Subway
As cities have become increasingly congested with vehicular traffic, mass transit systems have been developed to relieve traffic jams, taking passengers to their destinations without the need for automobiles. Subways serve as the nucleus of many transit systems and are generally underground rail lines that offer commuters a relatively speedy ride to and from urban centers. In most cases, the subway forms the nucleus of a larger network of ground-level and above-ground train and bus lines.
Two types of rail subways exist, the open-cut and the tubular. The open-cut subway is constructed by digging a trench, then covering it after the tunnel structure has been put into place. Open-cut subways are rectangular in shape.
The tubular subway, or tube, is constructed by boring a round linear hole parallel to the ground surface. The surface is penetrated only for passenger stations and ventilation shafts.
The first tunneling shield—a means of supporting the ground as workers tunnel through the earth--was patented in Great Britain in 1818 by its inventor, Marc Isambard Brunel. Later shields also were devised by Peter William Barlow and Englishman James Henry Greathead (l844-l896) in the nineteenth century, all of them comprising technology crucial to the development of the subway.
Subways are usually built in alignment with existing streets since the sublevels of office buildings can obstruct any alternative. Beyond the city center, the trains may go in any direction and run beneath rivers and harbors.
Some subways, like Montreal's Metro, run several levels below the city center, with the upper levels used for shops, offices, museums, and hotels. Construction costs, which can be millions of dollars per mile, make subways impractical in less densely developed areas.
The first subway, suggested by city solicitor Charles Pearson, opened in London in 1863; that initial 3.75 mi. (6.033 km) was constructed by the open-cut method and carried 9,500,000 passengers in its first year. Passengers were first carried by steam locomotives that burned coke and coal, both major pollutants, but electricity was in use by 1890. All subways built since then have used electric trains, which are quieter and do not foul the subway passages with pollution. In l866 work began on what became known as "The Tube" after tunneling methods and shields were perfected. American financier Charles Tyson Yerkes (1837-1905) came to London in l900 to construct additional tube rail lines and electrify the open-cut segments.
In 1896, Budapest, Hungary, became the first country in continental Europe to open a subway; the Paris Metro opened four years later. Boston opened the first subway in the United States in 1897, and the New York subway system was begun in 1904 and is now the largest system in the world. Dozens of other subway systems have been built in cities worldwide. San Francisco's Bay Area Rapid Transit System (BART), built in 1971, was the first fully automated subway system, eliminating the use of human drivers.
In many cities in the United States, the migration of major employers to suburban areas has posed a new challenge to transit planners. Despite this, the subway will remain a permanent part of the urban scene.
This is evidenced not only by the 1990s completion of a subway that extends throughout the Washington, D.C. metropolitan area and the beginning of one in Los Angeles, but by the 1997 commitment of the nation's largest rapid transit system (serving metropolitan New York) to purchase a fleet of 1,080 state-of-the-art subway cars that will bring their system into the 21st century. In 1998, New York began ordering the most technologically advanced subway cars ever built. These sleek, rider-friendly cars have improved interior space, seating, and information systems, as well as more and better safety features and a smoother ride. Called the R142, the new car is equipped with computer-based communications and diagnostics systems that will interact with an onboard monitoring system. Passengers in these new cars will enjoy ample, bench-style seats and use wider doors. Electronic signs and prerecorded announcements will keep passengers informed. Roof-mounted air conditioning units also will be more reliable, and energy absorbing "crush zones" at each car end will keep travellers safe. Even the operator's cab is ergonomically designed. Tomorrow's subways will run faster, closer together, safer, and with less breakdowns.
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