Exploring the Complexity of Urban Bus Network, a Perspective from the Bus Frequency Data

The topology and properties of public transport networks (PTNs) are an important focus of public transportation planning, but the bus frequency data is rarely considered in the study of PTN. This paper builds bus stop network and bus transit network with a new perspective: time-varying bus lines’ frequency. Based on these two types of network model, we investigate Nanjing PTN, analyzing the static topological properties and time-varying characteristics of it. Both networks, especially bus stop network, are small-world networks. The weighted bus stop network has 1581 nodes and 2355 edges. The weighted bus transit network has 50352 edges, which shows that the average transfer time of Nanjing PTN is 1.9. This network also reveals that although the average waiting time varies by 8.9 min at the most, the travel plan of passengers at different times does not change significantly. 92% of the nodes have no significant change in the betweenness centrality at different times. We take bus frequency into the consideration of evaluation and optimization of PTN, and it is exemplified that the bus frequency data plays an important role in it.