Research on the quasi-equilibrium assignment method considering signal intersection delay and link interaction

In this paper, taking traffic signal delay and link interaction into account, a bi-level system optimization traffic flow equilibrium assignment model is presented with the aim of minimizing total travel time of the network in first-level while ensuring equal saturation of each link in the second level. In the model, the link cost contains travel time between two intersections plus signal delay at the downstream intersection. To make the model easily and effectively be solved, the paper presents a quasi equilibrium assignment algorithm, in which the calculation of equilibrium link flows is integrated with measurement of congestion considering both link and intersection. The algorithm may not have enough ability to make the congested traffic flow become smooth immediately, but the dissemination of traffic guidance information (via broadcast or in-vehicle equipment) to divert oversaturated traffic volume under certain traffic demand at consecutive intervals. At the same time, the optimal traffic signal timing is designed to allow the persistent adjustment in response to traffic flow variations. Finally, a computational experiment is carried out on a small network and using realistic intersection delay functions in order to test the behavior of the model.