The Influence of Driver Sight Distance on Crash rates and Driver Speed at Modern roundabouts in the united States

Michael angelasTro, p.e., pToe inTroducTion The objective of this paper is to establish that vehicle speeds and crash rates at modern roundabouts in the United States are related to driver sight distance. This paper investigated the relationship between driver sight distance and passenger vehicle speeds and vehicle crash rates at roundabouts in the United States based on data collected at 26 single-lane roundabouts. The 85th percentile speed parameter was selected as an analysis technique because the current operating speed models for other roadway elements evaluate design consistency using this parameter. Models were developed that predict the 85th percentile approach speed, 85th percentile entrance speed, and the difference between the 85th percentile approach and 85th percentile entrance speeds. Models were developed to predict vehicle crash rates at roundabouts considering driver sight distance. The models presented in this paper can be used to estimate the speeds at the approach and entrance to a roundabout and crash rates at modern roundabouts in the United States.