Improved Optimization And Coordinated Control On Ramp Diversion Of Half Cloverleaf Interchange

At this stage,with the long construction period,complex conditions and the main line interweaving conflict becoming more and more serious,half cloverleaf interchange has gradually become the best choice for urban interchange construction.As one of the four limb cloverleaf interchange,half cloverleaf interchange not only has the advantages of unimpeded main road,simplified main line signs,less land and engineering costs,but also is suitable for the intersection of main roads and secondary roads,strict restrictions on surface features or staged construction.For the existing half cloverleaf interchange in various cities,most of the main line off ramps are designed as single ramp.If you want to realize the function of intercommunication,the vehicle must first drive into the secondary main road through a single ramp,and then realize intercommunication by turning around at the next intersection.However,this method is only suitable for the case of small overall traffic flow.When the traffic flow is large,not only the capacity of single ramp is easy to be saturated,but also the connection area,weaving area and intersection of secondary roads will be seriously blocked.In order to solve this problem,this paper proposes to set additional left-turn ramp at the main exit ramp by using ramp diversion method.This way can make the vehicle turn left directly at the entrance of the secondary trunk road,improve the traffic efficiency and relieve the pressure of the secondary trunk road.However,due to the conflict zone,this method is only mentioned in theory and has not been used in practice.How to ensure the integrity of the off ramp traffic flow and the overall road efficiency has become the key to further research.Aiming at the problem of conflict area in half cloverleaf interchange,this paper takes a city interchange as an example,based on the analysis of traffic characteristics in conflict area,studies the critical point and specific setting method of signal setting;secondly,the single ramp and shunt ramp are evaluated by Vissim simulation software,and the advantages of ramp diversionare pointed out.Finally,the fixed signal timing of shunt ramp is optimized by Synchro traffic signal software,the necessity of coordinated control of main line is verified by evaluation.In this paper,the specific solutions to the conflict area of half cloverleaf interchange are given,which can improve the design and traffic management of the line.