LaRa-OHVD: An Innovative Over-Height Vehicle Detection - ITS-NY

LaRa-OHVD: An Innovative Over-Height Vehicle Detection System to
Protect our Bridges to Prosperity
Abhishek Singhal, Ph.D. Candidate in Transportation Engineering
The City College of New York
A student essay submitted for ITS- NY 2015 Best Student Essay Competition at
2015 Intelligent Transportation Society of New York 22nd Annual Meeting
Saratoga Springs, NY
LaRa-OHVD: AN INNOVATIVE LASER RANGING OVER-HEIGHT VEHICLE
DETECTION SYSTEM TO PREVENT BRIDGE STRIKES
Abhishek Singhal, Ph.D. Candidate in Transportation Engineering, [email protected]
Advisor: Prof. Camille Kamga, Ph.D., [email protected] Co-Advisor: Prof. Anil K. Agrawal, Ph.D., P.E., [email protected]
Department of Civil Engineering, The City College of New York, CUNY, NY 10031
1. RESEARCH OBJECTIVES
2. BRIDGE HIT PROBLEM
3.CURRENT MITIGATION METHODS
 ~5,000 over-height vehicle bridge hits/year in U.S. result in over
$100 million worth of damage to public & personal property
 Over-height truck bridge hits resulted in ~20 fatalities (2003-2013)
and 75 injuries (2010-2013) per year respectively.
 Over-height trucks have resulted in 13,108 structural damage
bridge hits in four years (2010-2013).
 Societal cost of a major over height vehicle-bridge hit estimated to
be $694,000 based on 1994 FHWA figures.
 14 European Union Member States, Ireland (>180 hits/year), United
Kingdom (>2,000 hits/year), Australia (332 hits between 2005-2013)
consider bridge hits as a significant safety risk.
 68% State DOTs consider bridge
hits to be a significant problem.
 New York State had 1,600 hits
since 1993. Many bridges have
been repeatedly hit.
 Tractor trailers, large trucks
constitute majority (98%) of hits.
 Bridges over Parkways, State
Number of recorded bridge hits
Highways, Interstates most affected New YorkbyState:
year (* Through 4/20/2015)
PROBLEM STATEMENT
 Over-height vehicle bridge strikes a major problem all over the world.
 More than 200 bridge hits annually in New York state.
 Current Over-Height Vehicle Detection Systems (OHVDs) are installed across
the road width up to quarter mile (1320 feet) before the bridge.
 System & installation costs significantly high (up to $200,000 in some cases).
 Installation limited to very few locations.
 No innovation in OHVDS technology in U.S. since 1998
RESEARCH OBJECTIVES
 To develop a new over-height vehicle detection system that can be installed
on the face of the bridge/overhead gantry/existing roadside infrastructure .
 Can detect incoming over-height vehicle at safe stopping distance.
 Most bridges already have electricity (street lights), telephone connections.
 Low cost device based on mature LADAR (Laser Detection and Ranging)
technology, special optics and existing traffic engineering guidelines.
 Mass deployment because of low cost.
 Better performance features than existing OHVD systems.
Target
Driver
30 States
44 States
United States: Number of Bridge Hits between 2005-2008
March 2, 2015, FREE!
Region 5
Region 11









An eye-safe (Class 1) infrared laser based prototype developed < USD $4,000
Size of a typical shoe box: L x B x H =12”x 6”x 6” Weight < 3 lbs.
