‘Interstate’s Forgotten Code’ Explains Hidden Meaning Behind Numbered Road Signs

Ever wonder why U.S. interstates are numbered the way that they are? One YouTube channel explained it all in a video.

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A YouTube video titled The Interstate's Forgotten Code explained how the interstate system was numbered with odd and even numerals and how they run north and south and also east and west.
Image via Dünzl\ullstein bild via Getty Images

On Feb. 10, 2022, the CGP Grey YouTube channel premiered a new video titled, “The Interstate’s Forgotten Code,” that explained the hidden meaning behind numbered road signs. We previously reported on the same subject back in 2001.

Three days later, a Facebook user named Rich Evans shared a post about the video. It went viral and was shared well over 300,000 times in just five days. The post was likely the main reason the YouTube video was viewed nearly 3 million times in just over one week.

Facebook Post

Evans’ Facebook post provided a brief summary of the eight-minute video, explaining the basics of how the U.S. interstate system was laid out:

The post that promoted the “Interstate’s Forgotten Code” video read as follows:

I always knew there was a logic to it, but I never saw it explained so well until I stumbled upon this delightfully informative short video on how the US interstates are numbered.

Those with 2-digits traverse the entire country
If they end in “0” they run East-West (10, 20, 30, ..)
If they end in “5” they run North-South (5, 15, 25, ..)

Those with 3-digits are bypasses and contain the last 2 digits of the interstates they bypass.

That’s it! (plus exceptions ? )

Neat!

This was all true. Next, we’ll look at another helpful explanation that we found in newspaper archives.

A YouTube video titled The Interstate's Forgotten Code explained how the interstate system was numbered with odd and even numerals and how they run north and south and also east and west.
An example of an interstate and a bypass. (Courtesy: formulanone/Flickr)

‘National Standards’

On March 28, 2005, the Sioux City Journal in Iowa also broke down the U.S. interstate system. The explanation came in the form of an answer to a reader:

Interstate highways are numbered and mile-posted according to consistent national standards, states the Iowa Department of Transportation. Even numbered interstates run east and west while odd numbered interstates run north and south. Interstates with three-digit numbers are spur routes, bypasses, or beltways. Interstates with numbers ending in zero run from coast to coast while those with numbers ending in five run from border to border.

Mileposts run from state line to state line, either from south to north or from west to east. Interchange numbers are assigned based on the nearest milepost. When more than one interchange is located within a mile, letters are assigned to designate the individual interchanges.

The answer was written in journalist Jeannette Lubsen’s “Ask Jeanette” column.

A YouTube video titled The Interstate's Forgotten Code explained how the interstate system was numbered with odd and even numerals and how they run north and south and also east and west.
Route 66 in Flagstaff, Arizona, a meeting point for major roads. (Courtesy: Xomiele/Flickr)

The Video

The video on the CGP Grey YouTube channel contained quite a bit of motion graphics in order to fully explain the interstate’s entire “forgotten code.” It started out by explaining how most interstates that run east and west end with a 0, while those that run north and south end in a 5:

The top comment on the video said: “My Dad’s a truck driver. It amazed me that he could plan a cross-country road trip without even looking at a map. That sneak had a cheat code the whole time!”

A user from Australia also joked of the “Interstate’s Forgotten Code” video: “I’m so lucky to be living in Australia. All I need to remember is that if I dive in any direction long enough I run the risk of dying in the middle of nowhere.”

Sources:

CGP Grey on YouTube. ? ? The Interstate’s Forgotten Code ? ?. 2022, https://www.youtube.com/watch?v=8Fn_30AD7Pk.
 
Evans, Rich. Post on Facebook.com, 13 Feb. 2022, https://www.facebook.com/rkevans6070/posts/10227419006609125.
 
Lubsen, Jeannette. “Ask Jeannette.” Sioux City Journal on Newspapers.Com, 28 Mar. 2005, http://www.newspapers.com/image/336316354/.