the United States' economy, defense, and mobility, from one or more of the following road networks (specific routes may be part of more than one sub-system): Interstate Highway System: The entire Interstate Highway System (which is also known as the Dwight D. Eisenhower National System of Interstate and Defense Highways) is included in the NHS, but retains its separate identity within the NHS. Other Principal Arterials: 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. (Facilities accessed include 207 airports, 198 ports, 190 rail or truck terminals, 67 Amtrak railway stations, 58 pipeline terminals as well as 82 intercity bus terminals, 307 public transit stations, 37 ferry terminals, and 20 multi-purpose passenger terminals.) Strategic Highway Network (STRAHNET): The entire network of highways which are important to the United States’ strategic defense policy and which provide defense access, continuity, and emergency capabilities for defense purposes. Major Strategic Highway Network Connectors: Highways which provide access between major military installations and routes which are part of STRAHNET. Intermodal Conectors: Routes which provide access between major intermodal facilities and the other four subsystems making up the NHS. The system includes 4% of the nation's roads, but carries more than 40% of all highway traffic, 75% of heavy truck traffic, and 90% of tourist traffic. All urban areas with a population of over 50,000 and about 90% of America's population live within of the network, which is the longest in the world. See also References External links STRAHNET description at US military's Transportation Engineering Agency STRAHNET article at the GlobalSecurity.org Weingroff, Richard F. "Backbone: Creation Of The National Highway System" National Highways System Proposed in 1913 State-by-state maps of the National Highway System of the Federal Highway Administration Highways in the United States Federal assistance in the United States 1995 in American law