[meyer]

I-270 circles Columbus, Ohio. How can there be two I-270s?

[Paladin2]

It’s the way the Interstates were set up to number local beltways and spurs. Eisenhower’s Fault...

[Paladin2]

I think it was originally labeled I-70S...

[FredZarguna]

There is no limitation on the use of auxiliary interstate highway designations (3 digit I-xNN) except within state. There cannot be multiple I-270’s in OH, but there can be I-270’s in any other state along I-70.

[Paladin2]

“Those victories meant during his time as chairman numerous transportation projects were funded, including Interstate 99, the only Interstate highway to have its route number (a violation of the usual Interstate numbering standard) written into law. The route was later named the “Bud Shuster Highway” by Governor Robert Casey. “

[Olog-hai]

There are six I-495s. Only one of them is the Long Island Expressway in New York. Only one of them is the Capital Beltway in Washington DC too. Three-digit “interstates” are interstate connector routes.

[Tolerance Sucks Rocks]

It appears that you can use a three-digit number for one highway in each state. So, in our example, we have an I-270 in Maryland, one in Ohio, one in Colorado, and one straddling Illinois and Missouri.