The Real Reason Behind Why Stop Signs are Red and Octagonal

Thanks to the valuable contribution of William Phelps Eno, the evolution of the modern stop sign occurred, and with it a host of traffic and safety regulations that still benefit society even today.
Mario L. Major

There are some objects of material culture or the world around us which we simply take for granted. They’ve become so deeply ingrained that it becomes difficult to imagine a time when they did not exist. This is even more true in cities, where the urban landscape seems to be changing at an unfathomable pace. How many of us see a bridge added or a building demolished, and after 2 days, 2 months, or even 2 years, cannot clearly remember what was there before?

One example of this is the iconic stop sign. In bright red with its classic—or has it become classic?—octagonal shape, it is an internationally-recognized symbol but what are its origins? A look at the history reveals that both the shape and the color were not a part of the original design. It was part of a longer story that began many years before with one concerned citizen who wanted to see traffic reform.

William Phelps Eno, the pioneer who is given credit for coming up with the original concept of the stop sign and advocating for its widespread use in the early years of the automobile.

As the turn of the twentieth century was a kind of ‘brave new world’ in terms of vehicles, little attention had been paid to how cars would share the space with pedestrians, or with horses or bicycles. “Not only were the streets in those days completely disgusting and filthy, but there were horses and bicycles, and it was just completely chaotic,” said Eno at the time.

The Real Reason Behind Why Stop Signs are Red and Octagonal
Source: The Eno Center for Transportation

Though Eno no doubt used his clout in society as the son of an affluent New England family, he was motivated by a strong civic duty to create the notion of individual responsibility in the mind of drivers. “That was a new concept and really did introduce the idea that you had to watch out for other people,”  Joshua Schank, CEO of the Washington, DC-based Eno Center for Transportation, says about Eno’s idea, adding:

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“The theory is that people will pay more attention to pedestrians and other vehicles and slow down in pedestrian areas if there are no signs, because they won’t know what to do,” Schank says. “That wouldn’t be possible if [Eno] hadn’t first introduced the stop sign.”

He focused on New York City, even at that time an unruly metropolis, assisting the city over the next few decades with developing, first its “rules of the road” in 1909, and in the following decade a manual of police traffic regulations, the first of its kind to ever exist.

The shape and the color 

Thanks to the momentum that was building from Eno’s efforts, different states began to follow suit with small signs and signals. The shape began to evolve in 1923 as part of a scheme from engineers from the Mississippi Valley Association of State Highway Departments that ranked the shapes by degree of caution, from circle for rail crossings, to rectangles and squares. The octagon, in their view, was just under the circle.


The color would come much later after many sign-letter combination trials, with the modern stop sign as we know it today not being unveiled until 1954, ironically after the death of Eno.

“Red has always been associated with stop,” Texas A&M University Professor of Civil Engineering Gene Hawkins says, adding about the issues with the color: “The problem was they could not produce a reflective material in red that would last. It just was not durable until companies came up with a product in the late ’40s, early ’50s.”

Eno, who is now given the title “the Father of Traffic Safety”, never drove once during his life, yet he was determined to make a difference.

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