given that both of these
measures were likely to only significantly affect frontal impacts, the percentage
reductions shown (which are for all impact types) could reasonably be expected to have
been even higher for the target populations (i.e. frontal impact casualties only).
Research for the NPACS project (Cheung and Le Claire, 2006) showed, for example, that
frontal impacts account for about 50 per cent of child car occupant casualties, suggesting
that the effectiveness of the legislative changes could be as high as double the
percentages shown in Table 81.
Table 81: Step change effects in GB of previous legislative changes
Casualty
severity
Killed
Serious
Slight
Minimum
reduction (%)
10.7
12.2
1.5
Maximum
reduction (%)
24.7
17.9
4.6
Average
reduction (%)
17.7
15.1
3.1
It is also appropriate to note, however, that the law of diminishing returns is likely to
apply, i.e. that further legislative changes may not have as much of an effect as past
changes, because the remaining casualties are those that are particularly hard to
prevent, e.g. they arise from very high speed/high energy impacts or because some
parents/guardians/drivers choose not to make proper use of the CRSs available for the
children in their care.
F.5.2 Usage rates
Another important determinant of the effectiveness of CRS legislation is the wearing
rate, i.e the proportion of children that correctly use a CRS in practice. In the UK,
wearing rates are routinely surveyed, and in 2009, about 70% of children (aged < 10)
were in a correctly used child seat or booster seat/cushion, up from about 40% when
surveying began in 2005. This level of detail is not available elsewhere in the EU, but
surveys of seat belt use show rates varying between about 80-95% for front seat
passengers (all ages) and 25-75% for rear seat passengers.
Seat belt use in general, and child restraint use in particular, are believed to be rising
steadily, in response, for example, to co-ordinated public safety campaigns. While some
countries, e.g. the UK, may well aspire to CRS usage rates of 80% or more in the next
few years, others are likely to be some way behind. For the purposes of this project, it is
assumed that a rate of 60% is the likely overall average rate across the EU27.
F.5.3 Option 1 – Q series dummies, existing frontal impact test
This option would deliver some additional benefits (over and above existing restraint
designs) through the provision of new performance limits in additional body regions,
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reflecting the enhanced capabilities of the Q-series dummies. It would mitigate some
head, face, neck and chest injuries not preventable by existing CRS designs.
These changes are assumed to be similar in magnitude to previous legislative changes,
e.g. the adoption of the 03 series of amendments to UNECE Regulation 44 which led to
one of the step changes in the numbers of GB child car occupant casualties described in
section F.5.1. Although such changes led to reductions of anything up to 25% (for all
casualty types, so perhaps as high as 50% for those in frontal impacts), the law of
diminishing returns might mean that future changes are not quite so dramatic. For the
purposes of this (indicative) cost benefit analysis, it is assumed that this option would:
•
Convert 10% of frontal impact fatalities to serious injuries;
•
Convert 12% of frontal impact serious injuries to slight injuries;
•
Convert 2% of the frontal impact slight injuries to uninjured.
If it is further assumed that frontal impacts account for 50% of all child car occupant
casualties, of all severities, and a CRS usage rate of 60% applies, then the overall
benefits of this option would be as shown in Table 82.
Table 82: Likely casualty and monetary benefit estimates of option 1, EU27
Severity
Potentially
preventable
Actually prevented
€m valuations
(note 2)
(note 3)
(note 1)
Lower
Upper
Lower
Upper
Lower
Upper
Killed
95
125
10
13
18.7
24.3
Serious
876
1286
105
154
22.9
33.6
Slight
19,464
32,286
389
646
7.1
11.8
All
20,435
33,697
504
813
48.7
69.7
Note 1 – assumes 50% of target populations are in frontal impacts and 60% use CRSs
Note 2 – assumes mitigation of 10% fatalities, 12% serious, 2% slights
Note 3 – uses valuations given in Table 75 (and each casualty reduced by one severity
level)
F.5.4 Option 2 – plus a side impact test
This option is the same as option 1 but for the addition of a side impact test. Previous
accident studies (for the NPACS project) found that about 20% of child car occupant
casualties were in side impacts. The assumed coverage of this option is thus 70% of all
casualties (the 50% for frontal impacts used in option 1 plus the extra 20% for side
impacts). If all other option 1 assumptions about usage rates and effectiveness are
retained, then the overall benefits would be as shown in Table 83.
