Intercity express bus flow in Korea and its network analysis

We investigated the express bus flow in Korea and its network topology. By using a gravity type model, we found that the bus flow between cities depends on the square root of the product of the population size of city A and the population size of city B. On the other hand, the total bus flow of a city depends on only its population size. These different dependences on population originate from the network property of the express bus network.