Actual product design can further reduce size & weight considerably
Custom laser rangefinder design uses special optics to transform the elliptical
laser beam into a thin sheet of laser light (fan shape)
Field interface to Traffic Management Center can be integrated
All weather performance needs to be tested
Mounted on a traditional camera enclosure bracket- simple installation
Uses a standard 12” warning traffic signal for higher visibility
- Flash rate set as per MUTCD
Operational parameters configured through a PC – Serial interface
Requires one time on-site calibration
Single Lane design, Meets “Performance features” of existing OHVDs
“Direction discerning” feature not implemented
“Additional features” of existing OHVDs can be implemented
New York State: Number of Bridge Hits between 1993-2011
Performance Feature
Value
Operating Speed
1-75 mph
Maximum Range (across road width)
200 feet
Minimum size of detected object
¼-4 inch (2 inch)
Alarm/Sign Interface
1-2
False Positives
Minimum
Direction Discerning
Dual Beam Type
Additional Features
Fail Safe Mode
Default Warning Sign Activation
Fault reporting
Power Failure, Beam or Sensor Failure, Beam obstruction
Remote Management
Interface to TMC, event recorder
Vehicle Detector
Road loops to eliminate false positives
8 ft.
Collimated Laser Beam at Detector (left) &
at distance of 8 Ft. (Right), 2 cm thickness
Triangular laser sheet, 7.2 cm wide @ 8 Ft.
(left edge, center, right edge), 2 cm thick
Power
Serial Port
110 V AC /
Traffic Signal
Test Signals
Oblique views of the LaRa detector
 LaRa LRF Range Testing & Target characteristics
 Optical Testing to validate Laser Beam Shape
12 V DC Switches
Front view (left) and Back view (right) of LaRa detector
Economical from DOT perspective
Limited effectiveness
Active
In-cab proximity alerts (GPS/CB Radio)
Use commercial GPS for trucks/CMVs
Utilize DOT oversize permit, escort vehicle services
Use authorized truck route maps
ECR
Real-time truck routing mobile apps
Alteration of structure height through raising the
bridge/overpass or Grinding the roadway surface
Detection and re-routing using over height vehicle
detection (OHVDs) sensors and VMS warning signs
Laser Beam
Propagation
Design
Measured Beam Size at Field Distance
Axis
Divergence Divergence
(645 feet @ 65 mph)
(θ)
(θ)
Design
Measured
Divergence
Divergence
mrad
mrad
Inches
Inches
Fast Axis
0.2
1.085
2.5
9.16
(Vertical)
Slow Axis
178.8
157.86
23.04
20.28
(Horizontal)
(14.9 Ft.)
(13.15 Ft.)
LaRa OHVD: Top View of Installation
 Uniqueness in Operation
 First OHVDS which can be mounted on the bridge being protected
(or overhead gantry/roadside infrastructure).
 Long range detection (>1000 feet). Detect incoming over height vehicle at safe
stopping distance (570 feet @ 60 mph, Level Grade AASHTO)
 Broad detection zones instead of single optical beam for sure detection.
 Eye safe, infrared laser rangefinder based device.
 Uses a standard freeway sized warning sign with flashing yellow beacons,
installed on the bridge face next to the detector.
 Meet or exceed current OHVDS performance specifications
 Vehicle detection algorithms minimize false detections
 Minimal System Cost including Detector, Warning Sign, Signals & Installation
 Line of Sight Warning Sign and Traffic Signal design
 Drivers can always see the warning sign
 No need for expensive VMS/Matrix signs
 Provide Over-Height measurement
 Useful statistic for crash/damage assessment
 Collision Prediction by Speed Measurement
 Pre-emptive Emergency Response & Recovery
 Controlled Damage due to driver response
An artist’s rendition of LaRa-OHVDs installation
8. TESTING & RESULTS
Traffic Signal & Detector Test Set Up
Roadway
Region 10
LaRa- OHVD : Laser Ranging Over-Height Vehicle Detector
Source: Trigg Industries Product Catalog
7. LaRa-OHVD PROTOTYPE




Structure
Region 8
Effectiveness /Challenges
Developing a new regulation
Driver compliance and awareness is
required
Most challenging to enforce
Costly to implement, Vehicle/cargo
damage or driver injury may result in
liability issues
Effectiveness /Challenges
Commercial GPS costly for
fleet/truck owners
Permit process requires planning
TimeSSC
consuming, enforcement?
