US Highway Numbering System

[thriftylefty]

I am not sure if this is a consistent rule , but in the case of I-35 if the number preceding it is odd means that route will take you through the metropolitan area and if the number is even it will take you around the metropolitan area as in 135, 635, 435 and 35 in KC , or 110, 710,210 and 10 in LA

[lothartheterrible]

Originally Posted by thriftylefty

I am not sure if this is a consistent rule , but in the case of I-35 if the number preceding it is odd means that route will take you through the metropolitan area and if the number is even it will take you around the metropolitan area as in 135, 635, 435 and 35 in KC , or 110, 710,210 and 10 in LA

That is correct; three digit Interstate numbers beginning with an odd number spur into a city and those beginning with an even loop around it. Funny thing is, if you look at a map, you will see that several of these three digit numbers are used more than once. For example, there is an Interstate 635 looping around both Kansas City and Dallas, an Interstate 220 encircling both Shreveport, LA and Jackson, MS, and there is an Interstate 110 spurring into both Los Angeles and El Paso.

[mwruckman]

Originally Posted by gdude

Most of what would become Interstate 90 from Illinois to New York was constructed before the Interstate Highway Act was passed in 1956.

Most of I-90 east of Chicago was originally built as state turnpikes such as the New York State Thruway (Albany to Buffalo, the Ohio Turnpike and the Indiana Toll Road. They joined the Penna Turnpike (I-76, I476), The Mass Pike (I-90)and The New Jersey Turnpike (I-95 and I-295).

[Jill61]

In St. Louis I270 makes a loop around the city, crossing several major interstates; 44, 55, 64 & 70. Way back in the day, someone got the insane idea to number it thusly:

Northbound between 55 and 44, heading towards 44, it was 244 (to 44, get it?)

After crossing 44, still heading Northbound, you would now be traveling on highway 264, until such time as you crossed I64, at which point

Now you'd be on highway 270, since you're heading to highway 70.

On the opposite side of 244, those heading Southbound going towards I55 would be traveling on highway 255.

Southbound travelers between I70 & I64 would be on highway 264 (remember, their Northbound counterparts were traveling on highway 270 at this same point).

To the genius who came up with this. . .



There is still a remnant of this old numbering system southeast of I55, where I270 is still known as I255.