Safety Evaluation of Right Turns Followed by U-Turns at Signalized Intersections (6 or More lanes) as an Alternative to Direct Left Turns - Conflict Analysis

This report is one of two reports of the project that evaluated the safety and operational impact of a right turn followed by a U-turn (RTUT) at a signalized intersection as an alternative to a direct left turn (DLT) from driveways and side streets. This report evaluated the safety of both alternatives by comparison of traffic conflicts. Nine types of conflicts were selected for this study. Five of the conflicts were related to RTUT movements, while the rest of them were related to DLT movements. Data were collected with the help of video recording equipment at a total of eight sites for over 300 hours. Descriptive analysis and conflict rate analysis were conducted. Two types of conflict rates, conflicts per hour and conflicts per thousand involved vehicles, were used for safety comparison of the two left turning alternatives. DLT movements generated on average 6.7 conflicts per hour, while RTUT movements generated 2.4 conflicts per hour. On the other hand, the average number of conflicts per thousand vehicles involved for DLT and RTUT movements were 40.6 and 26.2, respectively. Severity of conflicts was analyzed by Risk of Collision (ROC) score. In general, when both DLT and RTUT are compared, based on the results of this study, RTUT movements reduce the number of conflicts, and the overall severity of RTUT related conflicts are significantly lower than that of DLT related conflicts.