CORSIM-Based Simulation Approach to Evaluation of Direct Left Turn versus Right Turn Plus U-Turn from Driveways

Right turn plus U-turn at median openings as an alternative to direct left turn has been considered important issue in access management. The motivation behind using this strategy comes from the consideration of safety as well as from traffic operational performance. The objective of this study was to evaluate the operational performances of direct left turn and right turn plus U-turn through simulation. This study attempted to figure out under what traffic conditions replacing a direct left turn with a right turn plus U-turn would be beneficial from an operational point of view. CORSIM, a combination of FRESIM and NETSIM, was selected as the analytical tool in the study due to its strong capability in road network evaluation and its animation display function. A total of six sites were selected to do the field data collection. The delay and travel time were used as the measures of effectiveness (MOE) in evaluating the operational performance of direct left turn (DLT) and right turn plus U-turn (RT+UT). The site-specific simulation models for the six sites were developed using CORSIM. Each model was calibrated based on the field data. The comparisons between DLT and RT+UT in terms of the delay and travel time have been conducted under different levels of traffic volume. The simulation results showed that, with an increase in the through-traffic volume on the major road, the delay as well as the travel time of DLT were higher than those of RT+UT. This information is very useful for decision makers in determining what kind of median opening will be applicable under the given traffic conditions.