Why Stop Signs Are Red: A Fascinating Origin Story

Do you remember how the first stop sign was put up in Detroit, MI in 1915? It was a 2’x2’ white square sign with black lettering. Since signs were mostly printed in black and white, the MUTCD standardized their meanings via their shape—save for the yellow stop signs, which had already been produced in red but were standardized to yellow in 1920 when people realized that red looks black at night and yellow increased the sign’s nighttime visibility. When did that change?

As you can see, red was already associated with stop signs, but where did this association come from? This information was surprisingly difficult to find, as most articles I found gave vague and general reasons—some of which do make sense. For example, red was already being used for stop signs around the world or to indicate warnings and caution. Red draws the eye, so it’s often been used in signage to get attention, even before the invention of motor vehicles, which brings us to the vehicle we used before what would turn into the modern-day car: the locomotive.

Railways were the first to implement messaging that needed to be visible at a distance, which resulted in the invention of train lights. The first was in 1830, which was made by making a metal sheet box around a glowing light in New York. This light was mass-produced in 1838 and then commonly seen throughout the United States in 1850. These lights were clear and used as a headlight in front of the train to make sure that there weren’t any obstacles on the track. Later, these were used to signal to oncoming trains different messages. White meant that there was another train present that wouldn’t be visible on the timetable, green meant that a scheduled train was closely followed by another, and red lights were to signal the end of a train.

To indicate to others that an oncoming train was approaching, the cross-buck sign was put up where roads and railroads crossed, along with the implementation of a flashing red light: the first of which was in New Jersey in 1913. This is arguably the first use of a red light to tell traffic to stop. One year later, Cleveland, Ohio, put up the first electric traffic signal on August 5, 1914: red for “stop,” green meant to slow down, and white meant “go”—as had been used on the railways.

The choice to use red for stop was not only because of its universal association with caution and danger but (or maybe, this is why) also because it is the color that is best recognized at the farthest distance. This is because of wavelengths and light, and if you want to read more about that process, I’ll include links below because I really do think it’s fascinating. (Plus, it’ll give additional insight into the whole “blue dress/gold dress” ordeal.) Since green is opposite to red (on the color spectrum), it made sense for it to be chosen as the next indicator, leaving white as the third “color”(if you think white is a color)—this color trio gives the most contrast between the three colors. However, white is often seen in nature on its own—sunlight reflecting off of metal or the average person with a lamp would have been in white—which led to confusion for train conductors.

The final straw for “white means go” was after an incident in 1914, where a red lens fell out of the light fixture, signaling a glowing white light. A train collided into another going in the opposite direction and the color change was made. To prevent any future misinterpretation of white light, green became the color to symbolize “go,” and yellow was added to mean caution. Now we know why, for our traffic lights, we have the red, yellow, and green color associations, but when did this information translate over to signage?

If you’re still with me on this post, then you’ll remember back at the beginning when we talked about stop signs being both yellow and red throughout the country. Since red looked black in the nighttime, red stop signs didn’t grab attention as needed — instead, red stop signs looked just like the other black and white standard signage being made during the time.

This all changed when retroreflectivity came into play for road signage—a wildly interesting topic that you can learn more about via our video or even a previous blog post —finally, a sign’s visibility wouldn’t be affected by its color and instead could be read by reflecting headlights.

Now that we have the history of where these colors come from for our everyday signage, we’re going to focus on the use of green, blue, and brown next time!

For the scientific breakdown of how red, yellow, and green are processed by the eye, check out these great sources below:

https://www.thoughtco.com/understand-the-visible-spectrum-608329https://www.thoughtco.com/the-visible-light-spectrum-2699036

https://science.nasa.gov/ems/09_visiblelighthttps://www.britannica.com/science/color/The-visible-spectrum