Independent Analysis of I-10 Bridge Project and of Alternatives

Transcription

Independent Analysis of I-10 Bridge Project and
of Alternatives
Mobile, Alabama
Prepared for:
Keep Mobile Moving
Prepared by:
14 February 2007
3090 Premiere Parkway • Suite 200 • Duluth, Georgia 30097 • (770) 813-0882
TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................ 1
2. DATA COLLECTION.......................................................................................................... 2
Volume, Speed, and Classification Counts........................................................ 2
License Plate Surveys.............................................................................................. 5
3. DATA ANALYSIS ................................................................................................................ 8
Capacity................................................................................................................... 8
Traffic Diversions .................................................................................................... 11
Downtown Through Trips...................................................................................... 14
Traffic Volume Projections ................................................................................... 14
4. ADDITIONAL CONSIDERATIONS................................................................................... 17
Truck Routing.......................................................................................................... 17
Seasonality ............................................................................................................. 18
Capacity Issue Associated with ALDOT’s Proposed Bridge Alternative...... 20
New Developments.............................................................................................. 21
5. ALTERNATIVES ................................................................................................................. 22
Regional ITS ............................................................................................................ 22
Cochran-Africatown Freeway and Bridge....................................................... 25
Widen I-65............................................................................................................... 27
Reconstructed I-10 / Wallace Tunnel Approaches......................................... 28
6. WESTERN LOOP .............................................................................................................. 30
7. SUMMARY ....................................................................................................................... 32
GLOSSARY OF TERMS ........................................................................................................ 34
LIST OF APPENDICES .......................................................................................................... 35
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I-10 Bridge Alternatives
Keep Mobile Moving
LIST OF TABLES
Table 1. Volume/Speed/Class Summary......................................................................... 4
Table 2. License Plate Capture Rates.............................................................................. 6
Table 3. Distances and Travel Times............................................................................... 11
LIST OF FIGURES
Figure 1. Data Collection Sites .......................................................................................... 3
Figure 2. Peak Hour Volume and LOS .............................................................................. 9
Figure 3. Daily Traffic Volume and LOS - 2005 .............................................................. 10
Figure 4. Highway Travel Paths........................................................................................ 13
Figure 5. AADT / LOS – 2030 (New Bridge) .................................................................... 15
Figure 6. AADT / LOS – 2030 Proposed Improvements................................................ 16
Figure 7. Wallace Tunnel Daily Volume ......................................................................... 19
Figure 8. Wallace Tunnel Weekday Volume................................................................. 19
Figure 9. Regional ITS Solution ......................................................................................... 24
Figure 10. Cochran-Africatown Freeway Solution....................................................... 26
Figure 11. Wallace Tunnel Solution ................................................................................. 29
Figure 12. Western Loop Solution.................................................................................... 31
Editors Note:
Street Smarts, Inc. is an Atlanta-based firm that provides transportation planning,
traffic engineering, roadway and site design services to clients across the Nation.
The company specializes in finding solutions to complex transportation problems
through consensus building. A corporate resume with a listing of representative
projects is included in Appendix C.
I:\1500\1549-02 Keep Mobile Moving\Report\FINAL Report - 07-0214.doc
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1. INTRODUCTION
This report presents an evaluation of alternatives that address the current and
future needs to move vehicles safely and efficiently in and through Mobile, AL. It
documents assorted data collection efforts, analysis methodologies, and
alternative solutions to the I-10 Bridge project currently under consideration by
the Alabama Department of Transportation (ALDOT). It also presents a phased
package of improvements to expand and better utilize existing roadway
capacity around Mobile and across the Mobile River. The elements of the
package include: an Intelligent Transportation System (ITS), select roadway and
Wallace Tunnel improvements and additions, and, perhaps eventually, a new
western by-pass freeway.
The sections that follow will discuss:
•
•
•
•
Current traffic conditions
Future traffic demands
The role of freight demand, and
Proposed solutions.
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2. DATA COLLECTION
There were two types of data collection activities: primary and secondary. The
primary data collection included volume, speed, and classification counts, as
well as license plate origin-destination surveys. The secondary data collection
was based on travel time runs, transportation models, freight studies, and other
documents provided by ALDOT, their consultants, and other transportation and
planning agencies.
The purpose of the data collection effort was to support the analysis tasks which
are documented later in this report. In each step of the process, conservative
assumptions were made which underestimated the results. This was done so that
the recommendations would be based on a realistic and achievable
foundation.
Volume, Speed, and Classification Counts
Rubber tube counters were placed at locations determined to be key freeway
and major highway segments. The counts were collected for 24 hours and
recorded in 15-minute increments; the time periods included the time of the
license plate survey. The counts included classification of traffic into the 13
vehicle types, as defined by the Federal Highway Administration. The counters
also recorded speed information by vehicle type. The detailed traffic volumes
are included in Appendix A but a summary of the volumes appears in Table 1.
The highlighted volumes are those that are of most significance in the traffic
analyses that follow. Figure 1 shows the location of the traffic counts and the
license plate study.
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Legend
INTERSTATE
License plate study location
Saraland
65
nnel
d Tu
khea
Ban
nel
Tun
ace
Wall
43
158
Lee
St
42
5
Rd
Telegraph
1
17
24-hr machine classification count,
Bi-directional
4
Mof
fett
Rd
45
Mobile
Regional
Airport
11
13
Chickasaw
12
Prichard
Cochran Bridge
I-165 Manual License
Plate
3 2
INTERSTATE
165
6
4
INTERSTATE
65
56
Airport Blvd
8
G
t
ov ’
Spanish Fort
2
d
Blv
31
INTERSTATE
INTERSTATE
9
Schillinger Rd
11
1
10
10
1
90
5
Tillmans
Corner
10
INTERSTATE
10
Riviere Du Chien Rd
(Overpass)
Mobile
Bay
Daphne
98
Theodore
NORTH
3090 Premiere Pkwy Suite 200
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
Data Collection Sites
Mobile,
FigureAL
1
Table 1. Volume/Speed/Class Summary
Site
1
2
3
4
Location
I-10, east of US 98 Daphne
Interchange
Direction
EB
WB
US 98, south of I-10, near
Battleship Park
Both
EB
WB
Bay Bridge Road, south of
Cochran Bridge
Both
NB
SB
Both
I-165, north of Beauregard Rd NB
SB
I-65, north of I-165
Both
NB
SB
SR 42, west of I-65
Both
EB
WB
Airport Blvd at I-65
Both
EB
WB
US 90, west of I-65
Both
EB
WB
I-10, west of I-65
Both
EB
WB
5
6
8
9
10
11
12
US 98, east entry into
Bankhead Tunnel
Both
Water St ramps to/from I-10, at EB
WB
Wallace Tunnel
I-10, east of Water St ramps
13
Both
EB
WB
Both
EB
WB
Both
Daily
Volume
21,849
20,566
Daily
Trucks
3,213
2,893
Daily %
Trucks
14.7%
14.1%
Pk Hr Pk Hr
Vol
Trucks
2,160
1,488
42,415
6,106
14.4%
2,740
11,526
8,244
450
174
3.9%
2.1%
1,673
591
19,770
624
3.2%
2,264
5,828
5,006
777
607
13.3%
12.1%
494
545
10,834
1,384
12.8%
1,039
12,094
12,710
748
560
6.2%
4.4%
1,545
651
24,804
1,308
5.3%
2,196
29,929
27,653
3,073
2,790
10.3%
10.1%
2,960
2,087
57,582
5,863
10.2%
5,047
19,473
19,291
997
866
5.1%
4.5%
1,152
2,072
38,764
1,863
4.8%
3,224
28,378
27,281
195
392
0.7%
1.4%
2,040
2,387
55,659
587
1.1%
4,427
14,448
14,964
90
120
0.6%
0.8%
935
1,641
29,412
210
0.7%
2,576
44,544
45,095
4,197
3,016
9.4%
6.7%
3,332
4,726
89,639
7,213
8.0%
2,740
7,429
8,144
160
9
2.2%
0.1%
1,041
588
15,573
169
1.1%
1,629
4,937
3,741
224
172
4.5%
4.6%
560
241
8,678
396
4.6%
801
27,376
25,930
2,752
2,618
10.1%
10.1%
1,817
2,029
53,306
5,370
10.1%
4,774
200
Pk Hr %
Trucks
Avg Pk Hr
Speed
73
61
7.3%
n/a
n/a
63
67
66
64
6.2%
67
54
63
64
2.9%
58
77
84
290
5.7%
80
52
50
n/a
n/a
51
44
42
n/a
n/a
43
51
47
n/a
n/a
49
79
80
200
7.3%
79
34
30
n/a
n/a
31
30
48
n/a
n/a
38
54
59
234
4.9%
*Note: No site 7. Site 12 shows only Water St ramp traffic leaving and entering tunnel
Highlighted locations are the primary study routes
4
67
62
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57
License Plate Surveys
License plates surveys were conducted to determine travel patterns in and
through the area by examining the origins and destinations of the traffic. The
study area was defined by travel routes from I-10 in Daphne, I-10 west of I-65,
and I-65 north of I-165. In general, the study sought to understand the travel
paths among points on I-10, Bay Bridge Road (Cochran-Africatown Bridge), I-165,
and I-65.
