Method for controlling traffic flow

Abstract

An intersection control system is described which coordinates a plurality of intersections each of which is responsive to local requests for service. Traffic control coordination is accomplished between a plurality of intersections by providing for each intersection an Intersection Control Unit capable of response to local demand and a variety of permitted phase conditions, and by providing a processing unit for each group of intersections (a Network Processing Unit) which determines the permitted phase conditions at the intersections within constraints of system-wide parameters, including a system-synchronizing background cycle. Each Network Processing Unit is provided with sets of special function timers, binary sensors and binary command switches which permit timing of the phases applicable to each intersection and which gate the splits in coordination with the background cycle. Selected phases are serviced in preference to other phases if adequate excess time is available prior to required synchronous operation according to demand within minimum and maximum split limits. In addition, the concept of a fixed phase is introduced, which permits the synchronization of all system operations to activation of a specific phase at a fixed time in a background cycle.