variable speed limits - texas a&m university · 2017. 1. 4. · findings of vsl pilot study l...

Texas Pilot Project

October 13, 2015

VARIABLE SPEED LIMITS

Table of Contents

2

3-4Variable Speed Limits (VSL) - Introduction

VSL - Operation

HB 2204 Pilot Study – Methodology

1

3

4

17-18

19-26

Lessons Learned & Closing Remarks6 34-42

VSL - Defined2 5-16

HB 2204 Pilot Study – Findings5 27-33

Questions7

Variable Speed Limit (VSL) l What is it?

3

Simply put, it’s a speed limit that changes

when activated based on the conditions of

the road including construction, congestion,

and weather.

What is a Variable Speed Limit?

VSL l History

4

Michigan (1960) – First VSL

Netherlands

Germany

Finland

England

Europe

Washington

Michigan

New Jersey

Tennessee

New Mexico

Flag Images: http://www.flags.net/

United States

5

VSL l Defined

What Activates a VSL?

• Lane Closures

Construction

• Volume

• Speed

• Occupancy

Congestion

• Surface Friction

• Visibility

Weather

6

VSL l Defined

Example for illustrative purposes.

Not to scale & missing required signage.

Congestion

• Increased Volume/Occupancy

• Reduced Speeds

VSL

Measured

Speed76 74 72 68 77 75 74 72 65 68

7

VSL l Defined




• Reduced Speeds

VSL

Measured

Speed69 71 75 76 74 69 70 73 68 52

Congestion

8

VSL l Defined




• Reduced Speeds

VSL

Measured

Speed73 76 75 72 77 73 57 37 40 32

Congestion

9

VSL l Defined



VSL

Measured

Speed71 75 77 42 37 32 35 20 31 28

Congestion


• Reduced Speeds

10

VSL l Defined




• Reduced Speeds

VSL

Measured

Speed73 76 75 73 68 71 69 50 34 28

Congestion

11

VSL l Defined




• Reduced Speeds

VSL

Measured

Speed73 76 75 73 76 77 69 71 73 68

Congestion

12

Construction

Status: No Work Present

VSL l Defined



• Lane closure

• Other congestion event

13



VSL l Defined

Status: Lane Closure

• Lane closure

• Other congestion event

Construction

14

Status: All Clear

Weather

VSL l Defined

Example for illustrative purposes. Not to scale.

• Reduced Visibility

• Reduced Surface Friction

15

Status: Weather Event

VSL l Defined

Example for illustrative purposes. Not to scale.

Weather



Visibility

Surface Friction

16

VSL l Defined

Dry Wet Ice/Snow

Good 65 45 30

Poor 50 40 30

Example from Pilot Study

Weather



17

½ mi to 1 mi

VSL l Operation

►Signs spaced ½ mi to 1 mi

►Transitions of 5, 10, 15 mph – except downstream

►Speed harmonization via Troupes

7055

45 40 35

70

18

VSL l Operation

• VSL system pings the traffic

management center if it detects

need for VSL

• An operator has the ability to

accept/deny the implementation of

VSL

• System will notify operator when

conditions have returned to normal

• Operator “acknowledges”

deactivation. Important information

is logged in the system, such as

date, time, speeds that were set

during VSL, etc.

Activation

De-activation

19

83rd Session

2013HB 2204

20

HB 2204 Pilot Study

Selected 3 pilot locations w/ Construction, Congestion, & Weather pilot studies

Bill expired February 2015

Worked with TTI &Southwest Research Institute

HB 2204 Pilot Study

21

Construction

Temple – Belton

I-35

Congestion

San Antonio

SL 1604

Weather

Ranger

I-20

22

Google.com/maps

Temple - BeltonI-35 (NB)

HB 2204 Pilot Study l Construction VSL

X Visibility

23

Activation Initial Observations

► 2014: June 23 – Nov. 30

► Thunderstorm when first activated

► Included Pavement Sensors

► Weather detection devices needed calibration

► Complaints on visibility / location of signs

► July 3 – Thunderstorm destroyed two signs

HB 2204 Pilot Study l Construction VSL

Temple-BeltonI-35 NB

24

Google.com/maps

HB 2204 Pilot Study l Congestion VSL

San AntonioLoop 1604 (WB)