The origin and destination data were collected in one direction: from the east to
the west and north. This was due to time and cost constraints as well as on-going
construction, however, in most travel demand modeling, this method is
commonly applied since it is assumed that reverse patterns are similar.
The study locations were chosen because they are on likely paths that drivers
would take if the paths were well-known or if, through signage or other means,
they were directed to a particular path. For example, if there were congestion in
the westbound portion of I-10, approaching the Wallace Tunnel, a variable
message sign could direct traffic to the Cochran-Africatown Bridge, I-165, I-65,
and then back to I-10. Similarly, traffic coming from the north on I-65 could avoid
the Tunnel altogether by being routed directly to the Cochran-Africatown
Bridge, Bay Bridge Road and then to I-10 to the east rather than traveling I-65 to
I-10 and then through the Wallace Tunnel.
To understand the traffic that is candidate for rerouting, license plates were
captured at the I-10/Daphne exit, on the approach to the Cochran-Africatown
Bridge, on I-65 north of I-165, and on I-10 west of I-65. Figure 1 shows the location
of the license plate studies.
An automated system developed to collect license tags using high-speed
cameras and character recognition software was employed. Cameras were set
up at four of the five locations and captured both the license tags and a photo
image of each license plate.
Due to the time of year and the need to capture tags during daylight hours, the
study period was scheduled for 6:30 a.m. to 6:00 p.m., on Tuesday, October 24,
2006. During the morning of the data collection, an accident closed the
westbound Wallace Tunnel for two hours. The license plate capture was
suspended. The afternoon of October 24 and the morning of October 25
became the data collection time periods that represented “normal” traffic
condition.
Post-Processing. While the license plate data were captured digitally at four
locations, the system was unable to capture 100% of the tags. Some conditions
such as the angle of the camera, vehicles following too closely, or plates in nontraditional locations limited the data capture rates. Camera functionality also
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contributed to a reduced capture rate. Table 2 shows the license plate capture
rate for each site.
Table 2. License Plate Capture Rates
Time
6:00
7:00
8:00
9:00
10:00
11:00
12:00
13:00
14:00
15:00
16:00
17:00
Total:
Site 1
41%
63%
72%
70%
68%
69%
71%
69%
66%
69%
64%
69%
66%
Site 2
20%
58%
46%
55%
48%
50%
26%
27%
20%
28%
46%
58%
39%
Site 4
22%
38%
38%
41%
42%
42%
31%
31%
31%
33%
40%
41%
36%
Site 5
61%
59%
59%
64%
66%
55%
61%
61%
60%
59%
62%
66%
61%
The software that captures the data was able to distinguish 33% of the license
tags automatically. Over 40,000 digital images of license plates were collected
and all of them had to be viewed, verified, changed (if necessary), re-checked,
and recorded. This resulted in a total capture rate of 53% for all sites.
Quality control. Before the data could be used in the analysis presented in this
report, it was important to ensure that they were correct. Initially, a digital photo
of every license plate was viewed and recorded. A simple quality control
method was used to check the corrected license plates. In each data set, one in
every 60 records was examined and checked. If an error was discovered, the
record was corrected and the check interval was cut in half. If more errors were
found, then the interval was again cut in half until no errors were found. The
interval rate was then raised back to 60 and the process was repeated. The end
result is a data set that is as complete and correct as possible.
License Plate Matching. The matching of the license plates is the goal for one
component of the analysis. The license plates were matched using a database
management program that limited the matches to logical travel times between
matches. For example, if the travel time between Site 1 and Site 2 is 15 minutes, a
match between vehicles that were seen two hours apart from one another is
probably not relevant to the study.
A statistically significant sample size was estimated using the traffic volume
collected during the license plate study, with a confidence level of 95% and a
confidence interval of 3%. Time periods where the statistically significant capture
rate was not obtained were not used in this report’s analysis.
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The data were expanded using a method presented in “Evaluation of Roadside
License Plate Data Collection Methods for Origin-Destination Studies”, by Bryan
P. Guy, and Jon D. Fricker, Transportation Research Board, August 2006. The
expanded number of vehicles traveling between two stations is determined by
dividing the matches in the sample by the product of the capture rates.
For example, the volume at Site 1 for one hour is 2,000 vehicles and the capture
volume is 1,000 vehicles (50%). The volume at Site 5 is 4,500 and the capture
volume is 2,700 (60%). If there were 200 matches discovered between Site 1 and
Site 5, the expanded matches would be 200 divided by the product of 50% and
60% (i.e., 0.30). The total expanded matches would be 667, or 33% of the traffic
volume leaving Site 1.
The complete matched record set for Site 1 to Site 2, 4, and 5 are shown in
Appendix B.
Results. One conclusion that can be drawn from the license plate study is
ALDOT’s assertion that about 20% of the traffic that travels I-65 south is bound for
I-10 on the east side of the Mobile Bay, and vice versa, is valid. While the license
plate study showed slightly lower values than 20%, the capture rate at some
locations contributed to the slightly lower number.
Another interesting result is that about 40-50% of the traffic observed on I-10 east
of Mobile traveled through to the west side of Mobile. This appears to be lower
than the 60% through traffic presented in the “Alternatives Screening Evaluation
for the I-10 Mobile River Bridge and Bayway Widening EIS, Mobile and Baldwin
Counties, Alabama and its Appendices”, by Volkert & Associates, (August 2005)
(referred to in this Analysis as “the Alternative Screening Evaluation”, “(Volkert,
2005)” and “the Volkert Evaluation”). Note that different time periods yield
different through traffic percentages. During the peak hours of the day when the
Wallace Tunnel is most likely to be congested, the through traffic is only 30-40% of
the traffic stream.
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3. DATA ANALYSIS
The data collection in this report is intended to present additional information
and insight with respect to Mobile’s transportation needs. As part of this, some
elements of work performed for ALDOT are considered and discussed. Among
the alternatives considered by ALDOT, three of them (5, 6, & 11) included the use
of the Cochran-Africatown Bridge (sometimes referred to in this report as the
“northern bridge path”, “northern bridge route”, or “northern bridge”).
