Simulation Analysis Of Left-Turn Traffic Organization Method At Urban Road Intersection

Urban road intersection is the key node in the whole urban traffic network.It is the main research direction of relevant scholars and staff to solve the problem of traffic congestion at the intersection and to improve the capacity of the intersection.Compared with direct traffic flow and right-turn traffic flow,left-turn traffic flow requires longer driving distance and time,and it is more likely to cause traffic conflict with other phase traffic flow and pedestrian flow.The traffic condition of left-turn directly affects the traffic flow of other phases and the traffic capacity of intersection.Therefore,there are great significance of researching left-turn traffic,to solve urban road traffic congestion.About left-turn Traffic at Urban Road intersection,there are many weaving methods.Compared with other left-turn traffic modes,reverse variable-lane,short-lane and variable-lane are applied later,many details are not perfect,and there is also space to improve the traffic capacity of intersection.Therefore,this paper takes reverse variable-lane,short-lane and variable-lane,as the research object,and chooses the cellular automaton model which is commonly used in the traffic flow research field as the research method.In this paper,this three methods of left-turn flow organization are simulated and studied.The main work of this paper is as follows:(1)The left-turn traffic organization method and traffic flow theory at home and abroad are studied in an all-round and profound way.The implementation process of three left-turn traffic organization methods,the NS rules,lane-changing rules and boundary conditions used in the cellular automaton model in this paper are described in detail.(2)The influence factors of traffic capacity of reverse variable-lane intersection are analyzed,and the cellular automaton model of reverse variable-lane intersection is established according to the usage rules of reverse variable-lane intersection.The traffic flow condition for setting reverse variable-lane,and the influence that the length of reverse variable-lane,green light duration and exit traffic flow have,on the traffic capacity of intersection,are simulated.The simulation results show that there is a critical value of the flow rate of the left-turn vehicle.When the arrival rate of the left-turn traffic reaches this critical value,the traffic capacity of the intersection can be improved by setting the reverse variable-lane.Otherwise,there is no need to set the reverse variable-lane.When the signal period and arrival rate are fixed,there is an optimal length of reverse variable-lane to maximize the traffic capacity of the intersection.And when the arrival rate of the exit traffic flow is small,the reverse variable-lane can be set to play a useful role.(3)The influence factors of traffic capacity of short-lane intersection are analyzed,and the cellular automaton model of short-lane intersection is established according to the usage rules of short-lane intersection.The traffic flow condition of setting short-lane and theinfluence that the length of the short-lane,the release mode of direct traffic flow and left-turn traffic flow,and signal cycle have,on the traffic capacity of intersection,also the effect of short-lane on the evacuation efficiency of reverse traffic flow,are simulated.The simulation results show that there is a critical value of the left-turn flow rate,when the arrival rate of the left-turn traffic reaches this critical value,the traffic capacity of the intersection can be improved by setting a short-lane.Otherwise,there is no need to set the short-lane.There is a lower probability of clogging and greater traffic capacity than other two release way for one-port release way,in the short-lane intersection.When the arrival rate and the signal period are certain,there is a best short-lane length to maximize the capacity.When the short-lane length is lower than this optimal length,the traffic capacity of intersection can be improved by increasing the length of short-lane.The evacuation efficiency is significantly affected by the length of short-lane when the arrival rate of reverse direct traffic flow is large,and the greater the length of short-lane is,the greater the degree of evacuation efficiency is affected.And there is an optimal signal cycle time to maximize the capacity of the short-lane intersection.(4)The influence factors of traffic capacity of variable-lane intersection are analyzed,and the cellular automaton model of variable-lane intersection is established according to the usage rules of variable-lane intersection.This model mainly simulates whether setting variable-lane can improve the traffic capacity of intersection when the arrival rate of left-turn traffic flow and direct traffic flow are not balanced.The influence that the green signal ratio and the direct green signal ratio have on the traffic capacity of the intersection are simulated.The simulation results show that when heavy traffic flow occurs in one direction of left turn and straight line,the traffic capacity can be improved by setting a variable-lane.And even if the arrival rates of traffic flow in both directions are high,the traffic capacity of intersection can by improved as much as possible by changing the attribute of variable-lane.The direct phase and the left-turn phase green signal ratio have significant influence on the traffic capacity of the variable-lane intersection.And increasing the green signal ratio of heavy traffic flow direction can improve the traffic capacity of the intersection to a certain extent.