The National Highway System (NHS) is approximately 223,000 miles of roadway important to the nation's economy, defense, and mobility. The NHS includes the following subsystems of roadways.
- NHS Interstate: The Eisenhower Interstate System of highways retains its separate identity within the NHS.
- NHS Routes: These highways are secondary to the NHS Interstate, but still remain important to the national economy, defense and mobility.
- NHS Intermodal Connectors: These highways provide access between major intermodal facilities and the other subsystems making up the National Highway System.
The NHS encourages transportation planners to focus on a limited number of high-priority routes and to concentrate on improving them with federal-aid funds. At the same time, states can incorporate design and construction improvements that address their traffic needs safely and efficiently.
Wisconsin has approximately 5,955 miles of NHS roadways. Available on the WisDOT FTP server are urban(ized) area maps reflecting the additions to the NHS made through the 2012 MAP-21 Surface Transportation Authorization Bill. Some additional changes were made in 2016 to eliminate non-essential routes that were added because of MAP-21, and to look at new principal arterials based on 2010 census data. Also available on the FTP server are the intermodal connector maps and planned route detail maps.