David Lawson, age 11, of Falmouth, Me., for his question:
WHEN WAS THE TRAFFIC LIGHT INVENTED?
Once upon a time when the automobile was a baby "horseless carriage," traffic congestion was unheard of. A driver puttered along at a comfortable pace about 15 miles an hour and if he came to an intersection he slowed down, looked both ways and proceeded without incident. Today, with about 100 million cars clogging the roads and highways, traffic signals are essential.
The need for traffic control was felt many years before automatic traffic lights made their debut. Patrolmen perched on a platform in the middle of an intersection were the first traffic controllers. Their hand and arm signals, often accompanied by shrill whistle blasts, gave a "stop" or "go" message to drivers.
Even as far back as the early 1900s busy cities found they needed patrolmen working in 24 hour shifts, using hand¬operated battery charged signals. But as traffic increased, there simply were not enough patrolmen to cover every busy corner. Small wonder that the invention of the automatic traffic signal was a welcome one.
The first automatic traffic signal was installed Aug. 5, 1914, in Cleveland, Ohio. By today's standards it was a crude affair, strung about 15 feet above the middle of the intersection. The red light and the green light were accompanied by buzzers, which sounded long or short blasts to go with "stop" or "go."
Traffic signals installed on the corners of streets began appearing in the late 1920s and have become more complicated as traffic problems mounted. The first lights gave the same duration of green or red regardless of the time of day, which often caused traffic jams, rather than cured them. In 1928 one of the first lights designed to adjust to traffic conditions was installed in New Haven, Conn. This device operated when a car passed over a detector in the road pavement, signaling the "call box" on the light pole to change.
Charles Adler invented another type of traffic light ¬one which used the sound of the car horn to activate the call box. Other sound activators relied on the normal operating sounds of the car rather than the horn.
Nowadays, most large, metropolitan cities use computerized traffic signal systems. New York City and Toronto, Canada, for example, have gigantic computers which sort information fed through wires from detectors in the road pavement.
Before installing an electric signal, surveys are made to determine many factors such as the number of motor vehicles using the intersection per hour and the amount of pedestrian traffic. The cost of putting in a brand new signal varies, of course, but city managers tell Andy it is usually around $55,000 or more.