Statistical analysis of bus transportation networks for four largest cities in Turkey

Network properties for public bus transportation networks (BTNs) of four largest cities (İstanbul, İzmir, Ankara, Bursa) in Turkey have been analyzed under C-, L- and P-Space topologies. Node degree distributions are shown to follow power-law distribution indicating scale-free nature of the networks. Furthermore, the networks have been growing preferentially with the exception of Bursa. Degree-degree correlations of nodes were studied in assortativity. The networks have small shortest-path values. For example, in İstanbul the maximum shortest path was found to be 4 in C-Space meaning that one needs at most 4 transfers to reach any point in the network. Correlation between mean shortest path lengths and nodes of given degrees of single end nodes are shown to follow power-law in L-Space. Degree, eigenvector, closeness, and betweenness centralities of nodes were calculated, and correlation between mean centrality values and degree were well described by power-law. Thus, in summary, BTNs show small-world and scale-free properties. We also investigated the impacts of two recent projects, Metrobüs and the Third Bosphorus Bridge, on bus network properties in İstanbul.