Self-control of traffic lights and vehicle flows in urban road networks

Abstract

Based on fluid-dynamic and many-particle (car-following) simulations of traffic flows in(urban) networks, we study the problem of coordinating incompatible traffic flows atintersections. Inspired by the observation of self-organized oscillations of pedestrian flows atbottlenecks, we propose a self-organization approach to traffic light control. The problemcan be treated as a multi-agent problem with interactions between vehicles and trafficlights. Specifically, our approach assumes a priority-based control of traffic lights by thevehicle flows themselves, taking into account short-sighted anticipation of vehicle flows andplatoons. The considered local interactions lead to emergent coordination patterns such as‘green waves’ and achieve an efficient, decentralized traffic light control. Whilethe proposed self-control adapts flexibly to local flow conditions and often leadsto non-cyclical switching patterns with changing service sequences of differenttraffic flows, an almost periodic service may evolve under certain conditions andsuggests the existence of a spontaneous synchronization of traffic lights despite thevarying delays due to variable vehicle queues and travel times. The self-organizedtraffic light control is based on an optimization and a stabilization rule, each ofwhich performs poorly at high utilizations of the road network, while their propercombination reaches a superior performance. The result is a considerable reductionnot only in the average travel times, but also of their variation. Similar controlapproaches could be applied to the coordination of logistic and production processes.