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Why Are Stop Signs Red?


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Channel: BrainStuff - HowStuffWorks
Categories: Society / Culture   |   Psychology   |   Science   |   Social Science  
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Why aren’t stop signs yellow, purple or green? Brainstuff explains the origins of the red, octagonal stop sign and some hints about why red might be the best color to use if you want to throw cold water on somebody’s need for speed.

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OK, no messing around, because I know you’re in a hurry. Today’s Brainstuff question is: “Why are stop signs red?” Why not green or purple? Why not mango tango or tickle me pink?

In the early days of motor vehicles, the rules of the road were… let’s say they were really more what you’d call “guidelines” than actual rules.

Believe it or not, the first stop signs in America were not put in place until _915.

When those much-needed first stop signs finally did show up, it happened in the motor capital of Detroit, Michigan, and they were not the red octagons we know and love today, but white squares with black letters.

Now, traffic sign codes throughout the 20th century have recommended several different variations on the basic design.

For example, in 1935, the United States got its first official Manual on Uniform Traffic Control Devices (or MUTCD), which said stop signs should be a yellow octagon with black or red lettering. It wasn’t until the 1954 revision of the 1948 edition of the MUTCD that the red octagon with white letters became the law of the land.

According to that document, “The red color is consistent with the accepted use of a red light as a Stop signal and of the color red as a special warning of danger.”

Furthermore, they explained that the original decision to use yellow instead of red was because red pigments were more likely to fade over time with exposure to the elements.

However, by the 1950s, the state of California had solved the problem by using porcelain enamel to protect their precious red signs, and higher-durability red paints were becoming more widely available. And like that, red became the new yellow.

But there’s a question that goes deeper than uniform traffic signaling protocol: Why red? Is there any reason to think a red stop sign would work better than any other color at getting drivers to stop zooming straight through intersections at 88 miles per hour?

One fairly obvious answer is that red is not as likely to blend in with the landscape as some other colors. This explains why the Highway Administration has repeatedly rejected my proposal for a green-and-brown, camouflage-patterned stop sign.

Another important point is that, like the MUTCD says, red is a color we consistently use to identify warnings and peril. Think about the “Wrong Way” sign and the “Do Not Enter” sign.

Having consistent color-coding helps drivers learn to identify specific colors with specific messages, so even if you only catch the hint of a red sign out the corner of your eye, you’re more likely to react with caution, the way you’ve been taught.

There are also some behavioral research findings that might point to the inherent power of the color red to command our obedience. For example, a 2011 study published in Psychological Science found that male rhesus macaque monkeys under test conditions were less likely to try to steal apple slices from human experimenters dressed in red.

Now it’s important not to read too much into these results: The study was done on monkeys, who could be reacting to red for all kinds of reasons. But it at least suggests the possibility that there is a primate instinct to associate red with dominance or authority.

And if humans share this primate instinct, the difference between a red stop sign and a yellow stop sign might be the difference between, “STOP IN THE NAME OF THE LAW” and “Hey, hey, hey guys – it might be nice if you came to a halt, or, you know, at least turned off your nitro-boosters…”


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  • John Added amazing video, very informative, thanks!!