How are Insterstate Highways Numbered?

[Kelemvor]

I never knew what the exact plan was on how various types of highways are numbered but I was browsing through Snopse and came across this.

Really good reading.

http://www.snopes.com/autos/law/highways.asp

Snippet:

INTERSTATE HIGHWAYS: Under the plan developed for a national interstate highway system during the Eisenhower administration, interstate highways (marked with the familiar red-and-blue shields) are numbered according to the following rules:

* Major 5!interstate highways are identified by one- or two-digit numbers. North-south routes are assigned odd numbers, with the numbers growing larger from west to east; east-west routes are assigned even numbers, with the numbers growing larger from south to north.

 

[BrokenVisage]

I already knew this from reading my drivers permit packet a while ago.

 

[IronWing]

Urban spurs carry an odd numbered prefix while urban bypasses carry an even numbered prefix.

 

[Atomicus]

Odd numbers run North to South, with east to west numbers decreasing in value.
Even numbers run West to East, with the highest numbers starting from the north I think.

There was an episode about the US Highways last night on the History Channel. :thumbsup:

 

[Zenmervolt]

Originally posted by: ironwing
Urban spurs carry an odd numbered prefix while urban bypasses carry an even numbered prefix.

Also, spurs and by-passes are always 3-digits. If the interstate they branch from is only one digit, a 0 is placed in the middle of the spur or loop's name. (E.g. I-405 is a loop around Seattle off of I-5, I-705 is a spur off of I-5 in Tacoma.)

ZV