Interstates U.S Highways

[doglover44]

Always wondered what the difference between the 2.

[corco]

That's three words (four if you want to get technical), all with dramatically different definitions

[jp the roadgeek]

I can sum it up in two words: traffic lights.  One has them; the other, unless you live in a certain town in Pennsylvania, does not.

[US 89]

I can sum it up in two words: traffic lights.  One has them; the other, unless you live in a certain town in Pennsylvania, does not.

Or a certain interstate in Wyoming.

[bulldog1979]

For a quick primer, see:

https://en.wikipedia.org/wiki/United_States_Numbered_Highway_System
https://en.wikipedia.org/wiki/Interstate_Highway_System

Both are national systems that cross state lines and use a consistent marker across state lines. Both use a grid system with odd-numbered highways that run north—south and even-numbered highways that run east—west. The lowest U.S. Highway numbers are in the north and east, increasing southward and westward; the Interstate Highway grid is the opposite.

U.S. Highways don't have a minimum design standard, so they vary from two-lane highways to multi-lane freeways. Interstate Highways, with some exceptions, are freeways with minimum standards for design. The US Highway System is also 30 years older than the Interstate Highway System.

The other key difference is the location of the systems. The US Highway System only exists in the 48 contiguous states and DC. There are Interstates in all 50 states plus DC and Puerto Rico. The Interstates in Alaska and Puerto Rico are not signed, nor are they required to meet the same design standards as in the other states. Hawaii's Interstates are freeways and signed.

[Hurricane Rex]

I can sum it up in two words: traffic lights.  One has them; the other, unless you live in a certain town in Pennsylvania, does not.

Or a certain interstate in Wyoming.

Does the Interstate bridge count as a traffic light?

[hbelkins]

Also, the sanctioning process. U.S. highway numbers are approved by AASHTO, which is a voluntary organization which has no binding jurisdiction. While AASHTO has been given a voice in determining Interstate highway numbers, the final decision resides with FHWA, which is a government agency and has binding jurisdiction. Unless, of course, Congress legislates that a certain route will be given a certain number.