Research On Emergency Facility Location Based On The Node Importance Of Urban Traffic Network

With the expansion of city scale and the complexity of its functions,the city faces the increasing risk of emergencies.The urban traffic network structure is complex,and it is easy to be affected in emergencies.Especially,if some important intersections or stations fail to work,improper emergency disposal will lead to local or even global paralysis of the traffic network,which brings serious harm to the urban operation and the production and living order,and causes great impact and threat to the safety of life and property.The reasonable layout of emergency service facilities providing emergency resources is the key to effectively deal with emergencies and plays an important role in reducing the emergency impact on traffic network.Therefore,it is of significance to study characteristics of urban traffic network and the scientific and reasonable layout of emergency service facilities,which can improve the capability of urban traffic system to resist emergencies and ensure the city safety.This paper conducted the research on emergency service facility location based on urban traffic network node importance,which analyzed the node importance of traffic network by using complex network theory and strengthened the protection and emergency support for important nodes by introducing the node importance evaluation results into the location decision.The main works are as follows:(1)The emergency characteristics and their impacts on urban traffic network were analyzed,and the function orientation of emergency service facility and the factors to be considered in the location were given.Combined with the complex network theory,the topology information of urban traffic network was extracted based on the data of points of interest(POI).Considering the actual collaborative development of different traffic networks,the urban traffic network model of road traffic and rail transit was constructed with intersections or stations as nodes and roads or lines as edges from a compound perspective,aiming to improve the overall efficiency and capability of urban traffic emergency system.(2)From the network structure characteristics,vulnerability and social economy,an evaluation index system for urban traffic network node importance was established.Combining with self-organizing feature map neural network,hierarchical clustering and K-means clustering,a hybrid clustering method was proposed,aiming to integrate multi-attribute features to cluster and differentiate the node importance.Taking the traffic network of Shijiazhuang city as an example,four importance levels of nodes and their spatial distribution were concluded,and the values of comprehensive importance were identified.The rationality of the importance evaluation results was also verified,and the applicability and effectiveness of the proposed evaluation system and method were thus demonstrated.(3)In order to protect the nodes and their adjacent areas through the reasonable location of emergency service facilities,the node importance and its evaluation level were introduced to determine the value weight coefficient of nodes,the parameter of coverage function and the multi-level multiple coverage number in the modeling of emergency service facility location problem(ESFLP).From the perspective of node importance,a multi-objective programming of ESFLP was established with the goals of minimum cost,maximum efficiency and optimal coverage.Two non-dominated sorting genetic algorithms(NSGAs),i.e.,NSGA-II and NSGA-III,were developed and improved to adapt the proposed model.The numerical experiment showed that the NSGA-III outperforms the NSGA-II in the ESFLP of multi-objective decision.(4)Taking the Shijiazhuang traffic network as an example,the Pareto solution of ESFLP based on the node importance of urban traffic network was calculated by the improved NSGA-III,and the final location scheme was given according to the preference of decision-makers.Compared with the scheme without considering the node importance,the results showed that the scheme considering the node importance improves the coverage times and emergency efficiency of important nodes and more accords with the actual needs,which thus verify the effectiveness of the model and algorithm.The study is expected to shed light on the decision of urban traffic emergency management.