The United States highway network consists of 4 million miles of roads and streets. Traffic congestionHighway bridges also make up a critical link in the Nation's infrastructure. At present,there are about 600,000 bridges on the entire highway network. State and local governments control most roads and bridges in the United States, but all highways serve as part of an integrated national network.

The Interstate Highway System accounts for only 1 percent of all highway mileage but carries 25 percent of the total vehicle miles of travel. With the completion of the Interstate System in the 1980s, the focus shifted toward maintaining and improving the system, improving traffic flow, and upgrading connections with other modes of transportation.