Impacts of Separation Distances Between Driveway Exits and Downstream U-turn Locations on Safety Performance of Right Turns Followed by U-turns.

The primary objective of this study is to evaluate how the separation distances between driveway exits and downstream U-turn locations affect the safety performance of right-turns followed by U-turns. To achieve the research objective, crash data were collected at 140 street segments in the state of Florida. The selected sites were divided into three groups based on the separation distances measured in the field. T-tests and proportionality tests were performed for comparing crash frequency, crash type, and crash severity between different separation distance groups. Negative-Binomialmodels were developed for examining the factors that contribute to the crashes at selected street segments. The data analysis results show that theseparation distances significantly impact the safety of the street segments between driveways and downstream U-turn locations. A 10% increase in separation distance will result in a 3.3% decrease in total crashes and a 4.5% decrease in target crashes. The models also show that providing U-turnsat a signalized intersection will result in more crashes at weaving sections. Thus, if U-turns are to be provided at a signalized intersection, a longer separation distance shall be provided. The results of the study provide transportation decision makers with quantified results about the safety effects of the separation distances between driveways and U-turn locations and are particular helpful in selecting the optimal location of a U-turn bay to facilitate drivers make right-turns followed by U-turns.