[mynameisvlad]

Another fun tidbit is that any 3-digit interstate is an auxiliary route of the 2/1-digit mainline. The first digit determines the type of route, with odd being a spur and even being a bypass or beltway. So I-405 is a bypass of I-5, and I-110 is a spur off I-10 connecting it to the Port of LA.

[wahern]

I-110 is also a spur connecting I-10 to downtown Pensacola, FL, Biloxi, MS, and downtown Baton Rouge, LA.

And apparently there's a I-405 in Seattle. (All the I-110 spurs I've driven on.)