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I had no idea about the interstate numbering system. This is awesome to know, thanks.
by amadeusw 7y ago
I had no idea about the interstate numbering system. This is awesome to know, thanks.
- munificent 7y agoIt's a cool system. The numeric rules are (though there are lots of exceptions): * Primary interstates are one or two digits. Shorter spurs, loops, and connectors are three-digits. * East-west primary interstates are even-numbered, north-south are odd. * Major arterials are divisible by five. (The longest interstates are I-90, I-80, I-40, I-10, I-70, I-95, and I-75.) * Odd routes increase in number going from west to east. * Even routes increase in number from south to north. * The last two digits of a three-digit interstate usually identify its main parent interstate. (For example, the I-310 spur connects I-10 to US 90.
- whyaduck 7y agoEven routes increase from south to north (e.g. I-10 runs through Arizona, I-90 runs through Washington).
- munificent 7y agoOops, fixed.
- mynameisvlad 7y agoAnother 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 7y agoI-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.)