Research On Urban Expressway Emergency Evacuation Under The State Of Emergency

With the continuous development of urban expressway system,the urban road network structure is increasingly complicated and traffic demand is increasing,in addition to frequent traffic congestion,the main reason of urban expressway traffic delays unpredictable emergencies is caused by occasional traffic congestion.At present,the study of emergency evacuation for urban expressway emergencies is mainly to reduce the traffic demand in the upper reaches of the emergency location and only evacuate queuing vehicles from the upstream of emergency location,without taking into account the incident on the regional road network traffic Influence and diffusion effect,evacuation effect is poor.Therefore,it is necessary to study the emergency evacuation method of urban expressway emergencies based on the duration and influence range of emergencies,making better the efficiency of emergency evacuation of urban expressway emergency.The characteristics of urban expressway emergencies are analyzed,and the emergencies of expressway emergencies are classified according to the influence range of emergencies.The study take Yatai street expressway in Changchun city as an example to analyze the traffic of urban expressway emergencies characteristics and diffusion rules,from the point delay,line delay and face delay in three stages;Secondly,determined the method of the scope with expressway emergency,the duration of the incident is divided into delay time and recovery time.The VISSIM software is used to analyze the relationship between delay time and influence range of the incident,to get the relationship between average travel time of the expressway,average travel time of the main road,delay time of the expressway and delay time of emergency.Based on the traffic wave model,the maximum queuing length and the emergency recovery time caused by the emergency of a certain delay time are compared with the simulation results to prove the validity of the model.Then,the basic assumptions of the optimal control model of urban expressway area are given,and traffic demand model and traffic supply model are constructed.The traffic capacity and the traffic demand variance and the optimal control model of the evacuation performance index are established.The objective function is the intersection of each trunk road and the expressway which is to improve the traffic capacity of the expressway and ensure the smoothness of the main road,getting performance index and minimum of incident area,the optimal upstream and downstream ramp rate and the signal crossing phase of emergency upstream.Finally,the design flow chart of emergency evacuation method for urban expressway emergencies is given,and the express route of Yatai street is analyzed as an example.The concrete application mode of emergency evacuation method is expounded and the method of evacuation effect to evaluate.The results show that the total queuing length of the regional road network,the total travel time of the regional road network and the travel delay time of the expressway are obviously reduced after the implementation of the emergency route evacuation method of the urban expressway emergencies.Flow efficiency is improved,evacuation effect is obvious.