The Interrelationships between Speed Limits, Geometry, and Driver Behavior

University Transportation Centers Program2018PDFTech ReportSavolainen, Peter T.Gates, Timothy J.Hamzeie, RahaKirsch, Trevor J.Cai, QiuqiIowa State University. Center for Transportation Research and EducationMidwest Transportation CenterMichigan Department of TransportationUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramUnited States. Department of Transportation. Office of the Assistant Secretary for Research and TechnologyIowa State University. Center for Transportation Research and EducationUnited StatesBehaviorCrash risk forecastingDecelerationDistractionDriversGeometric designHighway curvesReaction timeSpeed limitsDTRT13-G-UTC37Final reportThe 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. The research also involved an investigation of the circumstances under which driver distraction is most prevalent. The factors associated with crash and near-crash events were compared with similar data from normal, baseline driving events across various scenarios to improve understanding of the nature of the precipitating events. Driver responses, including reaction times and deceleration rates, were examined during the course of crash and near-crash events to determine how driver response varied across various scenarios. Ultimately, this research provided important insights as to how drivers adapt their behavior and how these behaviors, in turn, influence the likelihood of being crash involved.143