Staggered Traffic Signals

(in Russian, zelenaia volna, “green wave”), an automatic control system for traffic signals that ensures the safe movement of vehicles over major city streets. The signals are set for a given average speed; a series of traffic lights is interconnected so that the signal lights turn green at the moment when compact groups of vehicles reach them.

The introduction of a coordinated control system of this type has a number of advantages compared with individual control for each intersection: it increases the speed of the traffic on major streets, decreases the time that vehicles must stop at intersections, and reduces the number of traffic accidents. The same cycle, usually 45–80 sec, is set at all the intersections coordinated according to the principle of staggered signals. The signals turn green in a predetermined sequence depending on the direction of traffic flow, rather than at all intersections along the street at the same time. Therefore, the system may be used with any distance between intersections. In addition to traffic lights, special indicators that show the rated speed and the speed required at a given moment are used to increase the operating reliability of the system. Systems of staggered traffic signals are in use in a number of cities in the USSR (Moscow, Leningrad, Kiev, and Alma-Ata) and in major foreign cities (Paris, Rome, and others).