Research On Traffic Capacity And Signal Timing Optimization Of Heavy Traffic Highway

Highway signalized intersection is the key of regional highway network,which plays an important role in directing traffic flow in all directions.With the continuous increase of the number and tonnage of trucks in China,the traffic congestion problem at signalized intersection of heavy traffic highway is becoming more and more serious.In view of the above problems,this paper analyzes the characteristics of traffic flow at the signalized intersection of heavy traffic highway based on the measured data,proposes the calculation methods of passenger car equivalents and start-up loss time at the signalized intersection of heavy traffic highway,establishes the capacity model,and carries out the optimization design of intersection signal timing finally.The main contents are as follows:(1)According to the requirement of traffic composition and traffic flow,this paper selects several signal intersections of heavy traffic highway to investigate and analyzes the characteristics of traffic flow.The results show that because of the large proportion of medium and heavy vehicles,the vehicles at the intersection accelerate very slowly during the green light.Traffic is constantly accelerating and it is almost impossible to reach a steady speed during green lights.And in the following process,the time from the tail of front vehicle to the head of rear vehicle increases significantly with the increase of the vehicle type,and the difference is not obvious with the change of the vehicle speed.(2)Based on the characteristics of traffic flow at signalized intersection of heavy traffic highway,this paper proposes the calculation methods of passenger car equivalent under different running stages respectively.On the basis of capacity calculation method,the calculation method of passenger car equivalent in acceleration stage at signalized intersection of heavy traffic highway is proposed.Based on the time headway method,the calculation method of passenger car equivalent in the stable stage at signalized intersection of heavy traffic highway is proposed.The result shows that there is no significant difference in passenger car equivalent between acceleration stage and stable stage at signalized intersection of heavy traffic highway,and the passenger car equivalent values are significantly lower than that at basic highway section.(3)Based on the analysis results of traffic flow characteristics,this paper proposes the calculation method of signal intersection start-up loss time when single vehicle type is passing and obtains the calculation method of start-up loss time under various vehicle types by means of conversion according to vehicle proportion.Combined with the calculation method of start-up loss time and saturated flow rate model,the capacity model at signal intersection of heavy traffic highway is established.(4)This paper selects average delay,parking rate and traffic capacity as performance indicators to establish a multi-objective timing optimization model of signalized intersections and uses constant step search method to solve the model.By comparing the performance indexes of the multi-objective timing optimization scheme and the current situation timing scheme,the results show that the performance indexes of the intersection have been improved to varying degrees after optimization,with the average delay reduced by 0.86 %,the parking rate reduced by 5.00 %,and the traffic capacity increased by 8.21 %.In addition,the setting of all-red time reduces traffic conflicts and improves the safety of intersections.The overall operation benefit of the intersection has been significantly improved.