Severity
Potentially
preventable
Actually prevented
€m valuations
(note 2)
(note 3)
(note 1)
Lower
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182
Upper
Lower
Upper
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Killed
133
175
13
18
24.3
33.6
Serious
1,226
1,800
147
216
32.1
47.1
Slight
27,250
45,200
545
904
9.9
16.5
All
28,609
47,175
705
1,138
66.3
97.2
Note 1 – assumes 70% of target populations are in side or frontal impacts, 60% use
CRSs
Note 2 – assumes mitigation of 10% fatalities, 12% serious, 2% slights
level)
F.5.5 Option 3 – with a new, more representative frontal impact test
This option would enact a more significant change to the frontal impact test procedure
(over and above the changes described under option 1), providing a test procedure that
is more representative of modern vehicles and thus more likely to prevent casualties
amongst occupants of those vehicles. Although the overall numbers of casualties
potentially preventable would be unchanged from option 2, it seems reasonable to
assume that the step change effects would be slightly higher than assumed for the other
options. It is thus assumed that this option would:
•
Convert 20% of frontal impact fatalities to serious injuries;
•
Convert 15% of frontal impact serious injuries to slight injuries;
•
Convert 4% of the frontal impact slight injuries to uninjured.
Applying these new effectiveness factors to the frontal impact casualties, and keeping
the factors the same as option 2 for the side impact casualties gives the overall benefits
shown in Table 84.
Severity
Potentially
preventable
Actually prevented
€m valuations
(note 2)
(note 3)
(note 1)
Lower
Upper
Lower
Upper
Lower
Upper
Killed
133
175
22
30
41.1
56.1
Serious
1,226
1,800
173
255
37.8
55.7
Slight
27,250
45,200
935
1,549
17.1
28.3
All
28,609
47,175
1,130
1,834
96.0
140.1
Note 1 – assumes 70% of target populations are in side or frontal impacts, 60% use
CRSs
Note 2 – assumes mitigation of 20/10% fatalities, 15/12% serious, 4/2% slights for
frontals/side impacts respectively
level)
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F.5.6 Summary of benefits estimates
The lower and upper likely annual casualty prevention benefits, in €m, for the EU27 can
be summarised as follows:
Option 1: €49m - €70m;
Option 2: €66m - €97m;
Option 3: €96m - €140m
F.5.7 Costs estimate
Manufacturers would be likely to incur additional costs in product development, product
testing and production, over and above existing CRS designs, if new legislative
requirements are placed on their products. These costs would in most cases be passed
on to consumers. The full extent of these additional costs depends largely on two factors
– the size of the market (i.e. the numbers of CRSs sold each year across the EU27) and
the per unit additional costs.
F.5.8 Market size
Unpublished data provided by industry for the purposes of this project suggests that in
the UK in 2009, about 1.53million car seats were sold to UK consumers. This is
equivalent to about 1.9 CRSs for every child born (there were about 794,000 births in
the UK in 2008). In France, the same sources suggest that 1.09million car seats were
sold, at a rate of about 1.3 seats per birth (835,000 births in France in 2008).
These variations are likely to be due to variations in restraint usage rates. If the 1.9
CRSs per birth for the UK corresponds to the measured current usage rate in the UK of
70%, then it is possible to estimate that an EU27 wide usage rate of 60% (as assumed
in the benefits estimations) would dictate that 1.6 CRSs per birth are needed (=1.9 x
60/70). Official (Eurostat) statistics indicate there were about 5.4million births in the
EU27 in 2008, which would imply a total market size of about 8.6million CRSs to be sold
each year.
F.5.9 Marginal (per unit) costs to manufacturers
It is likely that there will be quite significant variations in the costs incurred by
manufacturers, and passed on to consumers, as they will depend on a number of factors,
including:
•
The extent to which existing designs already exceed current requirements and
would need to be modified to pass the new ones;
•
The existing profit margin and the effects of any increased prices on that
products’ competitive positioning relative to other products;
•
The capability and capacity of the manufacturer to develop and manufacture new
designs cost effectively.
