BrainStuff Classics: 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 classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio. Hey Brainstuff.
Lauren Vogebomb here with another classic episode from the Vault.
In this one, we take a look at the history
of a common, everyday object so ubiquitous that you probably
don't think much about it, but that was nonetheless designed
to stand out. We're looking at the traffic stop sign.

(00:27):
Hey brain Stuff. I'm Lauren vogelbamb and today's question is
why are 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, there 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

(00:48):
nineteen fifteen. According to historical estimates by the Federal Highway Administration,
in nineteen fifteen, there were already almost two point five
million cars driving on US roads when 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 that we know and love today,

(01:09):
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 nineteen thirty five, the
United States got its first official manual on Uniform Traffic
Controlled Devices, which said stop signs should be a yellow
octagon with black or red lettering. It wasn't until the

(01:31):
nineteen fifty four revision of this nineteen forty eight 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
explained that the original decision to use yellow instead of
red was because red pigments were more likely to fade

(01:54):
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
a question that goes deeper than uniform traffic signaling protocol.

(02:16):
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
administration has repeatedly rejected our proposal for a green and

(02:37):
brown camouflage patterned stop sign. Another important point is that,
like the aforementioned manual says a red is a color
we consistently use to identify warnings and peril a 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

(02:59):
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
twenty eleven study published in Psychological Science found that male
recis monkeys under test conditions were less likely to steal
apple slices from human experimenters who were dressed in red.

(03:23):
The monkeys didn't seem to care about the gender of
the human experimenter and were 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 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

(03:46):
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,
hey guys, it might be nice if you've came to
a halt or you know, turned off your nitro boosters.

(04:10):
Today's episode is based on a video script written by
Joe McCormick for the brain Stuff YouTube channel, which is
a thing that we used to have to hear more
from Joe check out his podcast Stuff to Blow your Mind.
Brain Stuff is production of iHeartRadio in partnership with houstuffworks
dot com and it is produced by Tyler Klang. Four
more podcasts my Heart Radio, visit the iHeartRadio app, Apple Podcasts,

(04:30):
or wherever you listen to your favorite shows.