Optimal mode of each intersection in a congested road network

This paper proposes a model to investigate the mode (signalized, one-way separation overpass or two-way separation overpass) of each intersection in a congested road network. In the proposed model, the interaction between intersection modes and travelers´ route choices is explicitly considered, and the traffic signal parameters (signal cycle time, green time) and vehicle delays at the intersections are endogenously determined by empirical formulae. The proposed model is formulated as a 0-1 integer bi-level programming problem. The upper level of the model aims to minimize total network cost (including travel cost and construction cost) by determining the optimal mode of each intersection in the network, while the lower level is a deterministic network user equilibrium problem that considers both link travel time and intersection delay. A genetic algorithm based solution approach is developed to solve the proposed model. A numerical example is given to show the capability of the proposed solution algorithm in seeking the optimal intersection modes, and the importance of reasonably choosing the intersection modes in improving the performance of transportation system in terms of total cost, and the order to construct the overpasses.