Travel Time Evaluation of a U-Turn Facility

Abstract

Drivers on high-volume arterials with signalized intersections often face congestion during peak hours. This congestion, primarily through movement, decreases the traffic performance of the intersection. The primary delay at conventional intersections is caused by interactions between high left-turn movements and the opposing through maneuvers. Unconventional intersection designs have been proposed to decrease intersection delay and travel time, for example, by redirecting left turns from the minor approach away from the main intersection and replacing them with a right turn followed by U-turn. The U-turn intersection investigated in this study is geometrically designed with a raised island, which provides a protected U-turn movement. Several scenarios with different distances between the U-turn facility and the intersection, traffic volume on major and minor approaches, and percentage of left-turn volumes were simulated by using AIMSUN (Advanced Interactive Microscopic Simulator for Urban and Non-Urban Networks) software. Models were created to predict travel time for each movement at the intersection and were validated against data collected from a number of U-turn facilities. With these models, it was possible to calculate travel time of each movement within boundaries of geometric features and traffic conditions indicated in this study. Finally, by comparison of the travel time of a conventional signalized intersection with that of a U-turn facility, an objective criterion was obtained for use in deciding on the possible conversion of a signalized intersection into this new kind of U-turn facility. According to the results of this comparison, this type of U-turn facility generally produces lower travel time. Thus, evaluation of using this type of unconventional intersection should be seriously considered.