An Equilibrium System Model and Algorithms of the Urban Traffic Congestion Problem

This paper proposes an equilibrium system model for analyzing urban traffic congestion problems. According to the traffic equilibrium theory, each link on the traffic network has an optimal capacity to achieve equilibrium, with matching grade and settings. Traffic congestion occurs when capacity appears to decrease, when the road's capacity is less than the traffic demands. In order to find out all the congestion links on the network, a hierarchical model is established according to the network structure and road category scale; it includes the main roads and the branches. Comparing the road's optimal matching capacity and the real capacity, we computed the difference. For each link, if the optimal matching capacity was greater than the real capacity, it would need to be widened or reconstructed. For the whole network, the matching degree reflects the compatibility of the road supply and transportation demand. The traffic congestion diagnostic process should encompass the whole network down to a partial road; the bottlenecks would be a indicated by point, a line, or even an area, where congestion occurs. In the paper, we discuss the measurement of the congestion, the congestion degree on the link and the matching degree of the network. The congestion degree shows the severity of the problem, while the matching degree explains the efficiency of the network. This model describes the conflict between road supply and transportation demand, from macrocosm to microcosm. It, moreover, finds the discrepancy in the road network, and gives some reference for the urban transportation infrastructure construction and planning.