Earlier research (Visvikis et al., 2008)) estimated that the annual costs to UK
manufacturers of various CRS options being considered varied between £0.3m and
£4.9m. These costs include additional tests and product development costs and imply a
per unit cost of between 20p and £3.27 for the 1.5million units sold each year in the UK.
Other recent unpublished research for the UK Department for Transport (2008)
suggested costs of between 15p and £5.75 per unit.
Information provided in confidence by one major CRS manufacturer for this project gives
indicative costs (for an option 2 type scenario) of about €1.5 to €2 per CRS, which is
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comfortably within the ranges suggested by the earlier research. It is outside of the
scope and capability of this project to undertake detailed analyses of the costs
associated with each regulatory option, so for the purposes of this indicative study it is
assumed that:
•
Option 1 would cost between €0.5 and €1.5 per unit;
•
Option 2 would cost between €1.5 and €2.5 per unit;
•
Option 3 would cost between €2 and €5 per unit
F.5.10 Summary of cost estimates
Although it is possible that the costs incurred by manufacturers would not be wholly
passed on to consumers, it is also possible that the enhanced capabilities of the new CRS
designs are used to justify additional retail price increases (on the back of marketing as
improved, safer products). Information provided by industry as part of this project
suggests that overall mark-ups of about 30% are typical for existing CRS designs. For
the purposes of this project a range of mark-ups from 10% to 30% are assumed.
Applying the per unit costs of each option in section F.5.9 to these cost-to-consumers
mark-up rates and the market size estimate of 8.6million CRSs per year gives annual
total likely cost estimates of:
•
•
•
o
Lower estimate: 0.5x1.1x8.6 = €4.7m
o
Upper estimate: 1.5x1.3x8.6 = €16.8m
o
Lower estimate: 1.5x1.1x8.6 = €14.2m
o
Upper estimate: 2.5x1.3x8.6 = €28.0m
Option 3 - with a new, more representative frontal impact test
o
Lower estimate: 2x1.1x8.6 = €18.9m
o
Upper estimate: 5x1.3x8.6 = €55.9m
F.5.11 Benefit:Cost ratios
Combining the estimates derived in sections F.5 and F.5.7, gives the overall ranges of
estimated benefit-cost ratios shown in Table 85. The lower limits of these ranges are
calculated by combining the lower benefit estimates with the upper cost estimates, and
the upper limits are calculated by dividing the upper benefit estimates into the lower cost
estimates.
Table 85: Summary of benefits and costs for each option
Option
Option 1
Option 2
Option 3
TRL
Benefits (€m)
Lower
Upper
48.7
69.7
66.3
97.2
96.0
140.1
Costs (€m)
Lower
Upper
4.7
16.8
14.2
28.0
18.9
55.9
185
Benefit:Cost ratios
Lower
Upper
2.9 :1
14.8 :1
2.4 :1
6.8 :1
1.7 :1
7.4 :1
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It must be emphasised that these figures are necessarily based on various assumptions,
as described in the earlier sections, and are therefore subject to considerable
uncertainty. It is apparent, however, that the broad indications from this study are that
the benefit to cost ratios of all the options being considered are likely to be positive, i.e.
the benefits derived from reduced casualties are likely to exceed the extra costs incurred
by EU27 consumers, by a factor of somewhere between 2 and 15, depending on which
option is chosen.
F.6 Summary
In 2007, the World Forum for Harmonization of Vehicle Regulations (WP 29) agreed to
the establishment of a new GRSP Informal Group on Child Restraint Systems (CRSs).
The remit of this Group is to consider the development of a new regulation for,
GRSP.
This report describes the results of an indicative cost-benefit analysis of the various
regulatory proposals and options. It draws together available information on European
child car occupant accident statistics, along with more detailed GB casualty data, and
data gained on volume sales to provide an indication of the likely costs and benefits of
the new regulation.
This option involves keeping the existing (UNECE Regulation 44) frontal impact test, but
replaces the P-series dummies with the more bio-fidelic Q-series devices, and makes use
of this enhanced bio-fidelity by setting performance criteria for the neck loadings and
chest compression. In terms of injury prevention, this option would thus help to reduce
neck and chest injuries in frontal impacts only. This option would also, it is assumed,
implement changes to the head excursion limits currently permitted, thus also helping to
prevent some head and face injuries in frontal impacts.
