General Question

Bluefreedom's avatar

How did we come to use the colors red, yellow, and green for traffic signal devices at intersections?

Asked by Bluefreedom (22926points) October 30th, 2008

I was going to research this on the Internet but I’d rather reap the knowledge of esteemed Flutherites who are in the know on this information.

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3 Answers

AlfredaPrufrock's avatar

The world’s first three-color, four-direction, elec. traffic lamp, was installed at the intersection of Woodward Ave. and Fort Street, Detroit, Michigan in October, 1920. It was designed by Superintendent (then inspector) William L. Potts of the Signal Bureau, Detroit Police Department. Basic design remains practically unchanged today. The signal remained in use until 1924 and became a part of the world’s first synchronized signal system. This system extended from Jefferson to Adams on Woodward Avenue and was controlled manually from a tower at Woodward and Michigan.

museum archives, Henry Ford Museum & Greenfield Village (as of Jan 29 2003)

The meanings of the colored lights were essentially the same as today. Green meant “go”; red meant “stop”; and yellow (amber) meant “clear the intersection” (Mueller 1970). An analogous color scheme had been used by the railroads, where as early as 1899, the New York, New Haven and Hartford Railroad introduced a system wherein red, yellow, and green meant “stop”, “caution”, and “all clear” respectively (Brignano 1981).

loser's avatar

Hmm! I always thought some rasta dude came up with it!

La_chica_gomela's avatar

What a great question, blue! You’ve got me curious now!
So when and why did they start using it at railroads then?

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