Maine has one primary Interstate highway, I-95, within its borders, as well as four related routes: I-195, I-295, I-395, and the unsigned I-495.

US 2 has two alternate alignments designated US 2A as well as two child routes - US 202, a southwestern spur stretching to Delaware, and US 302, a western loop connecting US 1 in Portland to US 2 in Montpelier, Vermont.

[2] State-aid highways are roads chosen by the local municipality which serve as links between other state routes.

Winter snow removal is the responsibility of the municipality, while other maintenance and funding is handled by the state, with the exception of urban compact areas.

Townways in Maine are classified as all highways that do not fall into one of the preceding categories.

These roads are chosen, funded, and maintained by the towns, or the county in unorganized areas.