Many minor state highways are not assigned numbers, only local names.

A total of 224.2 miles (360.8 km) of roadway in New Hampshire are part of the Interstate Highway System.

A total of 585.1 miles (941.6 km) of roadway in New Hampshire are designated as United States Numbered Highways.

The NHDOT Bureau of Turnpikes is responsible for maintenance of the public toll roads in New Hampshire: 782 miles (1,259 km) of state-maintained roads are a part of the National Highway System (NHS).

State highways in New Hampshire are marked using square route shields depicting the Old Man of the Mountain.

For multiple alternates of the same route, the state generally uses sequential letters.

US 2 is the only primary US highway within New Hampshire with any spur routes in the state, of which two are present: US 202 and US 302.

Both contain the name of the turnpike over a colored circle, within a rectangular shield with an arced bottom edge.

[2] New Hampshire is one of the few states that still uses sequential exit numbering on its freeways, including all Interstate highways, the Turnpike routes, as well as the NH 101 freeway between Manchester and Hampton.