Development of Guidelines for Implementation of Contraflow Left-Turn Lanes at Signalized Intersections

Recently, an innovative intersection design, contraflow left-turn lane (CLL) design has been increasingly implemented at the signalized intersections in China. It was designed for solving the problem that the capacity of the existing regular left-turn (LT) lanes is insufficient for the increasing left-turn demand at a signalized intersection. The basic idea of this design is to provide additional capacity to left-turning vehicles by making use of the opposing lanes dynamically. With the CLL design, more existing lanes (i.e. opposing through lanes) can be used for moving left-turn vehicles, thereby increasing the efficiency and capacity of the intersections and reducing the left-turn queue lengths at the intersections. In addition, this new design can be easily implemented without modifying the intersection in a way that requires major constructions. To introduce this cost-effective new design to the transportation practitioners in USA, the proposed study will systematically analyze the impacts of CLL on the intersection operational performance and will develop a model for estimating the length of the CLL that will maximize the operational benefits of this new design. In addition, traffic simulation based study will be conducted to valid the modeling results. After that, a step by step design procedure for converting an existing conventional LT intersection to a CLL will be developed. The outcome of the project will provide tools and design guidelines to the traffic engineers for appropriately implementing of this innovative intersection design in USA in the future.