Travel Time Evaluation of a U-Turn Facility and Its Comparison with a Conventional Signalized Intersection

Abstract

Signalized intersections on high-volume arterials are often congested during peak hours, causing a decrease in through movement efficiency on the arterial. Much of the vehicle delay incurred at conventional intersections is caused by high left-turn demand. Unconventional intersection designs attempt to reduce intersection delay and travel time by rerouting left-turns away from the main intersection and replacing it with “right-turn followed by U-turn”. The proposed new type of U-turn intersection is geometrically designed with a raised island which provides a protected U-turn movement. In this study several scenarios based on different distances between U-turn facility and present intersection, traffic volume on major/minor approaches and percentage of left-turn volumes were simulated using AIMSUN; a microscopic traffic simulation software. Subsequently some models are proposed in order to predict travel time of each movement at the intersection. Eventually by correlating these models to some in-field collected data of some real-life implemented U-turn facilities, the reliability of the proposed models is approved. With these models it would be possible to calculate travel time of each movement under any kind of geometric features and traffic conditions. By comparing travel time of a conventional signalized intersection with U-turn facility, it is possible to decide on converting signalized intersections into this new kind of U-turn facility or not. In this paper only travel time of this U-turn facility will be modeled. According to some before and after study about the traffic performance of some selected U-turn facilities, it is found that commonly, this new type of U-turn facility produces lower travel time. Thus, evaluation of using this type of unconventional intersection should be seriously considered.