Traffic signals have been around since 1868, but on November 20th, 1923, African-American inventor Garrett A. Morgan got a patent for his hand-cranked traffic signal using a T-shaped, three-position system.
In addition to having "stop" and "go" indicators, it had an "all stop" signal that could be used to clear the intersection to allow pedestrians to cross or to stop cross-traffic before signalling a different direction to proceed.
At night, when traffic was light, it could be set at half-mast (like a blinking yellow light today), warning drivers to proceed carefully through the intersection.
Morgan eventually sold the rights to his invention to General Electric for $40,000.
Sources: Wikipedia, History.com, Enchanted Learning
In addition to having "stop" and "go" indicators, it had an "all stop" signal that could be used to clear the intersection to allow pedestrians to cross or to stop cross-traffic before signalling a different direction to proceed.
At night, when traffic was light, it could be set at half-mast (like a blinking yellow light today), warning drivers to proceed carefully through the intersection.
Morgan eventually sold the rights to his invention to General Electric for $40,000.
Sources: Wikipedia, History.com, Enchanted Learning