Study On Modeling,Simulation And Optimization Of Left-turn Traffic Organization At Intersections

In recent years,the car ownership in China's big cities has increased greatly,and the traffic conflicts and contradictions are increasing,which causes traffic congestion,delay and traffic safety problems are becoming more and more serious.Intersections are important nodes of urban roads.The capacity of intersections determines the bearing capacity of urban roads.Because the intersection has to deal with the transformation of traffic flow in different directions in a limited space,its capacity is far lower than that of the section.The traffic flow diverges,combines and interweaves at the intersection,which aggravates the congestion at the intersection.Moreover,due to the continuous increase of urban traffic flow,the arrival rate of traffic flow at intersections is larger than the dissipation rate,which leads to vehicle queuing.If the queue length is larger than the maximum allowable length of the section and lane,the intersections will overflow,which causes great disturbance to the traffic efficiency of intersections.Therefore,this paper proposes a low-cost intersection improvement method,aiming to optimize left-turn traffic flow queuing and traffic signals,so as to improve the capacity and operation efficiency of the intersection.The research work of this paper mainly includes the following points:Firstly,field survey and data collection were carried out on typical intersections in chongqing,and the queue,parking number and delay of intersections were compared.On this basis,traffic flow characteristics are analyzed,including traffic flow operation characteristics,distribution characteristics and conflict characteristics.The problems existing in left-turn traffic flow at intersections are summarized and the evaluation parameters of intersections are proposed.Secondly,optimize the organization of left-turn traffic flow,and improve the setting of left-turn waiting area: determine the geometric conditions of the waiting area from three aspects: the distance between this left-turn traffic flow and the opposite direct traffic flow,the distance between this left-turn traffic flow and the opposite left-turn traffic flow,and the turning radius of the waiting area.The relationship between the queue length of left-turn vehicles and the lane is analyzed to determine the necessity of setting the waiting zone.The signal timing is determined by considering the relationship between left-turn phase and straight-line phase.On the basis of the above setting conditions,determine the setting range of the zone to be transferred.A parameter system was established to evaluate the circulation capacity,delay and queue length of left-turn traffic before and after setting up the waiting zone.Then,considering the applicability of left-turn waiting area,this paper also puts forward left-turn far-lead traffic organization optimization.The distance between the turning opening and the main intersection is determined from the parameters such as interleaving speed,design speed and the time of the straight traffic at the upstream and downstream signalized intersections.Determine the turning radius and channel width of the opening of the tele-guide,and calculate the setting range of the opening position of the tele-guide.Establish an evaluation parameter system for the implementation of left-turn remote citation at intersections,which is consistent with the selection of evaluation parameters in the waiting area.Finally,the selected intersections were investigated on the spot,and the actual traffic characteristic data of the intersections were collected.In combination with the channelization of the intersections and the current situation of signal timing,the VISSIM simulation platform was built,and the evaluation parameters established above were input into the simulation model.The traffic organization modes studied in this paper,such as the general waiting area,the improved waiting area,the left-turn far-lead,the left-turn far-lead and the special signal light,were simulated,and the feasibility and applicability of the optimization technology were verified by comparison and evaluation.