Abstract: A traffic light control system which includes two-way communications between a moving emergency vehicle approaching a busy intersection with one or more traffic lights, arranged so that the traffic light control apparatus has stored therein preset patterns of response that temporarily preempt the usual operation of the traffic light and instead provides the most effective method of routing the vehicle through the intersection while redirecting general traffic. As part of the invention, the traffic light control mechanism returns acknowledgement of receipt of instructions to the emergency vehicle. The stored preset traffic patterns may in one embodiment be responsive to human intervention from a dispatching center or to time-of-day conditions. The stored traffic patterns in still another embodiment may be arranged to include a plurality of coordinated intersections.

Abstract: Traffic signals at an intersection are controlled by one or more controllers of the state/interval type, located in the vicinity of the intersection. One or more remote units that are portable or mobile communicate with the controller via a coded signal to command specific light operations, instruct a secondary controller to take-over light control at the intersection from a primary controller, and to reprogram the operation of the controller on a temporary or permanent basis. The remote units generate a code that must be received accurately by the controller before commands are followed. In order to economically provide such a code, the code generator employs a diode matrix that orders data words and address words and is easily reprogrammed. The traffic signal indicator operation is monitored by the controller both to detect controller error, as by a voltage error resulting from an incorrect controller action, and to detect a non-controller error, as by a current error resulting from a burned out indicator.