A number of points were made in the Volkert Evaluation which resulted in the
elimination of the three alternatives that included using the northern bridge path.
The portion of the analysis contained in this report presents some elements that
were detailed in the Volkert Evaluation. With the additional information, it is
possible that these alternatives would have remained under consideration.
Capacity
In the explanation of the screening process presented in the Volkert Evaluation,
the first step included the question, “Does a northern route over the Cochrane
Bridge provide additional capacity to the Mobile-Baldwin County I-10 corridor?”
Later in the presentation of the results, for the two alternatives that include the
northern bridge route (Alternatives 5 and 6) the conclusion that the purpose and
need are not met is based their not adding capacity to the I-10 corridor
between Canal Street in Mobile and the US 98/I-10 interchange at Daphne.
While it is true that creating capacity in other parts of the system does not
increase the physical capacity of the Wallace Tunnel route, the shifting of traffic
does have the impact of better utilization of the existing capacity.
Improvements to the tunnel itself (which are discussed in another section of this
report) would result in increasing effective capacity.
Capacity is measured in terms of Levels of Service (LOS). LOS A means free flow
conditions. As the LOS degrades closer to the limit (F), the roadway is more
congested and susceptible to failure if a problem arises.
In the two figures which follow (Figures 2 and 3), one can see the base conditions
for the year 2005. The first is a look at the peak hour conditions while the second
looks at the daily conditions. Both methods are used in determining capacity
consumption, level of service and areas that need improvement.
It should be noted that with the exception of the Wallace Tunnel, all segments of
the highway system shown operate at Level of Service D or better. In most
jurisdictions, LOS D is considered the lowest acceptable condition for most
highways.
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17
INTERSTATE
Lanes
4
6
8
10
12
A
2,310
3,580
4,840
6,110
7,360
Freeway Level of Service
B
C
D
3,840
5,350
6,510
5,930
8,270
10,050
8,020
11,180
13,600
10,110
14,110
17,160
12,200
17,020
20,710
E
7,240
11,180
15,130
19,050
23,000
Lanes
2
4
A
1,940
2,900
Uniterrupted Flow Highway
B
C
D
3,140
4,540
5,870
4,700
6,800
8,810
E
6,670
10,010
65
43
Source: Florida DOT AADT LOS Standards, Urbanized Areas, 2001
158
Rd
Telegraph
42
Mof
I-65 North of Lee Street
DHV (Truck %): 5050 (6)
Number Lanes (LOS): 6 (B)
fett
Rd
45
Cochran Bridge
DHV (Truck %): 1050 (6)
Number Lanes (LOS): 4 (A)
INTERSTATE
165
Mobile
Regional
Airport
I-165 South End
DHV (Truck %): 2200 (3)
I-10 @ US 98 Overpass
DHV (Truck %): 2700 (7)
INTERSTATE
56
Airport Blvd
65
Go
v ’t
d
Blv
31
Schillinger Rd
INTERSTATE
ALDOT Count Station #720
DHV (Truck %): 7700 (7)
INTERSTATE
George C Wallace Tunnel
DHV (Truck %): 7200 (9)
Number Lanes (LOS): 4 (E)
90
INTERSTATE
10
10
10
ALDOT Count Station #718
DHV (Truck %): 7000 (10)
Riviera Du Chien Rd
DHV (Truck %): 8300 (4)
Number Lanes (LOS): 8 (C)
Mobile
Bay
AADT Source: ALDOT MOBILE, AL 2005 Live Traffic Data;
Street Smarts counts collected Oct 2006
DHV – Design Hourly Volume
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
98
NORTH
Peak Hour Volume and LOS
FigureAL
2
Mobile,
17
AADT (Truck %): 44,600 (14)
INTERSTATE
Lanes
4
6
8
10
A
22,000
34,800
47,500
60,200
B
C
D
36,000
52,000
67,200
56,500
81,700
105,800
77,000
111,400
144,300
97,500
141,200
182,600
E
76,500
120,200
163,900
207,600
Lanes
4
A
20,400
Arterial Level of Service
B
C
D
33,000
47,800
61,800
E
70,200
65
43
158
AADT (Truck %): 70,830 (11)
Rd
Telegraph
AADT (Truck %): 66,620 (11)
42
Mof
fett
Rd
AADT (Truck %): 33,510 (9)
Cochran Bridge
AADT (Truck %): 9430 (28)
AADT (Truck %): 74,390 (10)
45
AADT (Truck %): 21,270 (8)
INTERSTATE
165
Mobile
Regional
Airport
AADT (Truck %): 57,340 (15)
Number Lanes (LOS): 4 (D)
AADT (Truck %): 86,470 (9)
AADT (Truck %): 14,590 (7)
INTERSTATE
56
Airport Blvd
65
Go
v ’t
d
Blv
31
INTERSTATE
Schillinger Rd
AADT (Truck %): 85,910 (9)
AADT (Truck %): 55,980 (21)
90
INTERSTATE
10
INTERSTATE
10
10
AADT (Truck %): 66,700 (15)
AADT (Truck %): 66,610 (15)
AADT (Truck %): 75,210 (13)
AADT (Truck %): 84,600 (12)
AADT (Truck %): 84,390 (15)
Mobile
Bay
AADT Source: ALDOT MOBILE, AL 2005 AADT
AADT – Annual Average Daily Traffic
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
98
NORTH
Daily Traffic Volume and LOS - 2005
FigureAL
3
Mobile,
Traffic Diversions
From the Alternatives Screening Evaluation, it appears that the traffic diverted to
the northern bridge is from I-10 only; this traffic would now travel north on I-65,
across the bridge and back to I-10 on the east side of the river. Clearly, these
vehicles would be traveling a longer distance than they would if they were on
relatively straight line path. However, there is candidate traffic from I-65 (from
north of I-165) that would use the northern bridge route but that currently uses
the much longer path of traveling a considerable distance to I-10 to cross the
Mobile River via the Wallace Tunnel. It does not appear that this reduction in
travel was previously evaluated as it is an indirect impact when looking at the
study area (Canal Street to Daphne) described as the purpose for the new
bridge.
The travel distances between various points are shown in Table 3 below based
on measurement points shown in Figure 4. Note that the path from I-65 at I-165 to
I-10 and through the Wallace Tunnel to the east side of the river is almost
identical in length and travel time to the path for I-10 traffic to use the CochranAfricatown Bridge. Since, at present, many people traveling down I-65 destined
for the east side of the Mobile River use I-10, this suggests that the actual
distance is not an impediment to choosing the northern bridge route.
Table 3. Distances and Travel Times
To
I-65, north of I-165, via Bay
Bridge Rd
I-65, north of I-165, via
Water St/I-165
I-65, north of I-165, via I10/I-65
I-10, west of I-65, via I-10
I-10, west of I-65, via Bay
Bridge Rd, I-165, I-65
I-10 east of Wallace tunnel
Distance
Time
7.6
9
11.5
10
17.3
15.5
8.2
7.5
16.7
17
Source: South Alabama Regional Planning Commission, Travel Time Study and AreaWide Congestion Index, Volkert & Assoc, Inc., 2001
The traffic currently traveling from I-65 at I-165 to I-10 on the east side of the river
is traversing a distance of 17.3 miles but would only be traveling 7.4 miles if the
northern bridge route were used. The I-10 path is almost identical, but in reverse.
I-10 through traffic currently going through the Wallace Tunnel travels a total of
7.5 miles but would be traveling 16.7 miles if routed to the north.
