In New Hampshire, roads are classified in a variety of ways for legal and management purposes.

Legislative Class
The Legislative Class of a road defines who (State or City/Town) owns a public road and is responsible for its maintainence. There are six legislative classes of public roads in New Hampshire:

Class I – Primary State System (2,347 centerline miles)
Class II – Secondary State System (2,208 centerline miles)
Class III – Recreational State Roads (48 centerline miles)
Class IV – Compact Town Roads (303 centerline miles)
Class V – Town Roads (12,019 centerline miles)
Class VI – Unmaintained Public Highways

The NH Department of Transportation is responsible for maintaining Class I, II, and III roads. Cities and towns are responsible for maintaining Class IV and V roads. Private roads are sometimes considered Class 0 roads and roads within federal lands (such as the White Mountain National Forest) are sometimes considered Class VII roads. To see how many miles of road are in your town in each legislative class, click here.


Functional Class 

Every state classifies its public roads by function, according to the Federal Highway Administration’s functional classification system:

1 – Principal Arterial – Interstate
2 – Principal Arterial – Other Freeways & Expressways
3 – Principal Arterial – Other
4 – Minor Arterial
5 – Major Collector
6 – Minor Collector
7 – Local

The functional classification of a road determines whether it is eligible for federal aid. In urban areas, class 1-6 roads are Federal Aid Eligible. In rural areas class 1-5 roads are Federal Aid Eligible. In New Hampshire, 75% of state-owned highway are Federal Aid Eligible and 6% of local roads are Federal Aid Eligible. To see a map of Federal Aid Eligible Highways in New Hampshire, click here.


Highway Tiers

State-owned roads are further classified into Highway Tiers, based on similarities like connectivity, regional significance, and winter maintenance requirements. These tiers are as follows:

Tier I – Divided Highway System (844 centerline miles)
Tier II – Arterial Roadway System (1426 centerline miles)
Tier III – Regional Corridors (1438 centerline miles)
Tier IV – Local Connectors (895 centerline miles)
Tier V – Local-Owned Roads (12,019 centerline miles)

To see the tier of each state-owned road in the state, click here.


National Highway System

The federal designated National Highway System comprises 1,256 miles of the State’s highway system, including Interstates, Turnpikes, and other priority highways. In Northern New Hampshire, this includes Interstate 93, US 2, US 302, and NH 16. To see a map of the National Highway System in New Hampshire, click here.


Maintenance Strategies

The NHDOT Pavement Strategy prioritizes highways based upon their Tier. NHDOT defines four strategies for maintaining road surfaces – maintenance paving, preservation paving, rehabilitation projects, and reconstruction projects. Frequent low-cost maintenance or preservation paving can prevent road surfaces from deteriorating to such bad conditions that they need higher-cost rehabilitation or reconstruction. NHDOT considers the long-term life cycle costs of maintaining roads when it decides how many miles of road within each highway tier should be maintained with each strategy. NHDOT uses a survey vehicle to measure pavement condition by roughness on a two-year cycle. To see a map of pavement condition (as of 2016) on state roads, click here.

The NHDOT Bridge Strategy also defines four strategies for maintaining bridges – maintenance, preservation, rehabilitation, and reconstruction. Like with paving, regular maintenance and preservation work is lower-cost and extends the service life of bridges. Reconstruction of bridges when they reach the end of their service life is very costly, so the NHDOT evaluates each bridge to determine whether is should be reconstructed, down-posted, or closed. The NHDOT prioritizes bridges based upon their highway tier, and has an additional class of bridges – High Investment Bridges – that include the largest and most costly bridges (eg. Memorial, I-95, Amoskeag, etc.).

NHDOT regularly inspects state-owned and local-owned bridges. To see the condition of each bridge in the state, click here. To visit the NHDOT Bridge Design webpage, click here.