Analyzing Robustness Of Urban Road Network Based On Complex Networks

The most important transport problems are often related to urban areas and take place when transport systems, for a variety of reasons, cannot satisfy the numerous requirements of urban mobility. Urban productivity is highly dependent on the efficiency of its transport system to move labor, consumers and freight between multiple origins and destinations. The city road system, as well as other complex systems, can be modeled as networks. Studies investigating the relationship between network structure and functionality provide a novel perspective to investigate the robustness of a city road network by analyzing its structure.In this paper,the robustness of city road network is analysed at different spatial scales based on the theory of complex network. First, the basic theory of complex network models and its statistical characteristics are introduced. Then road networks are modeled at three different granularities:segment-based,stroke-based and community-based model to investigate the response of road networks under punctiform, linear and zonal traffic interruptions respectively. Third, two types of performance, i.e., efficiency behavior and fragmental fraction, are used to evaluate the robustness of city road networks under attack. Finally, the road networks of Urumqi are modeled by the method of dual approach and its structural robustness are evaluated at different granularities.In this study, the statistical characteristics of Urumqi urban road network at different granularities are calculated based on the open-source toolkit-Network X. The results show that Urumqi road network have large clustering coefficient and smaller average path length under the spatial scales of segment, namely, and community. Meanwhile, the namely-scale road network also obeys power law distribution and its power-law index is 1.43. Therefore, it is a typical scale-free network. However, the road network of segment and community do not have the smiliar characteristics and they are not scale-free networks. All in all, the namely-based road network of Urumqi has the dual characteristics of small-world and scale-free, while the segment-based and community-based road networks of Urumqi only has a small world characteristics.To uncover whether and how the structural importance characters affect the robustness of the road networks, this study generates two attack strategies. The robustness of Urumqi road network at different spatial scales are compared under the strategies of random attack and deliberate attack. The performances of city road networks under attacks are consistent in different cities due to the similarity in their topological structures but differ by granularity because city road networks modeled at different granularities have different topological structures.