Benefit

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


03/01/2010
Autobahn,Germany; United Kingdom; Netherlands; Munich,Germany; Finland; Utah,United States; Minnesota,United States; Orlando,Florida,United States; Covington,Virginia,United States; Northern Virginia,Virginia,United States


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 TestLocationMajor Findings
FieldGermany, Autobahn 530% reduction in injury crashes [1]
United Kingdom, M2510%-15% reduction in crashes [2]
The Netherlands16% reduction in crashes and 3%-5% increase in system throughput [1]
Near Munich, Germany, Autobahn 9Slow 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 E18Mean speed and speed variability decreased; projected crash rate decrease of 8%-25% [4]
Utah, I-80 work zoneVSLs changed by time of day; some reduction in speed variance at entrance to activity area. [5]
Minnesota I-494 work zoneThroughput increased 7% during 1 hour of day; no change in another hour; compliance with speed limits 20%-60%. [6]
SimulationOrlando, I-4 segmentBest 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 evaluationThe two logics concerned with reducing mean speeds produced safer conditions [10]
Northern VirginiaVSLs 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.

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Source

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

Author: Fudala, Nicholas J. and Michael D. Fontaine

Published By: Virginia DOT

Source Date: 03/01/2010

Other Reference Number: Report No. FHWA/VTRC 10-R20

URL: http://www.virginiadot.org/vtrc/main/online_reports/pdf/10-r20.pdf

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Goal Areas

Safety
Efficiency

Typical Deployment Locations

Metropolitan Areas, Rural Areas, Statewide

Keywords

smart work zone systems, VSL, smart work zone, smart work zones, Smart work zones, workzone, WZ

Benefit ID: 2012-00806