Optimal offsets for traffic signal systems in urban networks

The paper proposes a binary integer programming model for the computation of optimal traffic signal offsets for an urban road network. The basic theoretical assumptions for the computation of delay on the network are those employed by the main models developed during the last few years. The set of input data coincides with that needed for the Combination Method and its extensions. The model is solved through a branch-and-backtrack method and allows the obtaining of optimal offsets for condensable or uncondensable networks without introducing any special assumption on delay-offset functions, contrary to what occurs within other mathematical programming formulations of the problem. A reduced memory dimension is required by the developed algorithm, which promptly supplies during the computation better and better sub-optimal solutions, very interesting in view of the possible application of the method to real-time control problems. The tests performed show that the method can be applied to networks of practical size.