Research On Emergency Evacuation Area Extraction And Network Connectivity Evaluation Method Based On Complex Network

As we all know, urban traffic congestion has been caused seriously by both various types of large-scale activities held and a variety of major disasters occurred frequently in many cities in China. When a lot of traffic flow is gathered in a short time and small space, massive traffic jams, regional traffic paralysis can happen easily without strict prevention and control measures. With respect to the effects caused by emergencies, emergency evacuation needs to be conducted for the emergency scopes, While a prerequisite for the implementation of the control strategy of the evacuation is to identify emergency evacuation area. Generally, qualitative division method is adopted to extraction of emergency evacuation area, which is based on experience judgment, lacks the necessary theoretical basis, as well as being difficult to use for traffic managers.In this paper, the method of emergency evacuation area extraction and connectivity evaluation of the regional road network were studied in order to solve the problem of extracting the emergency evacuation area through community structure theory.Firstly, the network traffic characteristics of road traffic under emergency was analyzed, of which is as a basis to define two principles of division. That is, the road network under emergency was divided into emergency evacuation area and security zone.Secondly, the concept of a complex network of community structure and modularity was introduced to this paper. Then common structure extraction methods in community were compared and analyzed. Ultimately emergency evacuation area was extracted using the W-H algorithm selected, and deficiencies of the extraction process were analyzed.As for issues the W-H algorithm exists that threshold aliquots and end nodes can not be determined, module strength model based on the network topology and based on travel time was established.Then W-H algorithm was improved from the three aspects from the search of end node, the selection of resistance, determination of voltage threshold. The extraction method of emergency evacuation region were proposed based on maximizing the strength of the module. At last, simulation environment was built based on road network data from Shenyang city using the Trans Modeler software. Method validation and comparative analysis also were presented in this paper.Connectivity evaluation method was proposed based on the largest road network connectivity subgraph with respect to evaluation of the effect of the implementation of transport evacuation strategies after extraction of emergency evacuation area. Firstly, by the relationship between the actual travel time versus time threshold introduced and from the traveler’s point of view, sections of the on-off state was determined, and then network connectivity was calculated using the relative sizes of maximal connected subgraph before and after road network fails. Besides, processes and algorithms of determination of road connectivity and calculation of network connectivity were showed. Finally, simulation results from Trans Modeler were verified the effectiveness of the algorithm. The emergency evacuation area was evaluated by exploiting the road network connectivity. Ultimately verification was carried out using above methods.