Research On The Control Method Of The Intersection Downstream Of Urban Elevated Off Ramp

City elevated expressway as an important part of city traffic,the "can't in or out" traffic problem of elevated expressway is increasingly frequent,under the increasingly serious trend of urban traffic congestion.The off-ramp area congestion is one of the more prominent problems,especially when the ramp connected to the downstream intersection,the queue of ramp and intersection approaches will spill out to elevated and upstream intersection under the condition of oversaturated traffic demand.Therefore,it is very important to study the signal control optimization of ramp junction,which is helpful to alleviate the traffic congestion of the ramp and downstream intersection.In order to relieve the "can't out" problem of the elevated,the traffic flow model and signal control optimization method of the exit ramp and downstream intersection is studied in this paper.The specific research works are shown as follows:Firstly,the researches and applications of control method of expressway on and off ramp and oversaturated intersection were analyzed and summarized.The forms of the exit ramp and the traffic organization of ramp junction area were classified in this paper,and the influence of different weaving flow ratio on the weaving area was studied with VISSIM simulation.According to the weaving problem caused by the lane changing to different destinations of off-ramp vehicles,the transmission probability to adjacent cells has taken the discretionary lane-changing and mandatory lane-changing maneuvers into consideration.At the same time,the verification model of stranded vehicle in virtual cellular is introduced,and the improved cell transmission model of the weaving area is constructed.The experiments show that the model can simulate the formation and dissipation of queuing.The control model of the terminal cell at the entrance combing with the signal phase was established based on the improved CTM,in which the signal control model is integrated with the transmission of traffic flow and the renewal of the cell state.The signal dynamic optimization model is built based on the weighted average delay which is obtained from the improved CTM,combined with genetic algorithm.Considering the different saturation of the intersection at different time,the CTM and real time dynamic optimal model of traffic signal were established in MATLAB,and the network state is updated according to the optimal traffic signal timing.Finally,the evening peak traffic data of Niushikou off-ramp in Chengdu Second Ring Elevated Expressway was used to validate the optimal model,the results show that the model has good control effect on this intersections of unsaturated or oversaturated state.