Research On The Setting And Signal Control Method Of Left-turn Waiting Area In The Permitted Phase

With the increase of car ownership in China,intersection congestion is no longer a unique problem in first-tier cities,and the traffic congestion in fourth tier cities is becoming more and more serious.The root cause of traffic congestion is the existence of traffic conflicts,while the conflict between the through vehicles and left-turn vehicles results in most of the delay of the intersection.How to effectively alleviate or even eliminate the traffic conflicts is the fundamental measure to reduce the delay of the intersection.In this paper,the problem of serious traffic conflicts and low traffic efficiency between through vehicles and left-turn vehicles is studied.First of all,two typical permitted intersections are selected,which all have three phases.The investigation is carried out from the channelization design,signal scheme,traffic flow and traffic conflicts.The data of headway,traffic conflicts and saturation flow rate are statistically analyzed,and the existing problems of traffic flow operation at permitted intersections are obtained.Secondly,the design method of the left-turn waiting area of the permitted intersection is proposed.Based on the design principle of the continuity and safety of the traffic flow,the design scheme and parameters of the left-turn waiting area under different conditions are given according to whether there is a central separation,including the geometric size,angle and number of lanes of the left-turn waiting area.The advantages and disadvantages of different release sequences are compared,and the phase sequence scheme and signal timing scheme are given,analyze the traffic conflicts of the intersection with the conventional waiting area and the intersections before and after the improvement,and verify the effectiveness of the design.Then,the optimized signal timing scheme is calculated quantitatively,and the average delay of vehicles model before and after the improvement is given by referring to Webster model.Taking the minimum average delay of vehicles at intersections as the optimization objective,the improved optimization model of signal control parameters at intersections is established and solved by exhaustive method.Using MATLAB software,this paper analyzes the influence of traffic volume,the proportion of left-turn vehicles and the capacity of left-turn waiting area on the delay of secondary road,in order to define the application scope of this design method.Finally,taking the intersection of Rongjiang road and Qunli Sixth Avenue in Harbin as an example,VISSIM simulation is carried out to compare and analyze the average delay and parking rate indexes of the intersection before and after the improvement,to verify the rationality and effectiveness of the design method in this paper.