Project Summary
Speed limits reflect a trade-off between highway safety and mobility. There are two schools of thought for setting speed limits: uniform speed limit (USL) and differential speed limit (DSL). Previous literature shows contrasting evidence on the crash frequency and severity for both scenarios. The research team’s previous work has shown that increasing speed limits (either USL or DSL) from current 55/65mph to different levels would increase speed related crashes and fatalities, more so in urban areas than in rural areas. But the data limitation prevented the researchers from drawing a conclusion on the relative merits of USL vs DSL. It also prevented an assessment of its impact on traffic operations.
This project will use roadway, traffic, and crash datasets for sampled freeway segments, coupled with microscopic traffic simulation, to evaluate the full impact of various speed limit options from both safety and operational perspectives. The work will measure the impacts in monetary terms. Total travel times/distances and total number of crashes will be used to estimate the cost components. Through this combined data driven and simulation approach, the team attempts to provide a conclusive assessment of speed limit policies that has eluded researchers.
