The National Highway System (NHS) is a network of strategic highways within the United States, including the Interstate Highway System and other roads serving major airports, ports, rail or truck terminals, railway stations, pipeline terminals and other strategic transport facilities.
Individual states are encouraged to focus federal funds on improving the efficiency and safety of this network which makes up 4% of the nation's roads, but carries 40% of the traffic and 75% of heavy truck traffic. About 90% of America's population lives within 5 miles (8.0 km) of an NHS road. The roads within the system were identified by the United States Department of Transportation in cooperation with the states, local officials, and metropolitan planning organizations and approved by the United States Congress in 1995.
The 160,000-mile (260,000 km) National Highway System includes roads from one of more of the following road networks:
The Interstate Highway System
The Strategic Highway Network (STRAHNET) of importance to the United States' strategic defense policy including links from major military installations and this Strategic Highway Network
Access to 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
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 5 miles (8.0 km) of the network, which is the longest in the world.