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Radio Record, Volume III, Issue 9, 13 September 1929, Page 9

Since operation of the signals is operated ; by the actual necessities of the traffic flow, it is expected-that a considerable saving of time will result, especially at night when delays for which there are no necessity occur. The purpose.of this installation, which is the first in the world, is to determine the practicality of the’ invention, Simple instructions for, operating the lights are. given on signs maintained by the Pittsburgh Traffic Planning Department. The signs read, "To get the green light, pull-up to the line.". | HE automatic feature of the system is made possible by a new application of the photo-electrie cell, or "electrie eye," which literally "sees" automobiles and regulates the signals accordingly, it is an automobile’s shadow, falling on an "electric eye" from an over-head lamp, assuring a sufficiently dense shadow, night and.day. ‘Traffic is routed through this beam of light. The new system is designed to set automatically right any unusual situation that might present itself. For instance, if an unusually large number of cars on one street threatens to hold up traffic on the other street inordinately long, the signals operate ou a definite pre-arranged programme, giving each line of traffic a fair share of time. If the automatic control feature should break down for any reason, the signals would. operate on the normal programme,