On applying Petri nets to determine optimal offsets for coordinated traffic light timings

Significant classes of transportation systems can be represented by Petri net models. In this paper, Petri nets are applied to provide a modular representation of urban traffic systems regulated by signalized intersections. The basic idea is to consider such systems to be composed of elementary structural components, namely, intersections and road stretches. In order to describe thoroughly the movement of vehicles in the traffic network, a microscopic representation is adopted and realized via timed Petri nets. An interesting feature of the designed model consists in the possibility of representing the offsets among different traffic light cycles as embedded in the structure of the model itself. In turn, that allows us to simply implement the coordination among traffic light timings, which facilitates the description and solution of the relevant optimization problems.