A two-class traffic control scheme for reducing congestion and improving safety in freeway systems

The definition of a new control scheme for freeway traffic systems is the objective of the present paper. The main innovative aspect of this work stands in the fact that, besides considering the reduction of traffic congestion, also safety-related aspects are explicitly taken into account in the formulation of the control problem. More specifically, two different performance indexes including a relation between the number of accidents and the traffic density in a freeway stretch are defined. The solution of the control problem is sought by applying a derivative-free procedure in which two phases are sequentially adopted: A global search carried out through a specific version of the Simulated Annealing algorithm, and a local search performed by an algorithm chosen within an open-source library for nonlinear optimization. Some numerical results are reported in the paper to compare the two control functions and to verify the effectiveness of the proposed approach.