Flow feasibility condition analysis and design optimization of contraflow left-turn lanes at signalized intersections based on kinematic wave theory

Dynamic left turning using lanes exiting an intersection in the opposite direction is a new type of left-turn traffic organization. When the left-turn traffic volume at an intersection is large, several exiting lanes adjacent to the original left-turn lanes can be converted into left-turn lanes during a certain period of free time under the control of a presignal. Based on kinematic wave theory, this paper analyzes the spatiotemporal process of the left-turn traffic flow. Three cases are analyzed, and the corresponding flow feasibility constraints are obtained in the form of requirements on the length of the contraflow left-turn lane and the coordination between the main signal and the presignal. Optimization of the lane length and signal coordination to maximize the number of vehicles entering the contraflow left-turn lane while guaranteeing traffic flow safety is discussed, and a practical example is analyzed.