Haven't been here for a while. I'll give some explanation in a minute. First, though...

See the link below:

I've known this for years. I've hitchhiked most of these routes, personally. In fact, I-80, "The Mainstreet of the Midwest," has been my own main-street most of my adult life.

The funny part of this is when you get to then spurs:

When the first digit is an odd number it is a spur and does not reconnect.

When that first number is even, they reconnect, (somehow.)

Here in the bay area we have an abundance of '80's routes. I- 80, I-280, I-580, I- 680, I-780, and I-880, In fact, I think we must have used up damn near all the '80's offshoots for the whole country.

That's why, (and here's the funny part,) in Hayward area they have to take a local highway, highway 238, and turn it into Interstate for about a mile between I-580 and I-880. It is not a spur of either '80 highway.

Also, why does I-880 get credit for reconnecting with I-80, (probably through I-280, which also has an even first digit,) yet I-580 doesn't even though it connects to I-880 through I-238, and again to I-80 directly, up near the bay bridge.

http://whoknew.news.yahoo.com/?nc&vid=25223790