Low clearance database validity
100 % effective to eliminate hits
Most Cost Prohibitive Solution
Practical & expensive solution
Highly effective in reducing hits
5. LaRa-OHVDs
LIMITATIONS
 Systems installed at greater distance before the bridge; up to a quarter mile
 Power & communication lines may have to be brought up to the installation site.
 Systems require a communication cable between the transmitter and receiver units. Requires digging a
trench across the road width. Results in additional roadway closures & traffic delays.
 Structural & Installation costs usually much higher than system costs
 ITS grade installation $50,000 -$100,000 per approach
 Stand alone detector-pair cost is also expensive
 $9000-$25,000 per approach (Trigg Industries)
 Installed only at critical locations because of very high costs (entrance ramps).
 Suffer from false detections due to snow deposits on vehicle, antennas, flying debris or birds.
 Suffer from alignment issues due to ground heave.
 Most times, drivers miss the only warning sign. Some do not hear the alarm bell (while listening to
radios, etc.) There is no further line of sight signage to stop them from hitting the bridge.
 Some OHVDS use expensive VMS/matrix signs ($20,000-$70,000)
Target
Driver
April 13, 2015, $1/month
4. STATE OF PRACTICE OHVDs
 Introduced in 1965, proven effective in reducing hits, used by 15 State DOTS (2011)
 Consist of pair of aligned optical transmitter-receiver (A), Alarm bell (B) and VMS sign (C)
 Improvements to basic set up have been limited to:
 Modifications in the light source (visible/red/Infrared/laser)
 Light modulation (visible), Operation Mode: diffuse, reflective or opposed (infrared)
 Using single, dual beam or Z-beam systems
Passive
Driver education on bridge hits
Testing on CMV license exams
Vehicle height signs in cabin
Measuring height of cargo before trip
Structure Protection through in-line barriers
(Hanging rods, chains)
Sacrificial beams or Bash bars on or before
the structure
Roadway Efficient posting of over-height warning signs
Markings on roadway and structure
Provide better lighting conditions
Beam Size at
Test Distance
(220 feet @ 30
mph)
Measured
Divergence
Inches
3.65
54.33
(4.53 Ft.)
 Beam Resolution
 @120 Ft (20 mph): 2.36 inch x 2.5 Ft wide
 @ 220 Ft (30 mph): 3.65 inch x 4.5 Ft wide
 Finer focusing of optics can correct beam
shape at field distances.
 Range limitations due to APD receiver design
 Height Resolution in Centimeters
 Vehicle / False Detection Algorithms :
 Currently Under Development
Proposed Warning Sign with Signals
Detection Concept (Regular Height Vehicle)
Detection Concept (Over-Height Vehicle)
9. CONCLUSIONS
 By combining a mature vehicle detection technology (LADAR), special optics and existing traffic
engineering guidelines; a cost effective Laser Ranging Over-Height Vehicle Detector is developed.
 Represents a new sensor innovation in over-height detection in decades.
 Current OHVDs lack market competition, with archaic operation resulting in very high sensor and
deployment cost. Find limited use at most problematic locations.
 Thousands of low clearance bridges & overpasses still vulnerable to over-height vehicle hits.
 LaRa-OHVD is envisioned to detect over-height tractor trailers and large trucks which cause the
maximum number of bridge hits (94 %) in New York State.
 With respect to New York State, majority (78%) of bridge hits have been found to occur on
Parkways, State Highways and Interstates; where the LaRa detector can be utilized.
 Actual field testing is required to validate the system utility and note performance limitations.
 The low cost design, minimal installation, features like broad vehicle detection zones, algorithms
to minimize false detections, line of sight warning sign, collision prediction & over height
measurement; makes the LaRa OHVD an innovative concept in over height detection.
 LaRa-OHVD has the potential to prevent thousands of bridge strikes; save lives, prevent
congestion, save tax payer’s dollars and contribute to the vital infrastructure preservation goals
in the United States.
