Research On Control Method Of Urban Expressway Exit Ramp

With the continuous increase of car ownership in major cities in China,the urban traffic demand growth has been growing more than the traffic supply,and the traffic congestion problem has been becoming more and more serious.The urban expressway has been the main skeleton and aorta of the whole urban road network,people's travel efficiency and urban economic development have been directly affected by the quality of their services.In the early morning and evening peak periods of urban traffic,the traffic congestion had been easily formed as the exit-ramp vehicles and ground vehicles converge on the urban expressway exit-ramp,which had leaded to the upstream traffic flow been larger than the traffic capacity at the Congestion section,resulting in traffic congestion at the upstream of the traffic intersection.When the backlog of queuing vehicles on the ramp had been traced back to the expressway,the efficiency of the main expressway will be reduced,causing adverse effects.If no effective traffic signal control methods have been adopted to evacuate the traffic congestion at this time,the exit ramp of the expressway will be blocked,and the "domino phenomenon have been caused by the congestion of the expressway,which can be traced back several kilometers and spread to cover a series of exit ramps of the expressway,the relevant road network will be paralyzed.Therefore,the topic of effective traffic planning design and signal control for the expressway exit-ramp traffic congestion have been worthy of study,and it also has important practical significance.This thesis studies the congestion of exit ramp traffic.Firstly,we put forward the basic meaning of traffic congestion,and analyzed the influencing factors of traffic congestion near export ramps,optimized including the exit ramp setting,the design of Interlaced section,traffic organization and signal control.Secondly,we designed the initial parameters of single-point actuated control at the exit ramp of expressway junction intersection,and proposed signal control strategies such as key phase green time extension and phase phase sequence optimization.Then,when the exit ramp meets the intersection and the downstream intersection is also saturated or supersaturated,the intersection adopts the maximum optimization model based on the downstream traffic capacity limit bottleneck intersection capacity for evacuation,and control the traffic demand by the interval release strategy for the auxiliary road vehicles,When the congestion section is in the state of over saturation,the green time of upstream intersections should be appropriately adjusted to make the traffic demand less than the traffic supply,so as to evacuate the queuing vehicles.Finally,taking the intersection of the National—XiongChu Avenue as an example,proposed the optimization scheme from the aspects of traffic design traffic organization,traffic management and control,etc.Under the condition of traffic congestion at the early peak intersection,we used the single-point actuated control strategy and coordinated control strategy are to simulate the traffic through VISSIM.The results show that the proposed control strategy can effectively utilize the space-time resources of the road network near the exit ramp to prevent the export ramp lock and achieved the expected control effect.