Interstate Highway System

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INTERSTATE HIGHWAY SYSTEM. The Dwight D. Eisenhower System of Interstate and Defense Highways includes more than 46,000 miles of intercity highways. With just 1 percent of U.S. highway mileage, the interstate system carries 21 percent of highway travel, including half of all heavy truck travel. The interstate is a major economic asset, and high design requirements have helped to make it the world's safest highway system. The states own and operate most highways; the interstate is a national system of state highways. The program made federal funds available for specific activities to encourage states to pursue federal interests in national defense and interstate commerce, though commerce always has been more central to the program.

The Federal-Aid Highway Act of 1944 first authorized a 40,000-mile interstate as part of the Federal-Aid Primary System, established in 1921. In 1947, the Bureau of Public Roads designated 37,681 miles, with 2,900 miles in urban areas. Another 2,319 miles were reserved for urban distribution routes and circumferentials (beltways). However, the 1944 act dedicated no funds for the inter-state system and applied the Primary System's principle of covering 50 percent of costs with federal money. Without dedicated funds or a higher federal share of costs, no projects emerged. In 1952, Congress authorized $25 million annually for fiscal years 1953 through 1955, then $175 million annually for 1956 and 1957, with a 60 percent federal share. A few projects got under way, with $5.6 million spent in 1953, increasing to $90 million in 1956.

The Federal-Aid Highway Act of 1956, under President Eisenhower, established the "real" interstate program.

Congress added 1,000 miles to the system, established a trust fund, and raised the federal share of project costs to 90 percent. Funding increased to $1 billion in 1957, with accelerating authorizations through 1969. Congress also added 1,500 miles in 1968, bringing the total to 42,500 miles. Another several hundred miles were added as "continuation" mileage, but these links were not eligible for interstate funds. With new funding and high federal shares, construction began in earnest. Expenditures reached $1.25 billion in 1958 and nearly $2 billion in 1959. At $2.6 billion in 1963, the interstate accounted for 73 percent of all Federal Highway Administration (FHWA) expenditures. Outlays increased steadily, peaking at $4.1 billion in 1986 and 1988, though the program had slipped to less than 50 percent of all FHWA outlays.

The interstate program enjoyed strong public support, but some groups soon characterized it and the urban renewal program as "urban removal" of low-income neighborhoods. Early criticism was perceived as "obstructing progress," but opposition increased among the displaced, environmentalists, academics, and others, especially over new urban projects, some of which were never built. In response, beginning in 1962, Congress steadily increased the role of local governments in the program, particularly in urbanized areas, and increased planning requirements to ensure consideration of environmental effects and transit alternatives. After 1973, states needed local governments' approval for urban interstate projects. Later, with local agreement, states could transfer funds from one highway program to another and could finance transit construction with interstate funds. The interstate program financed much of the subsequent expansion in urban rail systems. Congress also raised the federal share on noninterstate highways to 70 percent in 1973, then to 80 percent, equaling the federal share for transit construction.

Simultaneously, most of the interstate system approached completion. By 1980, the goal of a new system of "superhighways" had essentially been achieved. Controversial urban links accounted for most remaining mileage. In 1981, Congress began redirecting funds from new construction to preservation through resurfacing, restoration, rehabilitation, and reconstruction of existing mileage ("4R"). Bridge replacement needs also began to reduce the role of new interstate construction.

Finally, the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991 fundamentally restructured the entire federal-aid highway program. Those changes have been reinforced in subsequent acts. The ISTEA established a 155,000-mile (260,000-kilometer) National Highway System of arterial highways, including the interstate as a distinct subset. The ISTEA also authorized forty-two "high-priority corridors," some of which have been added to the interstate system. However, new construction was no longer a core objective. The federal share on interstate projects changed to 90.66 percent for

4R, and 86.5 percent if projects added capacity other than high-occupancy vehicle lanes. Construction for new capacity fell to just $363 million in 1999, while total inter-state spending ($3.2 billion) fell to 15.7 percent of total FHWA spending. Nevertheless, the interstate remains a monumental public works program that met its goal of providing a national system of safe, high-performance highways.


Cox, Wendell, and Jean Love. The Best Investment a Nation Ever Made. Washington, D.C.: Highway Users Federation, 1996. A history of the interstate system and an assessment of its economic and social benefits.

Gomez-Ibáñez, José, William B. Tye, and Clifford Winston. Essays in Transportation Economics and Policy. Washington, D.C.: Brookings Institution, 1999. A discussion of contemporary issues confronting transportation in general in the United States.

Highway Statistics. Washington, D.C.: Federal Highway Administration, 1947–. Annual publication providing data on highway mileage, travel, and finance.


See alsoFederal-Aid Highway Program ; Infrastructure ; Roads ; Transportation and Travel .

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Interstate Highway System

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