Interstate Highways: Every Main Route Compared

What counts as a main Interstate

Interstates with one or two digits are the trunk routes. Odd numbers run north and south, rising from the west coast to the east, and even numbers run east and west, rising from south to north. Three-digit routes such as I-295 or I-635 are spurs and loops off a parent route, and they are covered on each parent's guide rather than in this table. Hawaii's H-routes and the unsigned Interstates in Alaska and Puerto Rico are left out. A few numbers belong to two separate roads, including I-74, I-76, I-84, I-86, I-87 and I-88, so their state lists cover both.

Reading the table

Mileage is what the Federal Highway Administration's Route Log books to each route number. Where two Interstates share pavement, the Route Log credits the shared miles to one of them, so a figure here can sit below the end-to-end length a motorist would log. That is why the Route Log books more miles to I-80 than to I-90, even though I-90 is the longer road from end to end: I-90 shares pavement with I-94 in Wisconsin and Illinois and with I-80 on the Indiana and Ohio turnpikes, and the Route Log books those miles to the other routes. The crash columns count deaths on each route's mainline in NHTSA's fatality file, and the rate divides deaths per year by route miles so long rural routes and short urban ones can be compared. Routes under 100 miles get no rate, because a handful of crashes swings it too far. For how highways are sorted into classes beyond the Interstate tier, see highway functional classification explained.