Everyone who can drive has encountered a stoplight. But what and who decided that red, green, and yellow should be the colors.
Back in the 1830s stoplights first started being used by railroad companies who created the light system to let train engineers know when to stop or go. The different light colors would represent different actions. Red meant stop, green meant caution, and clear (or white) meant go. Making red the color for stop was because it was the color of blood and has been associated with “danger” for thousands of years.
The in 1914 there was an awful train accident that was caused by the red lenses falling out of the red light making it look “clear” which was go at the time. As a result of the accident, it was decided to change the “go” light to green and add a yellow light for caution.
Once the automobile was invented and went into mass production, the obvious move was to adopt the same light system for roads to control the flow of traffic.
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