Impact of Variable Speed-Limit System on Driver Speeds during Low-Visibility Conditions
Publication: Journal of Transportation Engineering, Part A: Systems
Volume 145, Issue 12
Abstract
Low-visibility conditions can inhibit a driver’s ability to perceive appropriate operating speeds, particularly during foggy conditions in which the characteristics of the fog can vary spatiotemporally. Numerous agencies have installed countermeasures such as weather advisory systems and variable speed limits (VSLs), but the results have not been analyzed quantitatively. This paper assesses how the I-77 fog VSL system in Fancy Gap, Virginia, affected driver speeds since its activation in October 2016. Prior to implementing the VSL, mean speeds were twice the safe speed based on stopping site distance (SSD) during fog. The VSL system sought to encourage drivers to travel closer to the SSD-based safe speed by posting appropriate reduced speed limits. The results indicated statistically significant reductions in mean speeds after the VSL was activated, and drivers drove closer to the safe speed based on available visibility. Compliance with the posted variable speed limit generally improved once drivers encountered reduced visibilities. Given the short period since activation, insufficient crash data existed to perform a complete safety analysis. However, the preliminary results indicated very promising safety trends for fog-related crashes. The results of this VSL implementation may serve as a reference for other agencies contemplating alternatives to improve safety in fog-prone areas and indicate that the countermeasure had a positive effect.
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Acknowledgments
The authors would like to thank Katie McCann, Mike McPherson, and Tim Martin from the Virginia Department of Transportation for their assistance, support, and insights into the process of this research.
References
AASHTO. 2011. A policy on geometric design of highways and streets. 6th ed. Washington, DC: AASHTO.
Abdel-Aty, M., M. M. Ahmed, J. Lee, Q. Shi, and M. Abuzwidah. 2012. Synthesis of visibility detection systems. Orlando, FL: Florida Dept. of Transportation.
Abdel-Aty, M., A. Ekram, H. Huang, and K. Choi. 2011. “A study on visibility obstruction related crashes due to fog and smoke.” Accid. Anal. Prev. 43 (5): 1730–1737. https://doi.org/10.1016/j.aap.2011.04.003.
Brooks, J. O., M. C. Crisler, N. Klein, R. Goodenough, R. W. Beeco, C. Guirl, and C. Beck. 2011. “Speed choice and driving performance in simulated foggy conditions.” Accid. Anal. Prev. 43 (3): 698–705. https://doi.org/10.1016/j.aap.2010.10.014.
Das, S., B. K. Brimley, T. Lindheimer, and A. Pant. 2017. Safety impacts of reduced visibility in inclement weather. College Station, TX: Center for Advancing Transportation Leadership and Safety, Univ. of Transportation Centers Program.
Goodwin, L. 2003. Best practices for road weather management, version 2.0. Washington, DC: US Dept. of Transportation.
ITS Decision, California DOT. 2017. “Traffic control in adverse weather.” Accessed July 1, 2017. http://fresno.ts.odu.edu/newitsd/ITS_Serv_Tech/weather_app/weather_applications_weather_traffic_control_report.html.
Kimley-Horn and Associates. 2014. Synthesis of practice for weather-related variable speed limit systems in the United States. Virginia Beach, VA: Kimley-Horn and Associates.
Kimley-Horn and Associates. 2015. I-77 Variable speed limit: Methodology for establishing variable speed limits. Virginia Beach, VA: Kimley-Horn and Associates.
Kyte, M., P. Shannon, and F. Kitchener. 2000. Idaho storm warning system operational test. Boise, Idaho: Univ. of Idaho.
Liu, J. 2003. “Fog detection and warning system.” Accessed July 24, 2017. https://www.pcb.its.dot.gov/t3/s130130/s130130_caltrans.pdf.
MacCarley, C. A., C. Ackles, and T. Watts. 2006. “Highway traffic response to dynamic fog warning and speed advisory messages.” Transp. Res. Rec. 1980 (1): 95–104. https://doi.org/10.1177/0361198106198000114.
McCann, K., and M. D. Fontaine. 2016. Investigation of driver speed choice and crash characteristics during low visibility events. Charlottesville, VA: Virginia Dept. of Transportation.
Murphy, R., R. Swick, and G. Guevara. 2012. Best practices for road weather management, version 3.0. Washington, DC: USDOT.
Naval Meteorology and Oceanography Command, US Naval Observatory. 2016. “Sun or moon rise/set table for one year.” Accessed June 5, 2017. http://aa.usno.navy.mil/data/docs/RS_OneYear.php.
Snowden, R. J., N. Stimpson, and R. A. Ruddle. 1998. “Speed perception fogs up as visibility drops.” Nature 392 (6675): 450. https://doi.org/10.1038/33049.
WXII 12 News. 2013. “Three dead, twenty-five injured in massive pileup on I-77 in Carroll County.” Accessed July 6, 2017. http://www.wxii12.com/article/3-dead-25-injured-in-massive-pileup-on-i-77-in-carroll-county/2049746.
Information & Authors
Information
Published In
Journal of Transportation Engineering, Part A: Systems
Volume 145 • Issue 12 • December 2019
Copyright
©2019 American Society of Civil Engineers.
History
Received: Oct 24, 2018
Accepted: Apr 24, 2019
Published online: Sep 25, 2019
Published in print: Dec 1, 2019
Discussion open until: Feb 25, 2020
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