Research On Optimization Of Space And Time Resources For Variable Approach Lane At Urban Intersections

With the rapid development of China’s social economy,the urbanization process has entered a period of rapid development.The huge number of cars has brought great traffic pressure to urban roads.As a key node of the urban road network,intersections have become a prone place for traffic congestion.Improving the traffic efficiency of intersections is one of the keys to maintain the smooth flow of the urban road network.As a convenient and flexible space optimization method,the variable approach lane requires little traffic infrastructure and can change the lane attributes according to the actual traffic flow.At the same time,combined with signal optimization,the problem of drastic change in the turning flow of intersections can be alleviated,and the purpose of making full use of the space and time resources and improving the overall traffic efficiency at the intersection can be realized.On the basis of referring to the relevant literature,this paper summarizes the theoretical research on the optimization of intersections’ spatial and temporal resources.Based on the variable approach lane,a method to determine the setting threshold and an adaptive control system are proposed.Firstly,the distribution characteristics of turning traffic flow at intersections are studied.From the view of whether the traffic flow of each turn is saturated,the paper analyzes the operation and queuing characteristics of the traffic flow at the intersection entrance,and expounds the mismatching relationship between the traffic supply and demand.Furthermore,various influencing factors of the turning traffic distribution were analyzed,and the characteristics of the uneven distribution were summarized.In order to visually express the difference in the proportion of the turning flow in different time periods,the coefficient of the uneven distribution is put forward.Secondly,the threshold value and critical condition of setting variable approach lanes are studied.By investigating variable approach lanes in typical cities of China,the setting forms are divided into three categories,and the channelization conditions,traffic conditions and signal control conditions that need to be met in setting variable approach lanes at intersections are summarized.In order to determine the critical condition of traffic flow,this paper studies the left-turn traffic and straight-ahead traffic.Taking the average delay of vehicles before and after setting up variable approach lanes as the objective,the model of equal-vehicle average delay is constructed.The trial value method is used to solve the model,then the proportional threshold of left-turn traffic can be obtained.The feasibility of the model is verified by an example.Finally,the control method of the variable approach lane at signalized intersection is studied.An adaptive control system is proposed in combination with signal timing optimization under the premise of setting variable approach lanes at intersections.The system consists of three modules: traffic condition prediction,lane function decision and signal coordination control.In this paper,real-time traffic data,including flow,speed and occupancy rate,are obtained by setting detector at intersections.Fuzzy c-means clustering algorithm is used to analyze the sample clustering and traffic state identification,and Random Forest is used to predict the short-term traffic state.On this basis,the lane function switching decision is made,and the transition time of vehicles when the lane function changes is considered at the same time.A pre-signal control method is proposed to realize the signal coordination control of the variable steering lane with the timing optimization of the main signal.Taking an urban intersection as an example,this paper uses simulation methods to obtain real-time data and carry out adaptive control,and analyzes the intersection optimization effect,verifying the effectiveness and practical application of the system.