Effects of road network structure on the performance of urban traffic systems

Abstract Urban traffic system is important for the convenience and efficiency of people’s daily life. The understanding of inter-relations between urban street network and traffic flow can help the planning process of urban systems. Based on cellular automata modelling, this paper studies the influence of aspect ratio of a rectangular urban network on the dynamics of traffic system. The performance of road network is examined with the Macroscopic Fundamental Diagram (MFD). The maximal arrival rate and the critical density of congestion of MFD are investigated as two main indicators for system performance. Under the closed boundary condition, the square network shows the maximum arrival rate, but with a relatively lower critical density of congestion. With the increase of aspect ratio, the arrival rate decreases, while the critical congestion density increases. The phenomena can be explained by the vehicle distribution in the network, the left-turning and U-turning demand, and the average travel distance.