Design And Optimization Methods Of Left-turn Traffic Organization At Signalized Intersections

ABSTRACT:Left-turn traffic is the critical cause of the conflicts, delays and reduction of capacity at signalized intersections. In order to improve the efficiency and reduce the accident rate of the intersections, it's important to organize the left-turn traffic flows effectively. Currently, most left-turn traffic organization methods are used according to the practical experiences, as the research on the relevant theories is limited. Therefore, an intensive study on the characteristics of the traffic flows based on the relevant research achievements is carried out. From the points of time, space and policy management, the thesis discusses the use and optimization design of three kinds of left-turn traffic organization methods, which are set up of exclusive left-turn signal phase, set up of left-turn waiting areas and U-turn traffic organization. The main work completed is included below:1. Establishing a model for the calculation of passing numbers of the left-turn vehicles based on the traffic wave theory, which is used for the left-turn lanes without exclusive signal phase and takes the factors of the ratio of bus, saturation of traffic flow and length of signal cycle into account.2. Studying on the relationships between the effects of the exclusive left-turn signal phase and the volume of the left-turn and through traffic flows, based on the analysis of the conflicts and evaluations of delays.3. Studying on the relationships between the effects of the left-turn waiting areas and the arrival rates of the lanes, based on the queue analysis at different signal phases. What's more, the thesis proposes a method to determine the minimum green time and a model to revise the index of stop rate for the lanes with left-turn waiting areas.4. Putting forward a method to determine the u-turn location, which is consist of three conditions based on the idea of "green wave" and time-space diagram, queue analysis, as well as calculation of length of weaving area.5. Comparing the organization effects of the direct left-turn and U-turn based on the delay analysis of different operation phases, which provides evaluation ideas for the implementation of the "No Left" policy.In addition, the thesis validates the relevant theory and proposes optimization schemes of the left-turn traffic organization at the signalized intersections through practical examples.