A waste of $100,000,000 is charged up to traffic tie-ups and inconvenience in the United States every year according to Dr. Miller McClintock, director of the Albert Russel Erskine Bureau for Street Traffic Research which is financed by the Studebaker motor car company. Much of this loss is due to traffic stop signals which have been constructed either on an unsound engineering basis or without the justification of acute traffic conditions. Moving vans and commercial vehicles whose runs cost five cents a minute, and more, as well as pleasure vehicles are being blocked in some localities by signals that are 100 per cent inefficient.
Massachusetts, however, through its Department of Public Works requires that certain standards be complied with before a town be permitted to install traffic lights. There must be a minimum total of 500 vehicles an hour at an intersection where 25 per cent of the traffic is cross traffic. If the number of cars per hour falls below the standard for a period of 120 minutes, the signal must be turned off. These requirements were suggested by the Erskine Bureau which had made a complete study of motor travel in the state.
Dr. McClintock, who laid out the traffic signal plans for Chicago, Kansas City, Boston, San Francisco, and Los Angeles, revealed that in many cases small towns or store districts desired lights merely for the purpose of adding prestige to their localities. In one extreme instance 45 sets of signals were equally distributed among the aldermen of a certain town to be handed out for political gain. Education of the public, however, is quickly doing away with such conditions.
Signal systems may be divided into two categories: independent and coordinated. The independent lights change at fixed intervals or may be changed by electrical contact caused by a car approaching the intersection. Coordinated lights are controlled in relation to other lights and may be simultaneous or progressive. Simultaneous lights are used in New York, but are technically unsound because they result in a high moving speed and a slow overall rate. The progressive lights as they are used on Washington Street in Boston are theoretically ideal and permit a quick and continuous flow of traffic.