Field data collected over the last two decades show variable speed limit (VSL) systems can reduce crash potential by 8 to 30 percent.
A literature review of VSL systems in the United States and Europe
Made Public Date
12/07/2012

130

Orlando
Florida
United States

656

Covington
Virginia
United States

182

Northern Virginia
Virginia
United States

657

Utah
United States

658

Minnesota
United States

659

Munich
Germany

458

Netherlands

481

Autobahn
Germany

602

United Kingdom

6

Finland
Identifier
2012-00806
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Work Zone Variable Speed Limit Systems: Effectiveness and System Design Issues

Summary Information

In July 2008, a variable speed limit (VSL) system was implemented on a 7.5 mile section of I-495 (the Capital Beltway) in Virginia between the Springfield Interchange and the Woodrow Wilson Bridge. A study was conducted to examine performance and evaluate system impacts, and a literature search was performed to identify measures of effectiveness (MOEs) and gather information on VSL system and algorithm design.

FINDINGS

The data below excerpted from Table-1 of the source report highlights findings from the literature search.
 

Type of Test Location Major Findings
Field Germany, Autobahn 5 30% reduction in injury crashes [1]
United Kingdom, M25 10%-15% reduction in crashes [2]
The Netherlands 16% reduction in crashes and 3%-5% increase in system throughput [1]
Near Munich, Germany, Autobahn 9 Slow flow sustained during times of congestion; similar German VSL sections saw 20%-30% reduction in crash rates [2]; concept of speed-flow-density algorithm uncovered here [3]
Finland, Highway E18 Mean speed and speed variability decreased; projected crash rate decrease of 8%-25% [4]
Utah, I-80 work zone VSLs changed by time of day; some reduction in speed variance at entrance to activity area. [5]
Minnesota I-494 work zone Throughput increased 7% during 1 hour of day; no change in another hour; compliance with speed limits 20%-60%. [6]
Simulation Orlando, I-4 segment Best results involved 5 mi/hr increment change by decreasing upstream limits while increasing downstream limits or just simply increasing downstream limits [9]
I-64 in Covington, Virginia work zone evaluation The two logics concerned with reducing mean speeds produced safer conditions [10]
Northern Virginia VSLs alleviated dangerous drops in speed and reduced queue length but were less effective under heavy congestion [11]


[1] Mirshahi, M., et al. Active Traffic Management: The Next Step in Congestion Management, Report No. FHWA-PL-07-012, U.S. DOT FHWA. 2007.

[2] Robinson, M. "Examples of Variable Speed Limit Applications," Paper presented at the Speed Management Workshop, 79th Annual Meeting of the Transportation Research Board, Washington, DC. 9 January 2000.

[3] Bertini, R.L.; S. Boice; and K. Bogenberger. "Dynamics of a Variable Speed Limit System Surrounding a Bottleneck on a German Autobahn," Journal of the Transportation Research Board, TRR Report No.1978, Washington, DC, 2006, pp.149-159.

[4] Yrjo and Jukka. Southeastern Region, Finnish National Road Administration, December 1995. Research cited in the U.S. DOT ITS Knowledge Resources. (Benefit ID: 2007-00504).

[5] McMurtry, T., et al. "Variable Speed Limit Signs: Effects on Speed and Speed Variation in Work Zones," 88th Annual Meeting of the Transportation Research Board. Washington, DC. 2009.

[6] Kwon, E., et al. "Development and Field Evaluation of Variable Advisory Speed Limit System for Work Zones," Journal of the Transportation Research Board, TRR Report No. 2015, Washington, DC, 2007, pp.12-18.

[9] Abdel-Aty, M. and A Dhindsa. "Coordinated Use of Variable Speed Limits and Ramp Metering for Improving Safety on Congested Freeways," 86th Annual Meeting of the Transportation Research Board. Washington, DC. 2007.

[10] Park, B. and S. Yadlapati. Development and Testing of Variable Speed Limit Logics at Work Zones Using Simulation, University of Virginia. Charlottesville, VA. 2002.

[11] Mazzenga, N.J. ,and M.J. Demetsky. Investigation of Solutions to Recurring Congestion on Freeways, Report No. VTRC 09-R10, Virginia Transportation Research Council. Charlottesville, VA. 2009.

Work Zone Variable Speed Limit Systems: Effectiveness and System Design Issues

Work Zone Variable Speed Limit Systems: Effectiveness and System Design Issues
Publication Sort Date
03/01/2010
Author
Fudala, Nicholas J. and Michael D. Fontaine
Publisher
Virginia DOT

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