Safety Impacts and Other Implications of Raised Speed Limits on High-Speed Roads

This report describes the analyses performed and results obtained by a study of safety and other impacts of speed limit changes on high-speed roads. The information will be valuable for researchers studying the complex relationship between safety and vehicle speeds. The information also highlights limitations in the data needed to make sound regulatory decisions. The digest summarizes the results of NCHRP Project 17-23, which examined the effects of raised speed limits from 55 mph or greater on freeways and non-freeways, in both rural and urban settings. The effects considered included safety, operations, socioeconomics, and environmental.