| With the dramatic increase in the population of urban residents,the traffic pressure on urban road networks is increasing,and the traffic management department faces enormous challenges.In the event of a devastating emergency,the capacity of certain sections of the original road network will drop rapidly or even falter.However,the surge in personnel and vehicles that need to be evacuated will break the balance between supply and demand of the original road network,and the existing traffic organizations cannot meet the evacuation needs of the disaster-stricken road network under emergencies.At this time,it is necessary to reorganize the traffic network in a short period of time,improve the capacity of the road network to accommodate the traffic flow,shorten the evacuation time,and reduce losses.Since the reverse lane can increase the traffic capacity in a specific direction in a short time,and has the advantages that other organization methods cannot match,the organization method of setting the reverse lane can greatly improve the evacuation efficiency and reduce the harm that emergencies bring to the transportation system.Based on the research status at home and abroad,this paper expounds the selection methods of reverse road sections in the current emergency evacuation strategy,and analyzes the characteristics of urban road network traffic flow,emergency rescue characteristics and traffic emergency evacuation strategies when affected by unexpected events.Combined with the advantages and disadvantages of the reverse lane in practical applications and the influencing factors in the setting process,the emergency evacuation organization mode of the urban road network under the emergency conditions is studied.Firstly,through the network optimization method,the real city evacuation network is abstracted into a directed network capable of mathematical calculation.Combined with the classic maximum flow key edge model,the reverse lane selection problem is transformed into the key edge search problem in the network.On this basis,the maximum flow-increasing key edge model is established to meet the requirements of improving the network evacuation capability.The key edges of the expansion are defined and the maximum flow is calculated,and the corresponding algorithm is improved.Secondly,considering the maximum flow requirement for reaching the evacuation end point at any time during the actual evacuation process,the global maximum flow model is established and the dynamic expansion key edge is defined.In the event of an emergency,the characteristics of the passage capacity change over time are obvious,in the past,when scholars studied the problem of reverse road segment selection,most of the established maximum flow key edge models ignored this actual situation,which led to the deviation of the obtained reverse road segment selection scheme from the actual situation.Considering theactual situation that the traffic capacity of the road segment in the evacuation network changes with time,the global maximum flow algorithm is improved accordingly,so that it can calculate the actual dynamic network.Finally,taking the explosion event of Lanzhou Petrochemical Synthetic Rubber Factory as an example,the global maximum flow model is established and calculated under the condition that the traffic capacity of the road section is constant and the traffic capacity changes with time,and the corresponding reverse road segment selection is obtained under two different situations.The scheme compares and analyzes the differences between the two schemes,and then demonstrates that the global maximum flow model has good effects.The proposed algorithm is also feasible. |
