TRANSPORTATION - BTS - Bureau of Transportation Statistics

The U.S. Marine Transportation System consists of waterways, ports, and their intermodalconnections. Each component is a complex system within itself and is closely linked withthe other components. Since 1975, domestic shipping has grown 16 percent by weightwhile waterborne foreign trade increased by 65 percent by weight. It is expected thatthese volumes will more than double over the next 20 years.The following sections highlight the growth across all transportation modes in the lastquarter century.Highway SystemThe United States highway network consists of 4 million miles of roads and streets. Highwaybridges also comprise a critical link in the nation’s infrastructure. At present, there are about600,000 bridges on the entire highway network [USDOT BTS 1999]. State and local governmentscontrol most roads and bridges in the United States, but all highways serve as part ofan integrated national network.The Interstate Highway System (IHS) accounts for only one percent of all highway mileage,but carries 25 percent of the total vehicle miles of travel (VMT) [USDOT FHWA 1998]. With thecompletion of the Interstate System in the 1980s, the focus shifted toward maintaining andimproving the system, improving traffic flow, and upgrading intermodal connections.Growth in the number of drivers and cars, an increase in the number of trips per household,and increased freight movement are all contributing factors to growth in highway use over thelast 25 years.In the mid-1970s, the IHS had been under construction for nearly two decades, and 37,000 ofits 42,500 miles were open to traffic. The advantages of the IHS were being felt across theentire country, and travel was increasing. Since 1975, VMT on the nation’s roads has doubled(figure 2-5). Figure 2-6 shows the change in VMT per capita for various states between 1975and 1998.Figure 2-5Vehicle-Miles Traveled (VMT): 1975-98 (Annual totals)3,0002,500Billions of miles2,0001,5001,00050001975 1980 1985 1990 19951998Source: U.S. Department of Transportation, Federal Highway Administration, Highway Statistics (Washington, DC: Annual issues).2-5