To fully evaluate the impact of any alternative that uses the northern bridge, one
should not only examine the I-10 movements, but include the reduction of travel
distance and time for vehicles moving north and south on I-65 (north of I-165
primarily) that are currently traveling all the way to I-10 to cross the river.
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Keep Mobile Moving
These trips via the northern bridge not only reduce vehicle miles, they also
reduce the volumes on I-65 and the section of I-10 from I-65’s southern terminus
through the Wallace Tunnel. This frees up capacity for traffic that would be
better served by using the I-10 tunnel-based path.
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Keep Mobile Moving
17
INTERSTATE
65
43
42
fett
Rd
i
6m .
4.
in
6m
Mof
i.
3 m in .
3m
Rd
Telegraph
158
INTERSTATE
Mobile
Regional
Airport
i
9m
in.
7m
165
3.4
45
9.10 mi.
INTERSTATE
8 min.
56
Airport Blvd
65
Go
v ’t
d
Blv
31
INTERSTATE
INTERSTATE
10
Schillinger Rd
10
90
i.
2m .
2
in
8.
5m
7.
INTERSTATE
10
Mobile
Bay
Source: SARPC, Travel Time Study and Area-Wide Congestion
Index, Oct. 2001
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
98
NORTH
Highway Travel Paths
Travel Time and Distance
FigureAL
4
Mobile,
Downtown Through Trips
Another block of traffic that is contributing to the congestion in the Wallace
Tunnel and a portion of I-10 is the traffic that uses I-165. There are trips on this
route (I-10 through the Wallace Tunnel, via city streets, to and from I-165) that are
not destined for any place in the city but simply pass through. A better
connection and better information would divert many of those trips to the
northern bridge alternative as well.
Traffic Volume Projections
In the Alternatives Screening Evaluation (Volkert, 2005), Table 6 shows the
projected traffic in the Wallace Tunnel in 2030 based on a particular scenario.
The northern bridge alternatives show some reduction (11,000 to 18,000 vehicles
per day) in the Wallace Tunnel from the no-build, but these volumes still do not
include the traffic that could be diverted from I-65. In fact, the only traffic
projected for the Cochran-Africatown Bridge is that of general growth of the
current traffic volumes in the area.
There are two changes in the traffic flow that must be examined to understand
the future scenario. Diverting traffic from I-65 to the Cochran-Africatown Bridge
route would reduce the volumes on the portion of I-65 between I-165 and I-10, as
well as on I-10 east of I-65 through the Wallace Tunnel. The other change that is
suggested would reduce the traffic on I-10 east of I-65 and through the Wallace
Tunnel, but add traffic to I-65 north of I-10, on I-165 and on the existing CochranAfricatown Bridge.
The Volkert Evaluation referenced transportation modeling work performed by
the South Alabama Regional Planning Commission and assumed that about
18,000 vehicles would divert to the Cochran-Africatown Bridge if no new bridge
were built on I-10. (Source: Volkert, 2005, Table 6, pg 19). A policy decision
mandating the routing of truck traffic from I-10 could route traffic along this path.
The changes in traffic patterns with the northern option combined with truck
route regulations would allow the Wallace Tunnel to operate at level of service D
or E. (Additional discussion on truck routing follows in Section 4 of this report.)
Shifting I-65 traffic to the Cochran-Africatown Bridge frees up capacity on the
section between I-165 and I-10. Therefore, some traffic from I-10 west of I-65
could be diverted to this route without the need for immediate widening.
Although these shifts will not eliminate the need for improvements on I-65, they
would free up some capacity in the Wallace Tunnel without accelerating the
need for the road widening.
14
Keep Mobile Moving
Assume new I-10 Bridge; no
additional capacity changes
17
INTERSTATE
Lanes
4
6
8
10
A
22,000
34,800
47,500
60,200
B
C
D
36,000
52,000
67,200
56,500
81,700
105,800
77,000
111,400
144,300
97,500
141,200
182,600
E
76,500
120,200
163,900
207,600
Lanes
4
A
20,400
B
C
D
33,000
47,800
61,800
E
70,200
65
43
Rd
Telegraph
158
42
Mof
fett
Rd
Cochran Bridge
AADT (Truck %): 22,700 (28)
AADT (Truck %): 71,100 (10)
45
INTERSTATE
165
Mobile
Regional
Airport
AADT (Truck %): 48,600 (8)
AADT (Truck %): 104000 (15)
Number Lanes (LOS): 4 (F)
AADT (Truck %): 94,400 (9)
INTERSTATE
56
Airport Blvd
65
Go
v ’t
d
Blv
31
INTERSTATE
Schillinger Rd
AADT (Truck %): 92,300 (9)
90
INTERSTATE
10
INTERSTATE
10
New I-10 Bridge
AADT (Truck %): 63,100 (10)
Number Lanes (LOS): 6 (D)*
AADT (Truck %): 38,800 (5)
*The capacity of the proposed bridge is
reduced to account for steep grades and
truck traffic
AADT (Truck %): 113,900 (13)
AADT (Truck %): 132,800 (15)
Mobile
Bay
Source: 2030 AADT Traffc Volume Projections using MATS
Model provided by SARPC, as report in Alternatives Screening
Evaluation for I-10 Mobile River Bridge, Figure 6°
AADT – Annual Average Daily Traffic
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
10
98
NORTH
AADT / LOS – 2030 (New I-10 Bridge)
FigureAL
5
Mobile,
Assume NO new I-10 Bridge;
limited access freeway via
Cochran Bridge; I-65 improved to
8 lanes where needed; I-10 Bay
Way Bridge widened to 6 lanes
17
INTERSTATE
Lanes
4
6
8
10
A
22,000
34,800
47,500
60,200
B
C
D
36,000
52,000
67,200
56,500
81,700
105,800
77,000
111,400
144,300
97,500
141,200
182,600
E
76,500
120,200
163,900
207,600
Lanes
4
A
20,400
B
C
D
33,000
47,800
61,800
E
70,200
65
43
158
Rd
Telegraph
AADT (Truck %): 89,000 (11)
42
Mof
fett
Rd
Cochran Bridge
AADT (Truck %): 40,600 (28)
AADT (Truck %): 84,000 (10)
45
INTERSTATE
165
Mobile
Regional
Airport
AADT (Truck %): 106,000 (9)
INTERSTATE
56
65
Airport Blvd
Go
v ’t
d
Blv
31
INTERSTATE
Schillinger Rd
AADT (Truck %): 104,000 (9)
INTERSTATE
10
10
AADT (Truck %): 104,000 (15)
AADT (Truck %): 72,900 (15)
90
INTERSTATE
10
AADT (Truck %): 104,000 (12)
Source: 2030 AADT Traffc Volume Projections using MATS
Model provided by SARPC, as report in Alternatives Screening
Evaluation for I-10 Mobile River Bridge, Figure 6°; rerouted
traffic based on travel time, guide signs, and estimated origindestination paths
AADT – Annaul Average Daily Traffic
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
AADT (Truck %): 118,000 (15)
Mobile
Bay
98
NORTH
AADT / LOS – 2030
Proposed Improvements
FigureAL
6
Mobile,
4. ADDITIONAL CONSIDERATIONS
Truck traffic moving along the I-10 corridor is significant and expected to
continue to grow; in fact, there are analyses that indicate that the growth rate
will be higher for truck traffic than for automobile traffic. According to the
National I-10 Freight Corridor Study (May 2003), truck traffic in the Mobile area is
expected to grow over 50% by 2025 but automotive traffic is expected to grow
by only 39% over the same time period.
