Procedure for Evaluating the Impacts of Indirect Driveway Left-Turn Treatments on Traffic Operations at Signalized Intersections

Abstract

The use of nontraversable median cross sections and directional median openings has generated increased numbers of U-turning vehicles at signalized intersections. A procedure is needed to help transportation professionals determine the impacts of proposed median-modification projects on traffic operations at downstream signalized intersections. This study is a continuous effort following previous studies to evaluate the impacts of indirect driveway left-turn treatments on traffic operations at signalized intersections. In the present study, a total of 80 h of traffic data were collected at 66 roadway segments in the Tampa Bay area of Florida. On the basis of the data collected in the field, the research team developed a negative-binomial model to estimate the expected number of U-turning vehicles on a left-turn approach at a signalized intersection during weekday peak periods. The model has only five independent variables, and all of these variables can be easily measured in the field. By combining the research results of this study and previous studies, a procedure is provided to help transportation professionals evaluate the impacts of proposed indirect driveway left-turn treatments on traffic operations at downstream signalized intersections.