The equilibrium model for congested traffic assignment in road networks

To overcome the weakness of using the traditional model for static traffic assignment in analyzing traffic assignment problems in congested road networks, equilibrium models for static congested traffic flow assignment in road networks are presented in this paper. First, based on the characteristics of the traffic flow in congested link, properties of the impedance function of congested road links were analyzed, which satisified that the traffic flow rates would decrease with increasing vehicles in congested links. Then, the route choice behavior in congested road networks was investigated. The equilibrium principles and mathematical models of user equilibrium and system optimum were proposed in the static form. Additionally, it was proved that the proposed user equilibrium model was equivalent to the user equilibrium principle and had a unique solution. Finally, the iterative weighted algorithm was given to solve the proposed user equilibrium model. The comparison between the proposed model and the tranditional traffic assignment was made on the basis of a simple example. Results show that the proposed user equilibrium and the system optimum models could reasonably describe the congested user equilibrium and system optimum principles, and the user equilibrium model could reasonably describe the real passing flow rate in the congested state. The proposed models could be applied to partial congested areas and used as one of the core parts of the semi-congested traffic assignment model. © 2019, Editorial Board of Journal of Harbin Institute of Technology. All right reserved.