The National Highway System (NHS) consists of roadways important to the nation’s economy, defense, and mobility.  As defined by the Federal Highway Administration, the NHS includes the following types of roads (source):

• All interstate highways.

• All routes that are part of STRAHNET, including regular and connector routes.

• Freeways and other principal arterials that provide access between an arterial and a major intermodal transportation facility. 

  • • Intermodal transportation facilities include airports, ports, railroad terminals, truck terminals, mass transit terminals, or other types of transportation facilities.

• Intermodal Connectors that provide access between the systems listed above and major intermodal facilities.

NHS routes are selected through a cooperative effort between the U.S. Department of Transportation, state and local officials, and metropolitan planning organizations (MPOs).  Note that NHS routes may be either urban and rural roads and can include both state-owned and locally-owned routes.

The Federal Highway Administration (FHWA) Highway Performance Monitoring System (HPMS) report, which ADOT is required to submit every year, includes a section that identifies roads assigned to the NHS and codes them based on the type of route it is (see Table 1).

• Code 1 includes interstates, freeways, other principal arterials, STRAHNET routes, and STRAHNET connectors

• Codes 2-9 Include NHS connector routes and identifies the intermodal transportation facility the route connects to

• Routes not on the NHS are coded 0 or left blank