Research On Structural Characteristics And Robustness Of Shaanxi Freeway Based On Complex Network Theory

In recent years,with the continuous improvement of the road network,the freeway has gradually become networked and complicated.At the same time,the constant occurrence of various emergencies also sets higher demands on the connectivity of the road network.Complex network theory provides a new methodology for systematically analyzing freeway topology and robustness.System science believes that the structure determines the function,and the freeway as a typical complex network,its topology has an important impact on the accessibility of the regional road network,and its robustness is also of great significance to the safe operation of road network under emergencies.This paper takes the Shaanxi Freeway Network which has been built and is under construction until October 2018 as the research object.The author introduces the complex network theory,and constructs two road network models based on the original mapping method and the dual mapping method.Furthermore,based on those two different road network models,the complex structure characteristics of the freeway network in Shaanxi Province are analyzed from six indicators: node degree,average path length,clustering coefficient,closeness centrality,betweenness and network efficiency.The analysis results show hat the freeway network in Shaanxi Province is a scale-free network,not a small world network;the distribution of node degrees and betweenness centrality in the network is uneven,only a few nodes with high node degree and big betweenness play a key role in the road network.The meaning of freeway robustness is the resistance performance of the road network to various interferences from the outside world.The robustness reflects the fault tolerance of the road network and is one of the key indicators to measure the overall performance of the freeway network structure.In this paper,the indicators applicable to the robustness of freeway networks are proposed: the relative value of network efficiency and the relative size of the largest connected subgraph.In order to clarify the change law of freeway robustness in Shaanxi Province,two kinds of interference modes,“random interference” and “directional interference”,were designed.The robustness of different interference strategies was simulated by R software.The experimental results show that the freeway network in Shaanxi shows good robustness to random interference,but the robustness to directional interference is poor;The impact of different nodes on the overall performance of road network robustness is very different.The network height depends on the top 30% of the nodes of "betweenness" and "node degree";based on different interference strategies,the robustness of the freeway network in Shaanxi Province is ranked as follows: robustness under random interference > Robustness under directional interference based on betweenness > Robustness under directional interference based on nodal degree.Finally,the paper puts forward the network efficiency change value as the quantitative index of the key nodes and key road segments of the road network,and compares the index with the original classical theory.The results show that there is a positive correlation between the two indicators,indicating that the indicator is effective and reasonable.Finally,some improvement suggestions are put forward for improivng Shaanxi freeway Network operational reliability.