Not specifically accounted for in the I-10 Corridor projection is the expansion of
the State Docks in Mobile. Currently, the State Docks process about 50,000 TEUs
(truck equivalent units) annually. The new Choctaw Point container port is
expected to add about 250,000 TEUs annually. (Source: Alabama State Port
Authority, 2005) This creates both a challenge and an opportunity that needs to
be analyzed further. At the time of this report and of Volkert’s Evaluation, the
projected destinations, the number of miles traveled, and the mix of rail, truck,
and water-borne (including waterways and short-sea shipments) modes of the
containers traveling to and from the Choctaw Point container port were not
known.
Truck Routing
At present, trucks carrying hazardous materials are prohibited from traveling
through the Wallace and Bankhead Tunnels. Instead, truckers are routed across
the Mobile River via the Cochran-Africatown Bridge. The current hazardous
material truck route on I-10 from the west brings trucks into downtown Mobile via
Water Street. Presumably, some hazardous material trucks currently use I-65
instead of Water Street.
There are communities where trucks are directed along routes that are preferred
even if the travel distances are longer than the more direct route. One example
is I-285 around metropolitan Atlanta. Trucks that do not have an origin or a
destination inside this loop road are required by law to use the loop to pass
around the City. In some cases it can add as much as 35 miles to the trip but it
frees the capacity on the routes inside the loop for local traffic. While Atlanta
experiences some significant congestion, the truck route ordinance has allowed
the highway system to squeeze as much capacity from the highways as possible
and reduce the potential for traffic incidents involving trucks.
Truck traffic moving through the Mobile region could be directed to the northern
bridge route. With the full implementation of an Intelligent Transportation System
(ITS), when there are heavy volumes or congestion due to an incident, the truck
traffic could be routed to the northern bridge. Or, a policy decision could be
made similar to that in Atlanta to direct all trucks without an origin or destination
in the city to use the northern route. The candidate population of trucks currently
observed is approximately 15% or 10,000 trucks per day in 2005 and in 2030 it is
17
Keep Mobile Moving
projected to be over 18,000 trucks per day. Conservatively, it is assumed that
10% of the traffic is non-local truck traffic and therefore would be realistic to reroute.
Based on numerous studies, the trucking industry is generally more concerned
about travel time predictability and reliability than absolute travel time. That
means truckers would rather know how long it takes to get from point A to point
B, and always have the trip take that approximate amount of time, than have
wide variations. In this case, adding 10-15 minutes of travel time would be
insignificant if the route were regularly free-flowing. Note that a significant
portion of the truck trips are long trips on I-10 between New Orleans and
Jacksonville. If a trucker’s trip length is currently over 500 miles, a six to nine mile
diversion is a nominal increase. This compares favorably to the alternative which
is unpredictable, and experiences periodic congestion or closure.
One of the criticisms of the existing Wallace Tunnel is its unpredictability with
regard to travel time. On some days, the Wallace Tunnel can accommodate
82,000 vehicles without any problems. On other days, the volume can be
hindered by incidents in the tunnel and on the approaches. If truck drivers had
more assurance of a “normal” trip pattern, they would be open to being
rerouted to the northern bridge option.
If all trucks without a local origin or destination were rerouted, then the impact
on the Wallace Tunnel would be significant. Not only would 10 to 12% (Source:
The National I-10 Freight Corridor Study, 2003) of the traffic volume through the
Wallace Tunnel be removed, but the potential for overturned trailers, multi-lane
crashes, and other safety problems often associated with trucks and cars (i.e.,
vehicles of very different sizes and operating characteristics) would be greatly
reduced. Trucks also accelerate more slowly and take up more capacity of the
roadway than a passenger vehicle. In roadway design, a truck is equivalent to
about three passenger vehicles. Based on 2005 traffic (ALDOT Traffic Counts),
trucks accounted for almost 10,000 of the over 66,000 vehicles per day going
through the Wallace Tunnel. It is estimated that 8,000 of those trucks could be
rerouted to the Cochran-Africatown Bridge, which currently has excess capacity.
Seasonality
Another factor to consider is the seasonality of the traffic through the region. The
Mobile region is a vacation destination by itself, and it is also a pass-through
point for traffic headed to Gulf Shores and the beaches of the Florida
Panhandle. As one example, the summer months see a marked increase in
traffic volume on the freeways and through the Wallace Tunnel. This seasonal
fluctuation will sometimes result in short-term congestion. Figures 7 and 8 show
that traffic peaks during the college and high school spring breaks and during
the summer months. During those times, the Wallace Tunnel is more likely to
experience congestion.
18
Keep Mobile Moving
If there were a viable alternative to the Wallace Tunnel that could reroute the
seasonal traffic volume, the frequency of congestion could be reduced. Nonfrequent users of the freeway system in Mobile could be directed to the northern
bridge alternative. Route signing, public awareness campaigns, and convenient
paths would help reduce congestion in the Wallace Tunnel.
Figure 7. Wallace Tunnel Daily Volume
Wallace Tunnel
Daily Traffic Volume
80000
70000
60000
Oct-06
Sep-06
Aug-06
Jul-06
Jun-06
May-06
Apr-06
Mar-06
Feb-06
Jan-06
40000
Dec-06
50000
Nov-06
Daily Volume
90000
Source: Compiled from ALDOT Tunnel Traffic Volumes, Mobile, 2006
Looking at just the weekday traffic volumes, the seasonality of the data is further
explored in the next graphic.
Figure 8. Wallace Tunnel Weekday Volume
Wallace Tunnel
Weekday Traffic Volume
80000
70000
60000
Oct-06
Sep-06
Aug-06
Jul-06
Jun-06
May-06
Apr-06
Mar-06
Feb-06
Jan-06
40000
Dec-06
50000
Nov-06
Weekday Volume
90000
Source: Compiled from ALDOT Tunnel Traffic Volumes, Mobile, 2006
19
Keep Mobile Moving
Capacity Issue Associated with ALDOT’s Proposed Bridge Alternative
The proposed bridge over the Mobile River is six lanes wide with an estimated
190’ vertical clearance over the water (Volkert, 2005). Alternates A and B show a
connection to I-10 on the west side of the river just north of Virginia Street
interchange. (Virginia Street is a desirable destination or “touch-down point” for
the new bridge because of the high traffic volume, especially truck volume from
the State Docks that use that interchange.) Alternate C is too far south to be
able to make the connection to Virginia Street without a nearly 7% grade.
The Alternatives Screening Report (Volkert, 2005) stated that the desired
clearance over the Mobile River is 190 feet (est. 215 feet to the bridge deck). For
Alternates A and B to connect to I-10 far enough north of Virginia Street to allow
weaving to and from the interchange, the grade would have to be 4% and 4.3%
respectively. The maximum grade for an Interstate of this type is 3%. (Source:
Geometric Design of Highways and Streets, AASHTO, 2004).
The approach lanes for Alternates A and B would be 4,700 feet and 4,400 feet,
respectively. The effect of a long climb on truck traffic is profound. A truck that
started up a 4,700 foot, 4% grade at 55 mph would be traveling at about 33 MPH
by the time it reached the top. If the slope were 3%, a truck would be traveling
at 48 MPH near the top. (Source: Geometric Design of Highways and Streets,
AASHTO, 2004). Again, this assumes a starting speed of 55 MPH. If the truck were
traveling at a lower speed, the travel speed at the top of the bridge would be
considerably less. A truck entering via a ramp at Virginia Street would have a
lower starting speed.
