The small-world hierarchical modularity of urban subway networks

We present the empirical investigation results on the urban subway networks in China, the empirical results show that all the urban subway networks have high clustering coefficient and small character path length, which exhibit small-world behavior, otherwise, these networks are hierarchically organized by some motifs, which are all the globally coupled networks. To explain these results, we introduce a small-world hierarchical model which is in good agreement with the empirical results, in addition, this model can explain the evolutionary procedure of other networks, such as the urban bus transport networks or the film actor networks.