ACKNOWLEDGEMENTS
This research is supported by the University Transportation Research Center, Region 2
Applicant Name
University
Academic Discipline
Anticipated Graduation Date
Mailing Address
Telephone
Cellphone
Email
Faculty Advisor
Telephone
Email
Abhishek Singhal
The City University of New York
Ph.D. Candidate in Transportation Engineering
Department of Civil Engineering
Fall 2015
Abhishek Singhal
Graduate Research Assistant,
University Transportation Research Center Region 2
The City College of New York
160 Convent Avenue, Marshak-910
New York, NY, 10031
212-650-8060
347-852-4607
[email protected]
Dr. Camille Kamga
212-650-8087
[email protected]
LaRa-OHVD: An Innovative Over-Height Vehicle Detection System to
Protect our Bridges to Prosperity
Abhishek Singhal, Ph.D. Candidate in Transportation Engineering,
Department of Civil Engineering, The City College of New York
Abstract
Collisions between over-height vehicles and bridges are a serious problem across the world.
Over Height Vehicle Detection Systems (OHVDs) have been routinely utilized by transportation agencies
to protect their bridges and overpasses. However, high system costs have limited their deployment
making thousands of low clearance structures vulnerable to collisions. A new over-height vehicle
detector based on existing laser ranging technology (LADAR) is developed to overcome the cost barrier
while providing enhanced capabilities as compared to the state of practice OHVDs. Currently under
development, the LaRa OHVD has immense potential to reduce the over-height bridge hits and protect
the integrity of our transportation infrastructure.
Introduction
New York City is an excellent example of how bridges transform a city by providing vital links in
its transportation network. The ~ 600, 000 bridges across the United States (including the 17,000 highway
bridges in New York State) shape the backbone of the American transportation infrastructure enabling
connectivity, commerce and economic competitiveness. However, latest data from the National Bridge
Inventory indicates that close to 145,800 bridges (~ 24%) are structurally deficient or functionally
obsolete [1]. With aging infrastructure and increasing gaps in transportation funding, the bridge agencies
2
now require innovative and cost effective measures to protect and extend the service life of existing and
newly constructed bridges and overpasses.
Over-height vehicle impacts to low clearance bridges, tunnels and overpasses cause significant
damages to transportation infrastructure, create safety risks for the driver of the vehicle and other
motorists on the roadways and often result in closure of the bridges for lengthy periods with costly repairs
[2]. Most importantly, severe or repeated hits may result in reduced design life of bridge structure
resulting in untimely and extremely high replacement cost.
Currently, many State DOTs/bridge agencies utilize Over-Height Vehicle Detector systems
(OHVDs) over roadways to detect the erring vehicles en-route to low clearance structures. This
technology while proven in field for many years; is outdated and has many noted limitations as reported
by State DOTs. Current OHVDs lack market competition, with archaic operation resulting in very high
sensor and deployment cost. Due to this, these systems are only used at most problematic locations
leaving thousands of other bridges & overpasses vulnerable to over-height crashes.
This paper presents a new ITS roadway sensor (currently under development) by our research
group to detect over-height vehicles. The Laser Ranging Over Height Vehicle Detector (LaRa-OHVD)
or simply “LaRa” is a new detection concept in over-height sensing which uses LADAR technology to
infer a vehicle’s height. This mature technology finds many applications in transportation namely, in
LADAR speed guns, vehicle profiling and automotive sensors (e.g. adaptive cruise control). LaRa meets
the operating requirements of current OHVDs while providing marked improvement in detector
capabilities with a very low system cost.
The paper starts with a background review defining the problem scope. State of practice OHVDs
are then presented with their operation and noted limitations. This is followed by a description of the
proposed solution, the sensing methodology and the advantages of the proposed detector. The paper
concludes by summarizing key findings and directions for future research.
