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Nugget of Knowledge: Traffic light colors


Traffic lights come from our railroad system of the 1800s

(WYTV) – Red says stop, and green means go.

How did these colors become our traffic signals?

Someone had to create this system.

Traffic lights come from our railroad system of the 1800s. Train engineers needed to know when to stop their locomotives and when to slow down.

Red was an easy choice for stop.

Red already means something potentially serious or dangerous, and red has the longest wavelength on the color spectrum. Train engineers could see it from a longer distance, a distance they needed to stop.

They also chose white to mean go and green to mean caution, and we’re not sure why. Maybe because of the way they contrasted with red.

If a lens fell off a red light or green light, you had a white go light. Stars would be mistaken for a white light, too.

So engineers added yellow to show caution, and green was shifted to the go signal.

Not everyone used the same colors, so the the Federal Highway Administration mandated the red, yellow and green color scheme in 1935.

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