The Interrelationships between Speed Limits, Geometry, and Driver Behavior Final Report

The relationship between speed and safety continues to be a high-priority research topic as numerous states consider speed limit increases. This study leveraged data from the Second Strategic Highway Research Program (SHRP2) Naturalistic Driving Study (NDS) to examine various aspects of driver behavior, including speed limit selection and engagement with in-vehicle distractions, as well as the impacts of these behaviors on crash risk while controlling for the effects of traffic, geometric, and environmental conditions. High-resolution time-series data were analyzed to examine how drivers adapt their speed on roadways with different posted limits, in speed limit transition areas where increases or decreases occur, as well as along horizontal curves, both with and without posted advisory speeds.  This report is available from the Center for Transportation Research and Education at Iowa State University web site: https://intrans.iastate.edu/app/uploads/2018/12/speed_limits_geometry_driver_behavior_interrelationships_w_cvr.pdf