Background Literature
The Over-Height Vehicle Bridge Hit Problem
Collisions between over-height vehicles and low-clearance bridges & overpasses (hereby referred
as “over-height bridge hits”) are a major problem in USA and the world. It is estimated that in U.S., there
are ~5,000 low clearance bridge hits per year which cause over 100 million dollars’ worth of damage to
public & personal property [3]. Crash data for large trucks indicates that, over-height bridge hits alone
have resulted in approx. 20 fatalities (2003-2013) and 75 injuries (2010-2013) per year respectively. Over
height trucks have resulted in ~13,108 structural damage bridge hits in last four years (2010-2013) [4].
Since there is no national database on over-height crashes including all vehicle types, these numbers paint
a very conservative picture of the magnitude of the problem. More conclusively, a 2011 survey of State
Department of Transportation (DOTs) in U.S. revealed that 68% (30 out of 44 State DOTs) consider
bridge hits to be a significant problem. New York State alone has reported ~200 bridge hits /year with
many bridges being repeatedly hit in last few years [5]. Internationally, Ireland (>180 hits/year), United
Kingdom (>2,000 hits/year) and 14 European Union Member states including Western Australia and East
Japan Railway consider bridge hits to be significant safety risk [6].
Factors contributing to bridge hits include; wide disparities in penalties for over height violations
[7], variance in standard bridge clearances between National and off-National Network, different overheight permit requirements between States, anecdotal reporting of bridge clearances (actual/under3
reporting), driver ignorance regarding vehicle/cargo height, lack of route planning by haulers, use of
consumer grade GPS [5], drivers not following authorized routes [8] and inadequate low clearance
warning signs [9]. In U.S., State DOTs have identified “over-height trucks” as prime cause of bridge hits.
Once an over-height vehicle is en-route towards a low clearance bridge, OHVDs are usually the last line
of defense to prevent the bridge hit from occurring.
State of Practice OHVDs
The typical set up for current OHVDs (Figure 2) consist of an aligned optical transmitter and a
receiver unit mounted on poles (A) on opposite sides of the road at the required detection height. The
transmitter emits a light beam across the road width which is continuously detected by the receiver. As an
over-height vehicle passes through, it obstructs the light beam, which triggers the receiver to activate the
warning sign/VMS (B) and alarm bell (C) to alert the driver. Once an over-height vehicle is detected, the
driver can be instructed (using VMS) to stop or take an exit before the structure. The warning sign/VMS,
alarm bells are typically placed 100-150 feet after the detectors (A). The system is designed to work at
highway speeds (75mph) and is installed much before the structure (up to a quarter mile) to accommodate
approach to suitable exits or to allow a safe stopping distance to the structure.
A review of 16 OHVDs systems from 11 different companies (across U.S., U.K, Canada,
Germany, Australia) revealed that this operational set up is used across the world which is exactly similar
to the first reported OHVDs in 1965 [11]. Improvements to the basic set up have been limited to (i)
modifications in the light source (visible red/Infrared/laser), (ii) light modulation (visible), diffuse,
reflective or opposed mode operation (infrared), (iii) using single, dual beam or Z-beam systems [12].
Figure 2. Detection concept of State of Practice OHVDs [10]
Limitations of State of Practice OHVDs
Since these systems are installed up to a quarter mile before the bridge, many times power &
communication lines have to be brought up to the installation site. A communication cable between the
transmitter and receiver units requires digging a trench across the road leading to roadway closures &
traffic delays [13]. Associated structural & electrical installation costs are usually much higher than
detector costs. ITS grade installation has been reported to cost between $50,000 -$100,000 per approach.
The stand alone cost of detector–pair (A) itself is very high ($9,000-$25,000 per approach). Because of
such high system costs, installations are limited to critical locations. State DOTs have reported these
OHVDs to suffer from alignment issues due to ground heave and false detections due to vehicle antennas,
4
flying debris, birds and snow deposits on vehicle. Rain, snow and sunlight during certain hours of the day
have also been reported to cause false positives [5]. Most times, the drivers miss the only warning sign
(C) while some do not hear the alarm bell (B) (while listening to radios, etc.). There is no further line of
sight signage to stop them from hitting the bridge. Also, utilizing expensive VMS/matrix signs ($20,000$70,000) for regulatory messages adds heavily to the system cost.
