Who invented the first traffic light?

Police Officer William L. Potts of Detroit, Michigan, decided to do something about the problem caused by the ever increasing number of automobiles on the streets. What he had in mind was figuring out a way to adapt railroad signals for street use. Potts used red, amber, and green railroad lights and about thirty-seven dollars worth of wire and electrical controls to make the world's first 4-way three color traffic light. It was installed in 1920 on the corner of Woodward and Michigan Avenues in Detroit. Within a year, Detroit had installed a total of fifteen of the new automatic lights.

---- The world's first traffic light was operating in London, England, even before the first car was invented. Installed at a London intersection in 1868, it was a revolving gas-lit lantern with red and green signals. However, on 2 January 1869, the light exploded, injuring the policeman who was operating it. Obviously, a safer, more reliable system was required. In the early 1900s, Garrett Morgan of Cleveland, Ohio, developed the electric automatic traffic light. Originally based on a semaphore-system, it was William Potts (see above information) who developed the traffic lights become the red-amber-green lights they are today.