Congestion and efficiency in complex traffic and transportation networks

This paper investigates the congestion and efficiency in complex traffic and transportation networks. Effects of different distributions of capacity and origin-destination traffic demand on the degree of congestion and efficiency are explored in different network topologies including scale-free networks, random networks and small-world networks. According to the increase of average traffic demand, the transition from free flow state to congested state is analyzed. For easy comparison, we discuss the reciprocal of the congestion degree, which is defined as the network unobstructedness. A linear relation between the degree of unobstructedness and efficiency in different networks is uncovered, and the linear proportional coefficients are different in scale-free networks, random networks and small-world networks. These coefficients can also be used to describe the different transport performance in different networks.