Who invented the traffic signal?

Garrett Morgan See website: http://inventors.about.com/library/inventors/blgas_mask.htm ---- The world's first traffic light was operating in London, England, even before cars were invented. It was a revolving gas-lit lantern with red and green signals, but in 1869, the light exploded, injuring the policeman who was operating it. In the early 1900s Garrett Morgan, an African-American living in Cleveland, Ohio, developed the electric automatic traffic light, originally based on a semaphore-system. Shortly after this, Detroit police officer William L Potts developed the first 4-way three colour traffic light using red, amber, and green railroad lights.