Experience planning, installing, and evaluating pilot Variable Speed Limit (VSL) systems in Texas.
San Antonio, Texas, United States
Temple, Texas, United States
Texas, United States
In 2014, acting on a ruling by the Texas Transportation Commission, TxDOT and Texas A&M Transportation Institute (TTI) a Variable Speed Limit (VSL) pilot program was implemented. The pilot program aimed to study the effectiveness of temporarily lowering speed limits to address inclement weather, congestion, road construction, and other factors that can affect the safe and orderly movement of freeway traffic.
The VSL systems were implemented in the summer of 2014 to assess performance under a variety of operational conditions:
- Urban Congestion Site: San Antonio, SL 1604SL 1604 WB, US 281 to IH-10. Data collected from June 30, 2014 – December 31, 2014.
- Construction Work Zone Site: Temple, IH-35 NB, MM 297 to MM 301. Data collected from June 23, 2014 – November 30, 2014.
- Weather-Related Site: Ranger Hill, Eastland County, IH-20 EB and WB. Data collected from July 21, 2014 – January 30, 2015.
The project team developed detailed cost estimates at each deployment site. Costs estimates covered Portable Changeable Message Sign (PCMS) rentals and modifications required to integrated equipment to the PCMS, radar sensors, visibility sensors, roadway condition sensors, modems, and other miscellaneous equipment. All of these costs were calculated with indirect costs applied where assumed.
Total Equipment Initial Cost Estimate
Site |
Direction
|
Site Cost ($)
|
---|---|---|
San Antonio |
WB
|
180,487
|
Temple |
NB
|
116,187
|
Ranger Hill, Eastland County |
EB
|
108,503
|
Ranger Hill, Eastland County |
WB
|
91,464
|
Total Equipment Cost |
496,641
|
Initial Cost Estimates for WB SL 1604 VSL Site, San Antonio.
Equipment |
Quantity
|
Payment Unit
|
Unit Cost ($)
|
Monthly Cost ($)
|
Total Cost($)
|
---|---|---|---|---|---|
Reduced Speed Ahead PCMS |
1
|
Monthly
|
3,227
|
3,227
|
12,908
|
VSL PCMS—Base |
8
|
Monthly
|
2,708
|
21,664
|
86,656
|
VSL PCMS—Modifications |
8
|
Monthly
|
519
|
4,152
|
16,608
|
Vehicle Detector |
8
|
Each
|
5,500
|
N/A
|
44,000
|
Roadway Visibility Sensor |
0
|
Each
|
5,224
|
N/A
|
–
|
Roadway Condition Sensor |
1
|
Each
|
11,315
|
N/A
|
11,315
|
Vehicle Detector Modem |
8
|
Each
|
500
|
N/A
|
4,000
|
Miscellaneous |
1
|
Each
|
5,000
|
N/A
|
5,000
|
Total Equipment Costs |
$180,487
|
Initial Cost Estimates for NB IH-35 VSL Site, Temple.
Equipment |
Quantity
|
Payment Unit
|
Unit Cost ($)
|
Monthly Cost ($)
|
Total Cost($)
|
---|---|---|---|---|---|
Reduced Speed Ahead PCMS |
1
|
Monthly
|
2,708
|
2,708
|
10,832
|
VSL PCMS—Base |
5
|
Monthly
|
2,708
|
13,540
|
54,160
|
VSL PCMS—Modifications |
5
|
Monthly
|
519
|
2,595
|
10,380
|
Vehicle Detector |
4
|
Each
|
5,500
|
N/A
|
22,000
|
Roadway Visibility Sensor |
0
|
Each
|
5,224
|
N/A
|
–
|
Roadway Condition Sensor |
1
|
Each
|
11,315
|
N/A
|
11,315
|
Vehicle Detector Modem |
5
|
Each
|
500
|
N/A
|
2,500
|
Miscellaneous |
1
|
Each
|
5,000
|
N/A
|
5,000
|
Total Equipment Costs |
$116,187
|
Initial Cost Estimates for EB IH-20 VSL Site, Ranger Hill, Eastland County.
Equipment |
Quantity
|
Payment Unit
|
Unit Cost ($)
|
Monthly Cost ($)
|
Total Cost($)
|
---|---|---|---|---|---|
Reduced Speed Ahead PCMS |
1
|
Monthly
|
2,708
|
2,708
|
10,832
|
VSL PCMS—Base |
4
|
Monthly
|
2,708
|
10,832
|
43,328
|
VSL PCMS—Modifications |
4
|
Monthly
|
519
|
2,076
|
8,304
|
Vehicle Detector |
4
|
Each
|
5,500
|
N/A
|
22,000
|
Roadway Visibility Sensor |
1
|
Each
|
5,224
|
N/A
|
5,224
|
Roadway Condition Sensor |
1
|
Each
|
11,315
|
N/A
|
11,315
|
Vehicle Detector Modem |
5
|
Each
|
500
|
N/A
|
2,500
|
Miscellaneous |
1
|
Each
|
5,000
|
N/A
|
5,000
|
Total Equipment Costs |
$108,503
|
Initial Cost Estimates for WB IH-20 VSL Site, Ranger Hill, Eastland County.
Equipment |
Quantity
|
Payment Unit
|
Unit Cost ($)
|
Monthly Cost ($)
|
Total Cost($)
|
---|---|---|---|---|---|
Reduced Speed Ahead PCMS |
1
|
Monthly
|
2,708
|
2,708
|
10,832
|
VSL PCMS—Base |
4
|
Monthly
|
2,708
|
10,832
|
43,328
|
VSL PCMS—Modifications |
4
|
Monthly
|
519
|
2,076
|
8,304
|
Vehicle Detector |
4
|
Each
|
5,500
|
N/A
|
22,000
|
Roadway Visibility Sensor |
1
|
Each
|
5,224
|
N/A
|
–
|
Roadway Condition Sensor |
1
|
Each
|
11,315
|
N/A
|
–
|
Vehicle Detector Modem |
5
|
Each
|
500
|
N/A
|
2,000
|
Miscellaneous |
1
|
Each
|
5,000
|
N/A
|
5,000
|
Total Equipment Costs |
$91,464
|
Evaluation of TxDOT Variable Speed Limit Pilot Projects: Final Report
Four VSL System configurations: $180,487; $116,187; $108,503; and $91,464.