Statistical description of the constructed networks.

means the network of Beijing public transport system; means the network without rail transit stations; means the rail transit network; means the randomized degree-preserving network of . N is the number of nodes; m is the number of edges; I is the median of in-degrees; O is the median of out-degrees; p is averaged shortest path distance; c is clustering coefficient; r is assortative coefficient. Note that the sum of N of and is larger than the node number of because there are two stations shared by and .