rapid transit, transportation system designed to allow passenger travel within or throughout an urban area, usually employing surface, elevated, or underground railway systems or some combination of these. Rapid transit systems are generally considered to be mass transit systems, capable of moving large numbers of passengers in a single train. The large capacities of such systems make them potentially more efficient, in terms of cost and environmental effects, than automobile transportation. The principal problem to be solved in an urban rapid transit system is that of providing extra capacity to handle the volume of traffic during the morning and evening rush hours without unreasonable delays. Basically a rapid transit train consists of a number of electrically powered, self-propelled cars, each of which draws electricity from a "third rail" that runs near the tracks. Since there is an engine in each car, greater traction is produced than would be generated by a locomotive pulling a series of unpowered cars. The controls for the car motors are arranged so that an operator at either end of the train can control all of them. This arrangement eliminates involved turnarounds at the terminals.
While railways of any type may have portions of their tracks below, on, or above ground level, the term subway (or, depending on where in the world it is located, metro, underground or underground railway, or tube ) is generally reserved for systems using the arrangement of cars described above and having most of their track underground. London's underground, which went into service in 1863, is the oldest in the world; initially steam-powered, it was fully electrified by 1896, the same year that the first subway began operating on the European continent in Budapest, Hungary. Boston installed (1898) the first subway in the United States; others followed in Paris (1900), Berlin (1902), New York (1904), Madrid (1919), Tokyo (1927), and Moscow (1935). Toronto's subway, completed in 1954, was the first in Canada; Montreal's subway was completed in 1966. The Beijing system, China's first, opened in 1969; the Shanghai metro, opened in 1995, is now the world's longest. By the 21st cent. there were some 160 metropolitan rapid transit systems in the world, more than half of which were traditional subway systems. In the United States, in addition to Boston and New York, there are subways in Atlanta (1979), Baltimore (1983), Chicago (1943), Cleveland (1955), Los Angeles (1993), Miami (1984), Philadelphia (1908), San Francisco (1972), and Washington, D.C. (1976); many more U.S. cities have rapid transit systems.
Some subways consist of only a single line, but others, such as the Métropolitain in Paris, the New York City Transit system, and the London underground, are networks. The Shanghai system has the longest total route (270 mi/434 km), and the Tokyo system carries the most passengers annually (3.2 billion). By far the largest underground transportation system in the United States is that of New York City. It carries 1.6 billion people and has more than 842 mi (1,355 km) of track on 209 mi (337 km) of total route; it also has more than 6,000 cars and 468 stations—more than any other system in the world. Moscow has an elaborate subway system with tunnels 15 to 20 ft (4.5 to 6 m) high instead of the usual 10 ft (3 m). Marble was used lavishly in constructing the stations, and Russia's best-known artists participated in their decoration.
In recent years concern over urban crowding and automotive air pollution has stimulated the construction and expansion of many rapid transit systems that incorporate automated operation and magnetic-card fare systems; among the first examples were the Bay Area Rapid Transit system in California, the Metro system in Washington D.C., and a section of the London underground. See also mass transit.
See C. W. Cheape, Moving the Masses (1980); T. Rallis, City Transport in Developed and Developing Countries (1988); C. Hood, 722 Miles: The Building of the Subways and How They Transformed New York (1995); B. J. Cudahy, Under the Sidewalks of New York (2d rev. ed. 1996); S. Fischler, The Subway: A Trip Through Time on New York's Rapid Transit (1997).