Rural variable speed limit system for southeast wyoming

Variable speed limit (VSL) is a type of intelligent transportation system that has shown promise for improving safety on roadways that are subject to adverse weather conditions. A new rural VSL system was installed by the Wyoming Department of Transportation along I-80 in the southeastern part of the state. Statistics on the use of the system during its initial months of implementation are presented along with analyses of the impact on observed speeds of measured weather variables and speed limits on the VSL system. Preliminary results indicate that drivers reduce their speeds by 0.47 to 0.75 mph for every mile per hour in posted speed reduction. The research lays the foundation for a decision support system that will be used in future operations of the VSL system.