The AASHTO publication suggests that if the traffic volume exceeds 200 vehicles
per hour, trucks volume exceeds 20 vehicles per hour, and the speed reduction is
greater than 10 MPH, then one should design a "climbing lane". In the case of
the proposed bridge, one of the three lanes would become the truck climbing
lane and would reduce the capacity of the bridge to something much less than
three lanes. The result of a long, steep grade is a de facto truck lane which truck
traffic would use to navigate the bridge, in both the east and westbound
directions.
The Sunshine Skyway bridge in St. Petersburg, FL is an example of a bridge where
one lane is used almost exclusively by trucks because of the long, steep grades.
The Sunshine Skyway Bridge’s approaches are straight, not curved as the three
finalist new Mobile River bridge alternatives are configured. The horizontal
(approach) curves, coupled with the long, steep slope would present an
additional operational issue on the proposed Mobile River bridge that is not
experienced on the Sunshine Skyway Bridge.
If the truck traffic were to consume one lane of the bridge in the uphill
approach, the effect would be a reduction in the overall capacity of the bridge.
Under ideal conditions, the capacity of a 6-lane, interstate bridge would be
20
Keep Mobile Moving
105,800 vehicles per day. However, if one lane is consumed by trucks, the
effective capacity (i.e., LOS D or better) would be about 86,500 vehicles per
day.
By contrast, the Cochran-Africatown Bridge has a relatively short slope at a
maximum approach grade of 4.67%. While this grade may not be ideal for truck
traffic, the 2600 foot slope would mean about an 8 MPH drop in travel speed for
most trucks. The effective capacity is only slightly diminished due to the
approach grade.
New Developments
There are new developments which when open, promise to add significant
traffic volume on the roadways around Mobile. The expansion of the State Docks
at Choctaw Point has already been discussed. According to a study published
by The University of Alabama Huntsville Department of Economic Development,
the predominant flow of traffic from the new container port at Choctaw Point
will be north and south on I-65. (Source: Transportation Infrastructure in Alabama,
UAH, 2005)
According to the same report, the McDuffie Island Coal Terminal has been
informed by the Southern Company that it intends to double the tonnage of
coal imported to serve Alabama’s power needs. Most of this additional tonnage
will be shipped by land via rail but some will be shipped north via I-65.
The new Alabama Motor Sports Park will be located near Pritchard and Saraland
in north Mobile County. It is expected that the new 3,000-acre site will draw
traffic from around the Southeast. Given its location north of Mobile, the most
convenient access will be either I-65 from the north and west or the CochranAfricatown Bridge from the east. The park expects to break ground in late 2007
according to a press release dated December 15, 2006.
US 98 will be rerouted north of the present location to a new alignment between
the Alabama-Mississippi state line and I-65 via the current SR 58. This will bring the
US 98 traffic to I-65, north of I-165. Through traffic, especially trucks, will be able to
travel around Mobile to the north via the Cochran-Africatown bridge without
having to traverse through downtown Mobile and/or the Wallace Tunnel.
21
Keep Mobile Moving
5. ALTERNATIVES
Based on all of the data collected and analyzed, it was determined that there
were opportunities for successful alternative solution implementation of the
alternative solution that would meet the mobility needs but with different
impacts to the local area.
Four design choice elements are described in this report and are intended to
offer alternatives to the proposed I-10 Bridge project that would eliminate, if
implemented in a logical phased manner, the need for a new bridge. The four
alternatives shown graphically and described in the following pages are:
A.
B.
C.
D.
Regional ITS
Cochran-Africatown Freeway and Bridge
Widen I-65
Reconstructed I-10 / Wallace Tunnel Approaches
Regional ITS
The Alabama D.O.T. has been implementing an Intelligent Transportation System
in the Mobile area for a number of years. The existing system is primarily centered
around the Wallace and Bankhead Tunnels and is effective in responding to
incidents in the tunnels. The system includes monitoring cameras, vehicle
detectors, message signs, and communication cables to the devices. The system
is still in its early stages and is scheduled to be expanded in the years to come.
The ITS that is proposed in this report for the interstate highways around Mobile
includes primarily the highways and the Cochran-Africatown Bridge. Once fully
deployed, the system will be able to monitor a larger network of traffic and
provide information to the traveling public so that it can make informed driving
choices.
The system proposed in this report incorporates a regional approach to ITS, one
that would help motorists make decisions well before they end up stuck in traffic.
The system would not only serve Interstates I-10, I-65, and I-165 but could also
serve the major highways like US 90, US 98, Airport Boulevard, and Government
Street. For example, someone coming from Pascagoula would see a sign on I-10
west of I-65 that says the Wallace Tunnel is blocked and he/she may choose to
go north on I-65 and take I-165 and the Cochran-Africatown bridge.
The ITS is not fully funded at this point. It is costly to extend the fiber-optic
backbone and procure and install the many cameras and signs needed to
make the system work. It is estimated that it could cost as much as $40 million to
complete the system – most of which comes through Federal funding
mechanisms.
22
Keep Mobile Moving
The highway portion of the ITS is the most critical part of the plan. Most of the $40
million would be spent on communication and devices for the freeways. About
15% would be spent on non-freeway applications.
Concept:
Est. Cost:
Est. Completion:
Disruption to traffic:
Regional ITS
$40M
2-5 years from start
Negligible
23
Keep Mobile Moving
Saraland
Legend
158
Concept:
Regional Intelligent Transportation
System.
Objective:
Real time re-routing of traffic around
congested areas; improved incident
response; reduced regional
congestion.
Description:
Vehicle detectors for monitoring
speeds on freeways and major
corridors; closed circuit television to
monitor incidents; variable message
signs to advise motorists of
incidents or other public
information.
Est. Cost:
$40 Million
CCTV
Vehicle Detector
INTERSTATE
65
Variable Message Sign
Pritchard
Lee St
W
Chickasaw
le
st
hi
n Ave
t
rS
Wilso
Cochran
Bridge
45
Ave
hard
Pric
98
Transportation
Management Center
INTERSTATE
165
e
Av
Spring
Hill Ave
St
St
ep
he
ns
Old Shell Rd
St
Houston St
Dauphi
n
Rd
Wa
ter
St
t
ss S
e
r
g
n
o
C
Texas St
Airport Blvd
Virginia St
INTERSTATE
an A
ve
Duval St
George C
Wallace
Tunnel
98
Spanish Fort
31
INTERSTATE
INTERSTATE
10
10
Mic
hig
Dauphin Island Pkwy
Go
ve
rn
me
nt
Bl
vd
St
65
Broad
Mobile
Extent of Current
System (2006)
K
ML
d
R
tt
fe
of
M
Bankhead
Tunnel
98
Mobile Bay
90
INTERSTATE
10
Daphne
e
ng
Ra
line
Tillmans Corner
Rd
N
Theodore
North
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
Regional ITS Concept Plan
Note: this includes, but is not limited to
elements already in place or anticipated in
ALDOT’s ITS Master Plan for the area.
(Source: ALDOT Mobile TMC)
Mobile, AL
Cochran-Africatown Freeway and Bridge
The concept behind the enhancements to Bay Bridge Road (renamed
“Cochran-Africatown Freeway”) and the Cochran-Africatown Bridge vary from
the Alternative Screening Evaluation in a significant way. In ALDOT’s evaluation,
the freeway and the bridge would be brought to interstate standards. However,
the goal of making the Cochran-Africatown Bridge an attractive alternative to
the Wallace Tunnel can be accomplished by making a limited access freeway
with lower design speeds – 55 MPH or less. The Cochran-Africatown Bridge is now
signed for 45 MPH and is well traveled by trucks; almost 30% of the volume is
truck traffic.
