GENERALIZED COMBINATION METHOD FOR AREA TRAFFIC CONTROL

A simple generalization of the British combination method is given for optimizing offsets in synchronized, traffic- signal networks of a general structure. The method then is used in a recursive procedure to determine values for the offsets along each street, the splits of green time at each intersections of the network, and the common cycle time of the controlled area. The signals' cost to travelers is evaluated as the sum of 2 components: one associated with a deterministic traffic-flow model and the other associated with randomness in traffic behavior. The deterministic component is a function of the coordination among the signals in the network and generally increases with cycle length. The stochastic component depends on the expected overflow queue at each traffic light and decreases with cycle length. It is shown that optimal settings are determined at the equilibrium point of minimum total cost resulting from the combined effect of the 2 components.