Location of U-Turn Openings at Signalized Intersections Based on Optimal Traffic Capacity

In order to solve the unreasonable deployment of U-turn openings at signalized intersections, a method is proposed to calculate locations of optimal U-turn openings based on the optimal traffic capacity by taking the traditional four-phase control intersection as an object. Firstly, a loss time model of lanes shared by left-turn and U-turn vehicles is built to reveal the interaction mechanism between left-turn and U-turn traffic flows in different traffic conditions. Then, a capacity calculation model of lanes shared by left-turn and U-turn vehicles is established using the probability distribution function of vehicles in different flow directions. The capacity-location (C-L) curve drawn by the model can fully reveal the capacity characteristics of the shared lanes under influence of the U-turn openings. Based on the maximum capacity, the optimal location of U-turn openings is finally determined. In addition, the validity of the method was verified through a case study in the central area of Zibo City. The result shows that the proposed method can improve the traffic capacity of the shared lane of left-turn and U-turn vehicles from 432 to 509 pcu/h by 17.82%.