The Freedom Parkway in Atlanta, Georgia is an example of a limited access
highway that traverses through residential and historic areas at 45 MPH. The road
is designed to move traffic, but in a safe and efficient way. Ronald Reagan
Parkway in Gwinnett County, Georgia is a limited access freeway with a posted
speed of 50 MPH that connects one side of the county with the other. California
mixes Interstate standard freeways with local freeways to provide more localized
access than an Interstate is designed to do. An example is the Pasadena
Freeway in the Los Angeles area.
One of the criticisms of using the Cochran-Africatown Bridge is that the bridge
has both a vertical curve and a horizontal curve on the east side of the bridge.
As discussed previously, the slope is less than 5% and is less than 0.5 miles in
length. However, if necessary, the bridge could be redesigned or even widened
to increase the capacity and efficiency. In fact, if a limited access highway were
built beside the existing Bay Bridge Road, the connection to the CochranAfricatown Bridge would need to be made at a different location than it is
currently.
If it is determined in the future that it is desirable to further grow the capacity of
the northern route, three additional enhancements should be considered:
¾ Improving the existing bridge structure and its connections to the
adjacent roadways, or
¾ Developing a parallel span with appropriate roadway connections, or
¾ Replacing the bridge with a new structure.
The concept shown on the following page provides for a limited access, fourlane freeway connecting I-10 and I-165. There will be interchanges at the termini
as well as key intersections in Prichard.
Concept:
New freeway, new approaches to the CochranAfricatown Bridge
Est. Cost:
$132M
Est. Completion:
Disruption to traffic: Partial closure of Bay Bridge Rd during construction
25
Keep Mobile Moving
d
Paper Mill
p
gra
Rd
le
Te
i dge R
Bay Br
hR
d
INTERSTATE
INTERSTATE
165
165
Bay
Interchanges with Telegraph Rd
for westbound traffic and Paper
Mill Rd for eastbound traffic.
Brid
ge R
Interchange with I-165 for
southbound-to-eastbound
and westbound-tonorthbound traffic.
Includes access to/from
Bay Bridge Road (US 90)
d
Utilize existing CochranAfricatown Bridge (four lanes)
Interchange for Bay Bridge
Rd access to new freeway
Proposed Four-lane
limited access (freeway)
Interchange with I-10 for southbound to
eastbound and westbound-to-northbound
traffic. Requires integration with or
replacement of existing ramps.
Concept:
Limited access highway (freeway) from I-165 to
I-10 along the current Bay Bridge Road (US 90)
alignment.
Objective:
Provide improved alternative route across the Mobile
River.
Description:
Four-lane cross-section, utilizing the existing
Cochran-Africatown Bridge and Bay Bridge Road.
Interchange at I-165, Telegraph Road, Paper Mill
Road, Freeway access road (south of CochranAfricatown Bridge), and I-10.
Estimated Cost:$132 Million
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
e
Tu n n
e
c
a
Wall
l
INTERSTATE
INTERSTATE
165
10
N
North
0 .1 .2 .3 .4 .5miles
APPROX. SCALE
Cochran-Africatown Frwy
(Conceptual Drawing)
Mobile, AL
Widen I-65
I-65 between I-10 and I-165 is expected to experience growth in traffic by 2030
such that the levels of service will approach failing conditions along some
locations. If no improvements are made to I-10 crossing the Mobile River, more
traffic will divert to I-65 and increase the likelihood of congestion. Currently, the
most severe congestion is between Airport Blvd and Springhill Avenue where
interchanges are relatively close to one another.
The section of I-65 between I-10 and I-165 is currently either six or eight lanes wide
(three or four lanes in each direction). While no concept designs have been
developed to accomplish the widening, the median and the shoulder would
have to be improved. However, visual inspection indicates that there is sufficient
room to provide the additional lane in the areas that are not already eight lanes
wide. Some overpass bridges may need to be reconstructed. It should be
noted that the Alternatives Screening Evaluation acknowledges that upgrades
to I-65 between I-165 and I-10 are required to reduce congestion even if traffic
from I-10 is not diverted to I-65. (Volkert, August 2005, p.7)
The Volkert Evaluation examined the costs associated with the reconstruction
and concluded that they would be about $50M. (Source: Alternatives Screening
Evaluation, Appendix F)
Concept:
Est. Cost:
Est. Completion:
Increase to eight lanes between I-10 and I-165
$50M
Minor disruption in flow during construction activities
27
Keep Mobile Moving
Reconstructed I-10 / Wallace Tunnel Approaches
Independent of which alternative is selected, from both a safety and a capacity
perspective, it is well-established that the existing Wallace Tunnel approaches
and exits would benefit from reconfiguration.
The west approach to the Wallace Tunnel has two significant safety and
capacity issues that result in occasional incidents and daily inefficiencies. The first
problem is the extreme horizontal curve for traffic on I-10; traffic traveling in both
directions must make a quick turn as they approach and exit the tunnel. While
this causes motorists to slow down in anticipation of the curve, the curve itself
contributes to poor visibility, sideswipe accidents, and crashes into the freeway
barrier wall.
The second issue on the west approach/exit is the merge point for traffic from
Water Street bound for the Wallace Tunnel and I-10 eastbound traffic. The merge
point occurs only 650 feet west of the Wallace Tunnel, which is a short distance
to merge three lanes of traffic into two. When the Wallace Tunnel and viaducts
were built, the standards and traffic volumes were different. If the Wallace Tunnel
were being built today, the design of the approaches would be much safer.
In the late 1980s and early 1990s, ALDOT developed plans to realign the I-10 west
approaches to the Wallace Tunnel. At the time, the cost estimates were nearly
$50 million; the plans were scratched and the project halted.
The realignment proposed in this report creates a gentler curve approaching the
Wallace Tunnel and moves the merge point for Water Street traffic further away
from the tunnel. The result is a freeway with more capacity and a decreased
chance of crashes as a result of enhanced freeway geometry.
Concept:
Est. Cost:
Est. Completion:
Realigned freeway ramps
$75M
Significant, due to heavy traffic volume and realigned
bridges
28
Keep Mobile Moving
St
te
Wa
nti
Co
r St
St
S
in
ph
u
Da
98
Wa
llac
nel
n
u
eT
INTERSTATE
INTERSTATE
165
10
St
Two lanes into tunnel
Existing merge point for I10 Eastbound traffic and
Water St traffic, 650’ from
tunnel
Three lanes
New merge point 1050’
from tunnel
Lo
op
Fr
om
W
ate
To Water St
rS
t
h
urc
h
C
He
nry
t
rS
S Royal St
to
W
ate
St Emmanuel St
I-1
0
nnel
I-10 to Wallace Tu
I-10 from Wallace Tunnel
Aa
ron
Civic
Center
Canal St
ea
el
t
lS
a
y
Ro
nkh
Ba
unn
dT
INTERSTATE
INTERSTATE
165
10
N
North
Concept:
New I-10 approach to Wallace
Tunnel
Objective:
Improve safety and add capacity to I10 on the west side of Wallace
Tunnel
Description: Reconstruct the I-10 eastbound
approach to the tunnel and move the
connection point from Water St
approx. 400 feet further from the
Wallace Tunnel; Reconstruct
associated ramps and connections to
coincide with approach highway.
Est. Cost:
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
New Eastbound approach to
tunnel to provide safer curve
and easier merge with
downtown traffic – three
lanes merge to two lanes
$75 Million
Wallace Tunnel – West Side
Mobile, AL
6. WESTERN LOOP
The Western Loop has been in the planning stages for many years. The South
Alabama Regional Planning Commission (SARPC) has included it in their long
range plans. The project became controversial and was removed from ALDOT’s
work program. However, the SARPC feels that this project is significant to the
region and has continued to support it in their long range planning.
