Stoplights Have Long Evolution

Feb. 18, 2005 -- -- It may be one of the most pervasive gadgets in the country, but few know who they can credit (or blame) as they wait for the light to turn green.

The stoplight has a surprisingly erratic history and has evolved into forms so complex that some engineers describe it as a "hanging PC" Most signals today can detect traffic flow through sensors under the roads and then adjust their timing accordingly. And many can automatically change to green at the flash of a strobe light from an oncoming fire truck.

Cutting-edge and future models can even double as surveillance instruments.

"Some of the new models have all kinds of technology now," said Howard Lamunion of Optisoft, a traffic-light company based in Richardson, Texas. "They have video cards, acoustic sensors and network connections."

Of course, early versions of the stoplight, which appeared not long after cars first hit the road, were much simpler creations.

One of the earliest-known models was a revolving lantern with red and green glass that was installed at an intersection in London in 1868. A police officer operated the unit by turning a lever at its base. The idea was novel, but less than a year after its debut, the kerosene-fueled unit exploded and injured the officer who was operating it.

For Garrett Morgan, a black American born of former slaves, the idea sprung from tragedy. While driving around the streets of Cleveland, Morgan witnessed a horrible traffic accident when a car collided with a horse and carriage. The driver of the automobile was knocked unconscious and the horse had to be put down.

Morgan, a successful businessman who had already invented the first version of the gas mask, set to work on a signal that could offer some order on Cleveland's increasingly chaotic and dangerous roads. His hand-cranked invention, patented in 1923, was a T-shaped unit that featured three positions: Stop, Go and an all-directional stop position.