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The National Highway System includes many significant roads besides Interstate Highways

This article is about the United States highway system. See highway for links to other national highway systems.

The National Highway System (NHS) of the United States comprises approximately 160,000 miles (256,000 kilometers) of roadway, including the Interstate Highway System as well as other roads, which are important to the nation's economy, defense, and mobility. The NHS was developed by the United States Department of Transportation (DOT) in cooperation with the states, local officials, and metropolitan planning organizations (MPOs).

The National Highway System (NHS) includes the following subsystems of roadways (note that a specific highway route may be on more than one subsystem):

Interstate - The Eisenhower Interstate System of highways retains its separate identity within the NHS.

Other Principal Arterials - These are highways in rural and urban areas which provide access between an arterial and a major port, airport, public transportation facility, or other intermodal transportation facility.

Strategic Highway Network (STRAHNET) - This is a network of highways which are important to the United States' strategic defense policy and which provide defense access, continuity and emergency capabilities for defense purposes.

Major Strategic Highway Network Connectors - These are highways which provide access between major military installations and highways which are part of the Strategic Highway Network.

Intermodal Connectors - These highways provide access between major intermodal facilities and the other four subsystems making up the National Highway System .

The NHS consists mostly of existing two-lane roads. About 98% of all roads in NHS have been built. The 160,000 miles of NHS include only 4% of the nation's roads, but they carry more than 40% of all highway traffic, 75% of heavy truck traffic, and 90% of tourist traffic. About 90% of America's population lives within 5 miles of an NHS road. All urban areas with a population of more than 50,000 and 93% with a population of between 5,000 and 50,000 are within 5 miles of an NHS road. Counties that contain NHS highways also host 99% of all jobs in the nation, including 99% of manufacturing jobs, 97% of mining jobs, and 93% of agricultural jobs.

The Congress of the United States approved the NHS in 1995. Although the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) provided that certain key routes, such as the Interstate Highway System, be included in NHS, most of NHS was not specified. The Federal Highway Administration identified key routes for the NHS in conjunction with state and local transportation departments and metropolitan planning organizations.

Establishment of the NHS encourages states to focus on a limited number of high-priority routes and to concentrate on improving them with federal-aid funds. At the same time, these states can incorporate design and construction improvements that address their traffic needs safely and efficiently. States can make operational changes, such as a program to locate and remove stalled vehicles that are impeding smooth traffic flow. States can employ available technological improvements, such as Intelligent Transportation Systems (ITS), which will help reduce congestion and keep traffic moving without major, roadway expansion.

NHS is intended to be a unified system where each mode complements the other. Increasingly, intermodal carriers rely on all forms of transportation to deliver goods and services to consumers in the most efficient manner possible. NHS supports this goal by serving 198 ports, 207 airports, 67 Amtrak stations, 190 rail/truck terminals, 82 intercity bus terminals, 307 public transit stations, 37 ferry terminals, 58 pipeline terminals, and 20 multipurpose passenger terminals.

• Interstate Highway System
• Strategic Highway Network
• United States Numbered Highways
• Federal Highway Administration
• Adopt a Highway

Note: This article was adapted from public domain Federal Highway Administration web sites.

• National Highway System
• Slater, Rodney E., 1996, The National Highway System: A Commitment To America's Future, Public Roads, Spring, Vol. 59, No. 4.

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