Self-Healing Networks - Gridlock Prevention with Capacity Regulating Traffic Lights

The capacity of a road network is predetermined by the green times at its intersections. As these are typically designed for expected traffic demands, spontaneous demand peaks or lane blockings will likely lead to congestion spreading over larger parts of the network. We show that gridlock effects can be prevented by a capacity regulating traffic light control designed to avoid critical spill-backs and to distribute traffic among remaining road capacities. The idea is that traffic lights do not serve more vehicles than subsequent roads can accommodate. The regulation of inflow in over-saturated road segments with shorter green times implies that remaining turning directions can be served with longer green times. In consequence, defective parts of the network are relieved from some traffic, whereas remaining capacities on surrounding roads are made available by promoting alternative routes. In this way, a redistribution of traffic on bypass routes goes hand in hand with an instantaneous reallocation of green times.