Proposed Solution: LaRa- OHVD
The LaRa detector is designed to be installed on the face of the structure (e.g. bridge) being
protected itself. The detector uses a standard freeway sized warning sign with flashing yellow beacons
which are also installed on the bridge face next to the detector. Since most bridges already have power
(street lights), this results in minimal installation cost. LaRa combines LADAR, optics and traffic
engineering principles to detect an incoming over-height vehicle at safe stopping distance from the
bridge. The infra-red laser based device is eye safe and low cost, satisfying the performance requirements
of state of practice OHVDs.
Detection Concept of LaRa- OHVD
The LaRa detector is mounted in the center of the roadway, above the bridge clearance height; on
the bridge face itself, pointing towards the oncoming traffic. The detector transmits a sheet of laser light
covering the road width at a distance greater than the safe stopping distance to the structure. The top view
of the installation is shown in Figure 3.
Figure 3. LaRa –OHVD (Top view)
Figure 4. Vehicle detection zones and height measurement
Pre-defined vehicle detection zones are established before the safe stopping distance to the bridge
and LaRa continuously checks for vehicle presence in these zones using LADAR technology. Once a
vehicle is detected, La Ra measures height from top of vehicle to sensor as shown in Figure 4. If vehicle
height is less than bridge clearance, then LaRa discards the measurement. If the vehicle height is more
than the bridge clearance then the vehicle is detected in the large and over-height detection zones (Figure
5
5). As “Measured height” decreases than “Fixed install height”, the over-height vehicle is confirmed.
LaRa then activates the yellow traffic beacons installed next to the warning sign “OVER HEIGHT
VEHICLE STOP WHEN LIGHTS FLASH” mounted on the bridge itself. As soon as over height vehicle
is detected LaRa can communicate with transportation/emergency agencies through a suitable interface.
Figure 5. LaRa over height detection and proposed driver warning system
Advantages of LaRa- OHVD
LaRa is unique it is operation. It is first OHVDs in the world which is installed on the bridge
being protected and features long range detection (> 1000 feet). It detects vehicles travelling at highway
speeds and provides a broad detection zone instead of single optical beam. Existing OHVDs often utilize
inductive road loops to confirm vehicle presence leading to higher installation/system costs. LaRa
employs vehicle detection zones and algorithms to detect vehicles and minimize false alarms (due to
flying debris, birds), a significant advantage over the beam-break approach used in conventional OHVDs.
The total system cost (including detector, warning sign/beacon, installation) is minimal compared to
conventional OHVDs enabling mass deployment. A unique advantage is the line of sight warning system.
Since the warning sign and traffic beacons are installed on the face of the structure, drivers can always see
them and they are hard to miss. This eliminates the need for expensive VMS/Matrix signs or alarm bells
reducing cost and simplifying installation. LaRa can measure vehicle speed and predict if collision is
imminent. This provides crucial seconds for agencies to plan pre-emptive emergency recovery and
response. Also, LaRa continuously measures the vehicle height in detection zones and can provide a very
useful collision statistic for the responding agencies to assess the legal vehicle over-height. LaRa can also
reduce the level of structural damage for an over speeding driver as he responds to the warning sign and
hits the structure at a reduced speed (while braking).
LaRa –OHVD Prototype Construction
Currently, the device is in its design stage and a prototype is being assembled for testing. Figure
8 shows the prototype and the typical test setup. For demonstration purposes, the warning sign is
excluded and only a single traffic beacon is considered.
6
Figure 8. LaRa-OHVD prototype (Left) and test set-up (Right).
Conclusions
Existing OHVDs are limited in deployment and operational features. By combining a mature
vehicle detection technology (LADAR), state of art optics and existing traffic engineering guidelines; a
cost effective LaRa-OHVDs is proposed. LaRa is envisioned to detect over-height trailers, trucks and
large sized loads which cause the maximum number of bridge hits (94 %) in New York State [5].
