National Highway System, Intermodal Connectors, and Principal Arterials: 2018
NHS = National Highway System or the interstate highway system; STRAHNET = Strategic Highway Network or a network of highways that are important to the U.S. strategic defense policy. MAP-21 principal arterials = those rural and urban roads serving major population
centers not already categorized above.
This map is included in the Transportation Statistics Annual Report 2020 publication.
U.S. Department of Transportation (USDOT), Federal Highway Administration, Highway Performance Monitoring System, as cited in USDOT, Bureau of Transportation Statistics, National Transportation Atlas Database, available at www.bts.gov as of September 2018.