Why Are Stop Signs Red?

Stop signs were always the red octagons we know today -- so how was the color chosen, and why has it stuck? Learn about the history and psychology of red traffic signals in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
I'm Lauren Vogelbaum, and today's question is why our stop
signs read? 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.

(00:23):
Believe it or not, the first stop signs in America
were not put in place until nineteen fifteen. According to
historical estimates by the Federal Highway Administration. In nineteen fifteen,
they were already almost two point five million cars driving
on US roads when those much needed first stop signs
finally did show up. It happened in the motor capital

(00:44):
of Detroit, Michigan, and they were not the red octagons
that we know and love today, but white squares with
black letters. Now. Traffic sign codes throughout the twentieth century
have recommended several different variations on the basic design. For example,
in ninety five, United States got its first official manual
on Uniform Traffic Controlled Devices, which said stop signs should

(01:06):
be a yellow octagon with black or red lettering. It
wasn't until the nineteen fifty four revision of this edition
of the manual 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

(01:27):
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
nineteen fifties, 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

(01:51):
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 eighty
eight 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

(02:13):
Administration has repeatedly rejected our proposal for a green and
brown camouflage pattern to stop sign. Another important point is that,
like the aforementioned Manuel says, a 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

(02:35):
colors with specific messages. So even if you only catch
the hint of a red sign out of 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
study published in Psychological Science found that male reesist monkeys

(02:55):
under test conditions were less likely to steal apple slices
from human experience mentors who were dressed in red. The
monkeys didn't seem to care about the gender of the
human experimenter, and we're not deterred by green or blue clothing,
but a red hat and T shirt were enough to
make the monkeys cautious about swiping that fruit. Now, it's
important not to read too much into that result. The

(03:16):
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 hypothetical primate instinct, the difference between a red stop
sign and a yellow stop sign might be the difference
between stop and the name of the law. And hey, hey,

(03:38):
hey guys, it might be nice if you came to
a halter you know, turned off your nitro boosters. Today's
episode was written by Joe McCormick and produced by Tyler Clang.
For more on this and other arresting topics, visit our
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