Expected limitation is the requirement of a straight approach road up till the safe stopping distance to the
protected bridge. With respect to New York State, majority (78%) of bridge hits have been found to occur
on State Highways, Parkways and Interstates which can provide such site characteristics [5]. With LaRa
OHVD currently under development, actual field testing will be required to validate the system
performance. However, the low cost design, minimal installation and features like broad vehicle detection
zones, algorithms to minimize false detections, line of sight warning sign advantages, speed & over height
measurement; makes the LaRa OHVDs an innovative concept in over height detection. By facilitating
mass deployment, LaRa has the potential to protect thousands of our bridges to prosperity; save lives,
save tax payer’s dollars and contribute to the vital infrastructure preservation goals in the United States.
Bibliography
1. U.S. Department of Transportation, Federal Highway Administration, Bridges and Structures (2015),
Inspection, NBI, Deficient bridges by State and Highway System, Accessed 14th April 14th, 2015
http://www.fhwa.dot.gov/bridge/deficient.cfm
2. Carson, J.L. (2008), Commercial Motor vehicle Size Enforcement. NCHRP Project 20-07, Task 254,
Vehicle Size and Weight Management Technology Transfer and Best Practices. National Cooperative
Highway Research Program, Transportation Research Board
http://onlinepubs.trb.org/onlinepubs/archive/NotesDocs/20-07(254)_SizeEnforcement.pdf Accessed
May 1st, 2013
3. Get the Most Effective Low Clearance Alert System for the US. Low Clearance GPS Data, 2008.
www.lowclearances.com. Accessed May 15th, 2013
4. National Highway Traffic Safety Administration, Fatality Analysis Reporting System,
http://www.nhtsa.gov/FARS Data obtained through special request.
5. Agrawal, A.K., Xu. X. and Chen. Z. (2011), Bridge Vehicle Impact Assessment, Final Report, Project
# C-07-10, University Transportation Research Center, New York State Department of
Transportation, New York. https://www.dot.ny.gov/divisions/engineering/technical-services/trans-rand-d-repository/C_07_10_final%20report.pdf
6. Byrne, A. (2009), Special Topics Report- Railway Bridges in Ireland and Bridge Strike Trends.
Railway Safety Commission, Dublin, Ireland. http://www.rsc.ie/publications/railway-bridges-inireland-bridge-strike-trends/ Accessed Aug 7th, 2013
7
7. Fu, C.C. (2001). Maryland Study, Vehicle Collision with Highway Bridges. Contract No. SP907B1,
Maryland State Highway Administration, The Bridge Engineering Software and Technology Center,
Department of Civil Engineering, University of Maryland.
8. Parkway Truck Restrictions, Parkways Truck Regulations Brochure. (2009), New York City
Department of Transportation.
9. Martin, A. and Mitchell, J. (2004), Measures to Reduce the Frequency of Over-Height Vehicles
Striking Bridges: Final Report, Unpublished Report, PPAD9/100/61, Department of Transport, U.K.
10. Trigg Industries (2013), Detection Concept, Trigg Industries Inc.
http://www.triggindustries.com/overheight-vehicle-detection-systems/application-notes/detectionconcept.html
11. Trigg Industries (2013), About Us, Trigg Industries Overheight Vehicle Detection,
http://www.triggindustries.com/about-us.html
12. Sinfield, J. V. Synthesis Study: Development of an Electronic Detection and Warning System to
Prevent Overheight Vehicles from Impacting Overhead Bridges. Publication FHWA/IN/JTRP2009/30. Joint Transportation Research Program, Indiana Department of Transportation and Purdue
University, West Lafayette, Indiana, 2010. doi: 10.5703/1288284314276.
13. Trigg Industries (2013), Z-Pattern Design Notes, Trigg Industries Inc.
http://www.triggindustries.com/overheight-vehicle-detection-systems/application-notes/z-patternrdesign-notes.html
8