National Highway System

The National Highway System consists of 160,000 miles (6,511 miles are in California as of 2001) of roadway important to the nation's economy, defense, and mobility. 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 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 Eisenhower Interstate System of Highways retains its separate identity within the NHS. The Story of the US Interstate - American History

Other Principal ARterials

In the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), Congress designated high-priority corridors as 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.

Non-Interstate Strategic Highway Network (STRAHNET):

The Department of Defense in cooperation with DOT, identified the non-interstate portion of the Strategic Highway Corridor Network, or STRAHNET, as critical strategic links. 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.

Major Strategic Highway Network connectors

These are highways which consist of more than 3,000 km of roads linking major military installations and other defense-related facilities to the Strategic Highway Network corridors and highways which are part of the STRAHNET.

Intermodal Connectors:

Intermodal Connectors are Important arterial highways that serve interstate and interregional travel and that provide connections to major ports, airports, public transportation facilities, and other intermodal facilities. These highways may provide access between major intermodal facilities and the other four subsystems of the National Highway System.

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