National Highway System
The National Highway System includes the Interstate Highway System as well as other roads important to the nation's economy, defense and mobility.
The National Highway System (NHS) was developed by the Federal Department of Transportation in 1995 in cooperation with the states, local officials and metropolitan planning organizations (MPOs).
The NHS consists of NHS routes, intermodal facilities and intermodal connector routes where required for travel from the NHS routes to the intermodal facilities. Routes designated as Strategic Highway Network (STRAHNET) by the Department of Defense also form part of the NHS.
There have been only minor changes to the NHS until the Moving Ahead for Progress in the 21st Century Act (MAP-21) was authorized by congress and signed into law in 2012. MAP-21 resulted in the addition of 1,200 miles of Washington roads to the NHS.
Washington NHS routes are maintained in Washington’s Highway Performance Monitoring System (HPMS) and represented in Washington’s HPMS spatial network (GIS). Changes and updates to the NHS are reported to FHWA annually.
NHS documents
Washington State Highway NHS List (PDF 7.18MB)
Washington Local Agency NHS List (PDF 1.0MB)
| NHS Routes: | Centerline Miles | Lane Miles |
| State Highway (including Interstate) | 3,576 | 11,416 |
| Local Agency | 979 | 3,329 |
| Total | 4,555 | 14,745 |
| NHS Routes: | Centerline Miles | Lane Miles |
| Interstate only | 764 | 4,020 |
Note: Mileages do not include proposed (unbuilt) NHS
Changes to Washington’s NHS
Changes to the NHS must meet the federal guidance criteria detailed in US Code, Title 23 Part 470 Highway Systems and involve WSDOT, affected local and regional officials, and metropolitan planning organizations and the FHWA WA Division Office. Formal approval of changes to the NHS is issued by the FHWA Office of Planning. Changes to Washington’s approved NHS are managed by the WSDOT HPMS Section.
NHS map and data download
View the current NHS routes in the WSDOT National Highway System (NHS) Map Viewer, or download a copy of the data from the WSDOT Open Data Portal:
• WSDOT - National Highway System for State Routes
• WSDOT - National Highway System for Non-State Routes
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Improved access to 98.2 miles of upstream fish habitat
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28% increase in the value of exports and imports
from $90.2 billion in 2020 to $115.5 billion in 2021.