The New Hampshire Highway System is the public roads system of the U.S. state of New Hampshire containing approximately 17029 mi 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 4814 mi of roads, of which 2567 mi are numbered routes and 1465 mi are unnumbered roadways making up the state's secondary roadway system. The state has 557 mi 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 12215 mi 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.

Interstate Highways

A total of 224.2 mi of roadway in New Hampshire are part of the Interstate Highway System.

U.S. Numbered Highways

A total of 585.1 mi of roadway in New Hampshire are designated as United States Numbered Highways.

Turnpike system

The NHDOT Bureau of Turnpikes is responsible for maintenance of the public toll roads in New Hampshire:

National Highway System

782 mi of state-maintained roads are a part of the National Highway System (NHS). Of the NHS roads in the state, 225 mi are Interstate highways (35 mi of which are also on the New Hampshire Turnpike System); 52 mi are non-interstate turnpike highways; and 505 mi are non-interstate and non-turnpike highways.

Classification of state highways

New Hampshire RSA 229:5, "Classification", sets out the seven different classes of highways in the state: Under RSA 229:5, V, the Commissioner of Transportation may establish compact sections in the following cities and towns:

Routes crossing state lines

Two New Hampshire state routes cross state lines while retaining their designations and NHDOT maintenance: Maine State Route 113 crosses into and out of New Hampshire twice. It runs for 1.4 mi within the town of Conway and for 4.6 mi within the town of Chatham. SR 113 remains under MaineDOT maintenance along both of these stretches.

Signage practices

State highways

State highways in New Hampshire are marked using square route shields depicting the Old Man of the Mountain. Unlike its neighboring states, New Hampshire does not use elongated shields for route markers, but uses condensed fonts for three-digit routes instead. Alternates of two- and three- digit routes (e.g. NH 115A) are signed with the parent highway's number over the letter of the alternate. For multiple alternates of the same route, the state generally uses sequential letters. With the exception of the US 1 Bypass in Portsmouth, alternates of U.S. Highways are signed as state routes. For example: NH 101E in Hampton is an exception. Despite being an implied alternate of NH 101, NH 101E has never connected to NH 101 or any of its current or former alternates. Three instances of duplicated route numbers exist in New Hampshire: New Hampshire has a few special state routes. Known examples are:

U.S. Numbered Highways

New Hampshire uses the standard U.S. Route shield, a six-point white shield over a black square background. New Hampshire contains parts of the four lowest-numbered primary US highways: US 1, US 2, US 3 and US 4. 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. New Hampshire does not use elongated route shields for U.S Routes, except on the occasional guide sign from a freeway and on some newer signage. Condensed fonts are used instead.

Interstate highways

New Hampshire uses standard-issue Interstate shields for its two-digit Interstate highways, of which there are three: I-89, I-93 and I-95. Elongated shields were not initially used for auxiliary Interstates, but such shields have appeared on newer signage. New Hampshire no longer uses its state name on Interstate shields, but older signs with the state name do exist. New Hampshire contains the only two auxiliaries of I-93: I-293 and I-393. They are both completely overlapped by other routes.

Turnpikes

New Hampshire uses a special shield on the Spaulding Turnpike and the Everett Turnpike. Both contain the name of the turnpike over a colored circle, within a rectangular shield with an arced bottom edge. The Spaulding Turnpike uses a blue color, while the Everett Turnpike uses a green color. Older shields used inverted colors, with white text and circle inside of a colored background. There is no shield for the Blue Star Turnpike, as it is only signed as I-95. However, when it was called the New Hampshire Turnpike it was signed with shields similar to those of the Spaulding and Everett turnpikes, blue in color and reading as "N.H. Turnpike".

Exit numbering

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. Exits to Interstate Highways are not assigned numbers, with the exception of I-93's Exit 15E to I-393 in Concord, which existed as such before I-393 was designated, and retained its exit number. There are a few sequential numbering anomalies:

Major junctions and route concurrencies

New Hampshire, in contrast to most other states, normally signs route junctions using green guide signs (similar to those found on freeways) instead of individual sign and shield assemblies. New Hampshire also signs nearly all route concurrencies in the same way. However, as signs are being replaced, they are now more often replaced with traditional sign assemblies.

Unnumbered state highways

Several unnumbered roads also are maintained by the state, including: