The New Hampshire Highway System is the public roads system of the U.S. state of New Hampshire containing approximately maintained by the New Hampshire Department of Transportation (NHDOT). All public roads in the state are called "highways", thus there is no technical distinction between a "road" or a "highway" in New Hampshire. Overview The state maintains of roads, of which are numbered routes and are unnumbered roadways making up the state's secondary roadway system. The state has of primary highways, which it defines as highways that "connect population centers, other NHS routes within the state, and other NHS routes in the surrounding states: Vermont, Maine and Massachusetts." The remaining of roads are maintained typically by the towns and cities traversed by these roads. Highways assigned a number by the NHDOT are officially known as "New Hampshire Route X", often abbreviated "NH Route X" or simply "NH X". Many minor state highways are not assigned numbers, only local names. The longest highway in New Hampshire is its segment of US 3, which runs for in the Granite State. The longest state highway is NH 16, which runs for . The shortest highway in New Hampshire is NH 10A, which runs for . Interstate Highways A total of of roadway in New Hampshire are part of the Interstate Highway System. Three primary Interstates pass through New Hampshire: I-89, I-93, and I-95. Two secondary Interstates are located in New Hampshire, I-293 and I-393. U.S. Numbered Highways A total of of roadway in New Hampshire are designated as United States Numbered Highways. Four primary routes pass through New Hampshire: US 1, US 2, US 3 and US 4. Two spur routes pass through New Hampshire, US 202 and US 302. Three special routes are designated in New Hampshire: US 1 Bypass, a bypass of US 1 in Portsmouth and Kittery, Maine. US 3 Business, a poorly signed business route of US 3 in Laconia which is concurrent with parts of NH 11A and NH 107. US 302 Business, an unsigned loop of US 302 and NH 16 in Bartlett that is completely concurrent with NH 16A. Turnpike system The NHDOT Bureau of Turnpikes is responsible for maintenance of the public toll roads in New Hampshire: The Frederick E. Everett Turnpike (also known as the Central Turnpike) runs from the Massachusetts state line in Nashua north to Concord. It is cosigned with US 3 in