National Highway System

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The National Highway System (NHS) consists of 160,000 miles of roadway that are important to the nation's economy, defense, and mobility. The National Highway System was created by the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). NHS includes the following subsystems of roadways (note that a specific highway route may be on more than one subsystem):

Caltrans' Deputy Directive #32, dated February 2004, outlines the importance of the National Highway System to the State of California.

Interstate

The plan for a network of Interstate highways connecting cities with a population greater than 1,000,000 people became a reality when President Dwight Eisenhower signed the Federal-Aid Highway Act of 1956. The Interstate Highway system was constructed but not completed. The Eisenhower Interstate System of Highways retains its separate identity within the NHS. All routes on the Interstate System are NHS.

FHWA Interstate Route Log

Non-Interstate Strategic Highway Network (STRAHNET):

This is a network of specific highways which are important to the United States' strategic defense policy and which provide defense access, continuity and emergency capabilities for defense purposes. The ability to move troops and equipment via highways to airports, ports, rail terminals, and other bases for rapid deployment is essential to our national defense. Not all highways or local jurisdiction roads are part of the NHS.

Major Strategic Highway Network connectors (SC)

These are specific state highways and local jurisdiction roads linking major military installations and other defense-related facilities to the Strategic Highway Network and highways which are part of STRAHNET. Not all highways or local jurisdiction roads are part of the NHS.

Intermodal Connectors (IMC):

These are specific highways or local jurisdiction roads that provide access between major intermodal facilities and the other four subsystems of the National Highway System are Intermodal Connectors. FHWA maintains an Official Intermodal Connectors Listing that is updated by Caltrans. Not all highways or local jurisdiction roads are part of the NHS.

OTHER NHS:

These are specific highways or local jurisdiction roads in rural and urban areas which provide access between an arterial and a major port, airport, public transportation facility, or other intermodal transportation facility. Not all highways or local jurisdiction roads are part of the NHS.