Multi-intersection two-way traffic light control with blocking using infinitesimal perturbation analysis

We address the traffic light control problem for multiple intersections in tandem by viewing it as a stochastic hybrid system and developing a Stochastic Flow Model (SFM) for it. Our model includes roads with two-way traffic and with finite vehicle capacity in-between intersections, which may lead to additional delays due to traffic blocking. Using Infinitesimal Perturbation Analysis (IPA), we derive on-line gradient estimates of an average traffic congestion metric with respect to the controllable green and red cycle lengths. The estimators are used to iteratively adjust light cycle lengths to improve performance and, in conjunction with a standard gradient-based algorithm, to obtain optimal values which adapt to changing traffic conditions. Simulation results are included to illustrate the approach.