Evaluation of the Operational and Safety Effects of a Variable Speed Limit System in Virginia

Variable speed limit (VSL) systems have been broadly deployed to address safety and mobility concerns both in the U.S. and internationally. In June 2022, the Virginia Department of Transportation activated a VSL system on I-95 northbound about halfway between Washington, D.C. and Richmond, Virginia. While many past VSL deployments have attempted to address urban congestion or mitigate safety issues arising from inclement weather, this deployment was intended to address traffic congestion created by through traffic during peak recreational periods by encouraging more uniform speed selection, dampening the effects of shockwaves, and providing advance warning of congestion. This paper discusses the characteristics of the deployed system, as well as its safety and operational effects, using approximately 1 year of post-deployment data. Results show that drivers did respond to the VSLs, and that mean speeds and speed distributions changed during transitional flow. Early safety results also showed reductions in crash severity, although this finding is based on limited data.