Signal systems without cables

A method is presented for achieving many of the benefits of linking isolated signalized intersections into systems without incurring the costs of either cable installation or leased communication channels. The method may be considered an interim step where traffic responsive systems are planned or as the final solution in situations where responsive systems are not warranted. The method employs a microprocessor together with an accurate clock whose stability is based on electrical service frequency under normal conditions and on a quartz crystal and battery under power failure conditions. The traffic advantages include all those-attributed to systemization but not those of traffic responsive operation. Other advantages include the initial cost, well below that of cable installation, and an excellent record of reliability and low maintenance costs. Development of similar devices in the U.S. is reviewed briefly with a limited amount of cost comparison against the Australian unit. The equipment described offers a quicker and less costly means for setting up multiprogrammed signal systems either on an interim or permanent basis. The technology is within the current state of the art and should be applicable in many areas, particularly for arterial commuter routes where signal spacing is much greater than in central business district (CBD) situations.