Controlling Traffic

Radio Record, Volume III, Issue 25, 3 January 1930, Page 7

Controlling Traffic

_ Pittsburg System. "TRAFFIC. eyes,". which ‘automatically control traffic lights when they "see" motor-cars, are in. service in Pittsburg, U.S.A. The purpose of the new system is to eliminate unnecessary traffic delays by giving the right of way continuously_to traffic on a main street, interrupt« ing the main traffic flow only when cars are actually waiting on the side street to cross the intersection. Motorists on one street are given a green or "go" signal continuously until a car on the cross street comes Within a sort distance of the intersection, at which time the traffic signal mechanism starts to operate and the lights go through one complete cycle, allow traffic on the one street to pass through, and then stop again with the green light on the other street. The lights then allow traffic to proceed uninterruptedly on the one street until the presence of cars on the other street justifies another change. Since operation of the signals is regulated entirely by the actual necessities of the truflic law, it is expected that a considerable saving of time will result, especially at night, when delays for which there, is no necessity occur, . , The . purpose of the installation, Which is the first in the world, is to determine the practicability of the invention of Dr. Phillips Thomas, research engineer of the Westinghouse Wlectric and Manufacturing Company. ‘Simple instructions for operating the lights are given. on signs maintained by the Pittsburg Traffic. Planning Department. The signs read: "To get the green light, pull up to the line." The automatic feature of the system is made possible by a new application of the photo-electric cell, or "electric eye,’ which literally "sees" motor-cars and regulates the signals accordingly. It is the motor-car’s shadow, falling on an "electric eye" from an overhead lamp, that assures a sufficiently dense shadow, night and day. Traffic is regulated through this beam of light. ae The new system is designed to set. automatically right any unusual situ‘ation that might present itself. For instance, if an unusually large number of cars in one street threatens to hold up traffic in the other street inordinately long, the signals operate on a definite pre-arranged programme, giving each line of traffic a fair share of time. *