Option 2 - plus a side impact test
procedure (the existing regulation 44 has frontal and rear impact tests only). This would
thus have additional benefit (over and above Option 1) for casualties involved in side
impacts only.
The impact absorbing structures and occupant protection systems of cars have changed
radically over the last three or four decades. It is, therefore, unlikely that the crash pulse
(50 km/h frontal impact) used in the existing Regulation 44 (based on data from crash
tests carried out in the 1970s) is representative of crash pulses typically experienced by
occupants of modern vehicles. This option corrects this anomaly, and can thus be
expected to offer some additional casualty reduction benefit (over and above Option 1)
in frontal impacts only.
Three different methods of estimating the numbers of child (aged under 12) car
occupant casualties each year in the EU27 have been used, all based on applying
weighting factors to GB data. Applying casualty valuations to the overall range
estimated, also derived from GB data, indicates a societal cost of somewhere between
€2.5billion and €3.9billion per year.
Data from child restraint usage surveys and accident analyses are used to estimate that
50% of child car occupant casualties are from frontal impacts, 20% are from side
impacts, and to speculate that an overall future usage rate of 60% is a reasonable
assumption for the EU27. These data are combined with the measured casualty
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reduction effects of previous legislative changes to produce EU27 estimates of the
benefits of the various options.
Demographic data and information provided by the CRS industry are combined to
produce estimates of the likely costs (to consumers) of implementing the various
options, based on costs incurred by manufacturers for new product development and
testing.
Combining the benefit and cost estimates gives the overall ranges of estimated benefitcost ratios shown in Table 86.
Table 86: Summary of benefits and costs for each option
Option
Option 1
Option 2
Option 3
Benefits (€m)
Lower
Upper
48.7
69.7
66.3
97.2
96.0
140.1
Costs (€m)
Lower
Upper
4.7
16.8
14.2
28.0
18.9
55.9
Benefit:Cost ratios
Lower
Upper
2.9 :1
14.8 :1
2.4 :1
6.8 :1
1.7 :1
7.4 :1
These figures and ratios are necessarily based on various assumptions, as described in
the main body of this report, and are subject to considerable uncertainty. It is apparent,
however, that the broad indications from this study are that the benefit to cost ratios of
all the options being considered are likely to be positive, i.e. the benefits derived from
reduced casualties are likely to exceed the extra costs incurred by EU27 consumers, by a
factor of somewhere between 2 and 15 to one, depending on which option is chosen.
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Regulations and Standards
Regulation No. Synthesis Draft 2010_02_iSize – uniform provisions concerning the
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GRSP Working Group documents
The following list contains the references used from documents submitted to the GRSP
informal working group for child safety. Where the reference code means:
CRS-03-05
Working Group
Document Number
Meeting Number
•
•
•
Working group “CRS” – Child restraint system
First number is the meeting
Second number is the order in which the document was submitted at that
meeting
Document
Presented by
Title
CRS-03-05
TRL
Vehicle environment
CRS-03-06
Mercedes-Benz
GRSP working group child restraints:
Location of ISOFIX-/Top tether anchorages
Location of Cr-Point
CRS-03-07
OICA
OICA data on floor position
CRS-03-12
JPMA/Vehicle
Manufacturer LATCH WG
Status Update
CRS-03-14
FTSS
Q-dummies ready to enter regulations
CRS-03-17
DOREL
Isofix Loads Measurements
CRS-04-03
UTAC
Vehicle Deceleration Pulses
CRS-05-03
TRL
NPACS test bench
CRS-05-04
DOREL
CRS-06-02
TRL
Test bench
CRS-06-03
Mercedes-Benz
GRSP working group child restraints: Load
levels in anchorage system
CRS-07-02
Britax
Load levels in ISOFIX anchorages
CRS-07-03
DOREL
CRS-07-07
UTAC
Vehicle Deceleration Pulses
CRS-09-09
TRL
Contribution to the definition of the test seat
CRS-10-03
DOREL
Presentation of a Side impact Step 1
proposal
CRS-10-06
VTI
3rd ISOFIX anchorage
CRS-14-04
Britax
Side Impact Activity Britax Römer
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Analysis for the development of legislation on child occupant

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