The SARPC plan includes a four-lane highway that would connect I-10 on the
south with the new US 98 / SR 158 improved highway to the north. The concept
presented in this study creates a north-south portion of that highway on the west
side of the Mobile Regional Airport and then turns toward the east and intersects
I-65, north of I-165. (See Figure 12)
The Western Loop, while an important regional highway in its own right, is in
addition to the solution package presented in this report. In addition to providing
an alternative route to I-65 and I-10 between the Loop’s north and south termini,
it would offer much needed relief to Airport Boulevard and provide freeway
access to the Mobile Regional Airport.
Concept:
Est. Cost:
Est. Completion:
New limited access highway
$163M
Isolated areas of disruption in the less rural parts of the
county
30
Keep Mobile Moving
INTERSTATE
INTERSTATE
165
65
W Lee St
98
INTERSTATE
INTERSTATE
165
165
42
Prop
o
Snow R
d
sed W
er Rd
Schilling
M
sR
ob
ile
Bridge over
lowland/wetland areas
Rd
d
R
eg
io
na
New airport exit at
Tanner Williams Rd
lA
irp
o
rt
Concept:
Limited access highway
(freeway) from I-10 to I-65, west
of Mobile Regional Airport,
along primarily undeveloped
land
Objective:
Provide a loop freeway to relieve
I-65 between I-165 and I-10;
provide freeway access to
Mobile Regional Airport from I10 and I-65
d
Blv
t
r
rpo
n
ilto
am
H
ff
Je
Rd
sR
e
w
Da
New Airport Blvd exit
for airport bound traffic
Description: Four-lane cross section, 26.8 mi
freeway, utilizing new alignment
with interchanges at I-10, Jeff
Hamilton Mill Rd, Airport Blvd,
Tanner Williams Rd, Howells
Ferry Rd, US 98, and I-65
d
Est. Cost:
$163 Million
New interchange with
I-10 8 miles west of I-65
CR 39
ester
n
Loop
lls
we
Ho
Ferry
TannerWilliam
Ai
New interchange
with I-65, 5 miles
north of I-165
d
Ol
u la
o
g
ca
s
Pa
Rd
INTERSTATE
INTERSTATE
165
10
Duluth, GA 30097
770.813.0882
770.813.0688 (fax)
www.streetsmarts.us
N
0 .5 1 1.5 2miles
North
APPROX. SCALE
Western Loop
Mobile County, AL
7. SUMMARY
The current bridge options proposed by ALDOT fit the criteria used in their
evaluation. Other solutions provide much of the same traffic relief but with a
lower cost and a faster implementation schedule. The solution presented in this
report, when fully implemented, produces capacity needed for the future.
An integral part of the solution is an Intelligent Transportation System (ITS).
Regional deployment of monitoring cameras, detectors, variable message signs,
and the communication infrastructure needed to support the ITS will help reroute
traffic around congested areas.
Another element in the Alternative Solution package is the northern bridge
component that includes a limited access freeway between I-10 and I-165.
Besides providing another freeway crossing of the Mobile River, the northern
bridge is also a useful alternative if truck traffic were, by policy, diverted around
the City of Mobile rather than going through the Wallace Tunnel and, in the case
of trucks carrying hazardous material, through downtown.
The proposed components could be implemented simultaneously or sequentially
and funding is likely to be the determinant. Construction of some components
can overlap others without creating cascading congestion spots in the highway
system. For example, the ITS component consists of an on-going implementation
of fiber-optic cable, CCTV, detectors, and variable message boards. The
Cochran-Africatown Freeway component would be built primarily outside the
current roadway right-of-way and would therefore have minimal impact on
traffic.
The following shows a comparison between the ALDOT-proposed project and
the alternative solution package presented in this report.
ALDOT Proposed Project
Alternative Solutions
New I-10 bridge over Mobile River ($363M)
Widen the I-10 Bayway ($240M)
Widen I-65 between I-10 and I-165 ($50M)
Expand regional ITS ($40M)
Cochran-Africatown Freeway ($132M)
Prohibit through trucks in Wallace Tunnel
Widen the I-10 Bayway ($240M)
Widen I-65 between I-10 and I-165 ($50M)
The ALDOT Proposed Project is expected to cost $653M in 2005 dollars based on
the Alternative Screening Evaluation. The solution offered in this report is
projected to cost $462M, based on unit cost assumptions from the Volkert
Evaluation and industry standards for ITS costs. If funds were available at the
time needed, a new I-10 bridge could take as long as seven years to fully plan,
design, and do right-of-way acquisition, then three years to construct. Two years
have already passed in the estimated ten-year process.
32
Keep Mobile Moving
A Regional ITS could take two years to design and construct if funds were
available. The Cochran-Africatown Bridge is available and underutilized now
and has the capacity to move traffic. The time to plan, design and complete
the Bay Bridge Road enhancements could be eight to ten years. However, the
new Cochran-Africatown Freeway could be built while traffic is routed to the
Cochran-Africatown Bridge via Bay Bridge Road. Since there is existing usable
capacity, motorists would not have to wait for construction to be completed to
begin reaping the benefits of the northern bridge option. Rerouting throughtrucks around Mobile is a policy decision that could be implemented at any time
when proper signage or ITS is installed. All other aspects of the Volkert Evaluation
and StreetSmarts’ Report are essentially the same. With an average inflation rate
of three percent (3%) per year, the time to complete each element described
above, and an estimated completion date of 2015, the cost to complete the
alternative solution is approximately $266M less than the ALDOT Proposed
Project, in 2015 dollars.
There are additional components that would enhance the regional
transportation system. Fixing the western approach to the Wallace Tunnel will
have a significant impact on the capacity of I-10 at the tunnel. The Western
Loop will serve the region by providing another north-south freeway on the west
side of the county and a new east-west freeway, north of the Mobile Regional
Airport.
The proposed I-10 bridge project has other potential impacts that are not
discussed in this report. There are likely maritime impacts, cultural and historical
impacts, national security concerns, and aesthetics that need to be fully
explored before a decision on the proposed project is made. These issues will
need to be considered for the Alternative Solutions presented in this study and
compared to the ALDOT proposed I-10 bridge.
33
Keep Mobile Moving
GLOSSARY OF TERMS
Intelligent Transportation Systems (ITS) – the management of traffic through the
use of monitoring equipment and other information gathering and dissemination
techniques.
Classification Counts – traffic volume counts that segregate the counts into 16
vehicle types such as automobile, bus, RV, 18-wheelers, etc.
License Plate Study – the capture of license plates at two or more locations for
the purposes of determining the origin, destination and path of traffic
Freeway – a roadway with controlled access points.
Interstate – a freeway designated in the U.S. Interstate System. Design standards
are established by the Federal Highway Administration (FHWA)
Level of Service (LOS) – a grading system of roadway performance; LOS A is
characterized by free-flow conditions; LOS F is typically the heaviest congestion
level.
Truck Equivalent Unit (TEU) – volume measurement of freight hauled by truck, rail,
ship, barge, etc. For example, one container is one TEU whether it is transported
by rail or truck.
Truck Equivalency Factor – typically equal to three passenger cars
34
Keep Mobile Moving
LIST OF APPENDICES
The following represents the information that can be found in the appendices to
this report.
•
Appendix A – Traffic volume, speed, and vehicle classification counts
•
Appendix B – Summary results of license plate study
•
Appendix C – Street Smarts firm information
Copies of the appendices can be obtained by contacting Keep Mobile Moving,
c/o Samantha Johnston, 251-431-8021.
35
Keep Mobile Moving

Independent Analysis of I-10 Bridge Project and of Alternatives

Transcription

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