Road systems and freeways
Road systems and freeways (Encyclopedia of Environmental Issues, Revised Edition)
The era of the freeway began during the 1950’s, when lobbying groups in the United States encouraged a political vision of a nationwide high-standard, high-speed road network. Retired U.S. Army general Lucius D. Clay led a committee that studied transportation needs across the United States and advised President Dwight Eisenhower that the nation needed what came to be called the National System of Interstate and Defense Highways. The costs of creating and maintaining the more than 69,000 kilometers (43,000 miles) of interstate highways built after 1956 have been shared by federal and state governments on a 90/10 (federal/state) matching basis. The federal share comes from the Highway Trust Fund, which receives revenues from federal taxes on fuels, lubricants, vehicles, and vehicle parts. Although the interstate system accounts for only 1 percent of the total road miles in the United States, it carries 20 percent of the traffic.
Studies of the U.S. road and highway systems as a whole—including local roads and services—have found that motor vehicle user fees cover only two-thirds of public expenditures, not including the substantial nonmonetary external costs of environmental impacts. Because many of the costs of using private vehicles are hidden, many Americans perceive driving their own cars to be less expensive than using public-transit alternatives. U.S. highway statistics for 2008 indicated the existence of more than 248 million...
(The entire section is 340 words.)
Environmental Impacts (Encyclopedia of Environmental Issues, Revised Edition)
Air pollution constitutes the most serious environmental impact caused by highway transportation. Developments that may generate traffic, such as parking lots for shopping centers, may be classified as indirect sources of pollution. Internal combustion and diesel engines are the principal sources of carbon monoxides and hydrocarbons, account for nearly one-half of the nitrogen oxides, and are the chief source of particulate lead in the atmosphere. Highway emissions are directly related to traffic volume and density, vehicle type, speed, and mode (idle, acceleration, cruise, or deceleration). Increased speed produces a demand on an engine for increased power, which leads to more fuel consumed and greater emissions, but the vehicle also passes through an area more quickly. Long trips by motor vehicle and traffic congestion both increase the emissions discharged into the atmosphere.
The building of roads and highways also consumes open space, affecting plant and animal life, as well as climate and water runoff. Highways facilitate the spread of urban areas and often lead to low-density developments, which are difficult to provide with services. Highways that connect developed areas usually follow valleys and other areas with flat terrain, and consequently highways are often built in close proximity to streams, lakes, and wetlands. Until very late in the twentieth century, hydrologic features that blocked proposed roads...
(The entire section is 551 words.)
Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Goddard, Stephen B. Getting There: The Epic Struggle Between Road and Rail in the American Century. New York: Basic Books, 1994.
Gonzalez, George A. The Politics of Air Pollution: Urban Growth, Ecological Modernization, and Symbolic Inclusion. Albany: State University of New York Press, 2005.
Hester, R. E., and R. M. Harrison, eds. Transport and the Environment. Cambridge, England: Royal Society of Chemistry, 2004.
Lay, M. G. Ways of the World: A History of the World’s Roads and of the Vehicles That Used Them. New Brunswick, N.J.: Rutgers University Press, 1992.
Lewis, Tom. Divided Highways: Building the Interstate Highways, Transforming American Life. New York: Viking Press, 1997.
(The entire section is 103 words.)