Ever Wonder?

How highways get numbered? It's rather interesting.

• Interstates always get a one or two digit number and begin with the letter I
• North/South routes are always odd numbered, and East/West routes are even numbered
• If a route connects two interstates, or it's a loop (or beltway), then it's a three digit number based on the interstate number, like how I94 splits into 494, 694 and 394
• There are two different ways to do exit numbering. Both start in the south and west part of the route. In one situation, it's based on mile markers. So if you're 12.5 miles away from the southwest part of the route, you're on exit #12. The other way is based on consecutive numbering. In either case, when you need to add new exits between existing ones, you consecutively letter them (exit #12A #12B, etc)

Pretty neat eh? Information found here and here.