Google.com/mapsGoogle.com/maps

X Visibility

Activation

► 2014: June 30 – Dec. 31

► Included Pavement Sensors

► Congestion related activation occurred on a daily basis

25

I-20

Ranger Hill

Google.com/maps

HB 2204 Pilot Study l Weather VSL

Google.com/maps

Google.com/maps

26

Activation

I-20

Ranger Hill

?► July 21, 2014 – Jan. 30, 2015

► Included Pavement Sensor & Visibility Sensor

HB 2204 Pilot Study l Weather VSL

27

0

100

200

300

400

500

600

700

800

San Antonio Temple Ranger Hill

745

220

112

Total Activations

Findings of VSL Pilot Study l Overall

San AntonioLoop 1604 (WB)

28

Findings of VSL Pilot Study l Congestion

June Sept. Oct. Nov. Dec.

At each VSL Location► Before Pilot Study: Average speeds were recorded in June during the evening peak period

► During: Average speeds were recorded a few days each month during evening peak period

Before During

Comparison

of Average

Speeds

(Next Slide)

18th

25th

July

17th

24th2nd

9th

23rd

19th 13th 11th

18th

29

Findings of VSL Pilot Study l Congestion

Google.com/maps

N

70

60

50

40

30

20

VSL Locations

December

November

September

October 2 & 9

June

July

October 23

No VSL

Comparison of Average Speeds - Peak Period

60

50

40

30

20

31

Crashes by Severity

Findings of VSL Pilot Study l Safety

32

Crashes by Adverse Surface Conditions

Findings of VSL Pilot Study l Safety

33

User Perception of VSL Message

Question: “What do you think the signs were telling you?”

Findings of VSL Pilot Study l Perception

34

Average Speeds, With & Without Enforcement

Findings of VSL Pilot Study l Enforcement

10096

60

9

0

65

9

0 0 00

20

40

60

80

100

120

> 55 > 60 > 65 > 70 > 75

Speed Threshold (MPH)

% of Avg.

Speeds

Exceed that

Threshold

Posted Speed

w/ Active VSL

No Enforcement

Enforcement Present

35

Findings of VSL Pilot Study l Lessons Learned

1. Use permanent equipment preferably mounted over the

travel lanes. Temporary equipment was not suitable for long-

term operations.

36


2. A wider separation of the sensors and signs would be

necessary for permanent installations.

37


3. Site selection process – more

rigorous & comprehensive

– Longitudinal and horizontal

spacing considerations

– Traffic operations with

respect to ingress/egress

locations

– Understanding the existing

speed profile on any

proposed corridors

– Significant data collection

before implementation

38


4. Enhance operations to account for more failure conditions

in both equipment and communications. The algorithm can

be enhanced to address issues and increase public

confidence in messages posted by ensuring that they are

correct and consistent.

39


5. Additional efforts to improve the overall algorithm are

warranted, with multiple avenues being identified to enhance

future operations, such as adjustments to sensor inputs,

analysis, and spacing.

40


6. Consideration needs to be given to real-time data

exchange to other agencies, such as the Department of

Public Safety.

?

? ?

41


7. Significant and on-going public outreach is necessary to

assist drivers in both understanding and complying with

variable speed limits.

42

0

2

4

6

8

0 10 20-10-20Deviation from Mean Speed (mph)

OVERTAKINGS

ACCIDENT

INVOLVEMENT

►Greater Safety

►Efficient Use of Highway Facilities

►Increased Compliance

►Congestion Relief

More Speed Deviations = More RiskRisk

Findings of VSL Pilot Study l In Closing

VSL - The Potential Benefits

43

Findings of VSL Pilot Study l In Closing

►Federal Highway Administration (FHWA) tool used for B/C analysis

►Full permanent installation assumed

►Benefit predictions based on 7% crash reduction

Deployment

Site

Annual

Benefits

Annual Cost Net Benefit B/C Ratio

San Antonio $2,112,983 $300,370 $1,812,613 7.03

Temple $2,358,976 $238,075 $2,120,901 9.91

Ranger Hill $4,216,950 $300,370 $3,916,580 14.04

Benefit Cost Analysis

Texas Pilot Project

VARIABLE SPEED LIMITS

Darren McDaniel, PE

Texas Department of Transportation

Beverly Kuhn, PE

Texas Transportation Institute

variable speed limits - texas a&m university · 2017. 1. 4. · findings of vsl pilot study l...

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