The construction of subways was first stimulated by the expansion of steam railroads and the growth of urban populations in the 19th century. The increasing automobile congestion in metropolitan areas has spurred the building of new subway systems and the extension of existing ones.
London
The world's first subway, built at the suggestion of Charles Pearson, solicitor of the City of London, was a 3.7-mile (6-km) section of the London Underground from Farrington to Bishop's Road, Paddington. The subway was begun in 1860 and completed in 1863. A method now called cut-and-cover construction was used. An arched brick structure in which the trains were to run was constructed in an open trench, earth was backfilled over the structure, and the street was then restored: Steam supplied the original motive power for the trains, so the subway had a sulfurous atmosphere. Nevertheless, it carried 10 million passengers in its first year of operation.
This successful venture encouraged additional construction, and in 1886 the City and South London Railway Company began a section of the Underground for which it used a shield developed by James Henry Greathead. The Greathead shield, a cylindrical tube of steel slightly larger than 10.5 feet (3.2 meters) in diameter and about 15 feet (4.6 meters) long, is forced forward into the ground by means of hydraulic jacks reacting against the completed tunnel lining; where water-bearing materials are encountered, compressed air is used. Because of the excellent clay underlying London, this type of construction was very well adapted to subsurface work in the city. An additional advantage of the method was that it made it possible to dig tunnels deep enough to prevent disturbance of buildings and traffic. This depth made it necessary to install elevators at the stations. Beginning in 1911, escalators superseded elevators in many stations. The deepest was that at Leicester Square (80 feet, or 24.4 meters).
The 3-mile (4.8-km) City and South London Railway, officially opened in 1890, was the first electrically operated underground railway. Electrification of other lines started in 1900, and by 1905 the last steam train had been withdrawn from service. With the use of electricity great expansion took place, and by the early 1970s London had 102 miles of underground line, including the new 14-mile (22.5-km) Victoria line, a double-track subway tunnel connecting all seven of the city's other subway lines. The London Underground system, which has a total length of about 270 route miles (435 km), is the second longest in the world, exceeded only by that of New York City.
In World War II the London Underground played an important role when its deep stations served as air-raid shelters for thousands of persons during attacks by German airplanes.
Glasgow
The second city to undertake subway construction was Glasgow, which began work on a 6.5-mile (10.4-km) circular double-track system in 1891. The cut-and-cover method was used, and the subway was opened in 1897. The Glasgow subway was mechanically operated by cables until 1935, when it was electrified.
Budapest
The first subway on the Continent was built in Budapest, where a 2.5-mile (4-km) system was opened in 1896. The subway was constructed by the cut-and-cover method near the surface of the street. Its flat roof was reinforced by steel beams spanning from the side walls, with masonry arches between the beams.
Paris
The subway in Paris, called the Métropolitan or Métro, is the third largest in the world, totaling 157 route miles (253 km). It is one of the busiest in terms of the number of passengers, with 3.3 million fares collected daily. The subway system basically consists of a comprehensive, interconnected network of 15 lines built in a circular and radial plan that gives remarkable coverage to the city.
Construction of the Métro began in 1898, and by 1900 an 8.7-mile (14-km) section had been completed; such rapid progress was made possible by the wide Parisian streets. A modified form of cut-and-cover construction, in which the street was excavated to the underside of the subway roof, was used. The roof was built in place, and the street was replaced on the new roof. Under the protection of the roof, the walls were constructed. Finally the material between the roof, walls, and floor of the subway was excavated. This method, which reduces the time that traffic is disturbed, is still used in Paris.
Berlin
Berlin, which began its subway system shortly after that of Paris, opened the first 2-mile (3.1-km) section in 1902. By 1980, the city had 72 miles (116 km) of subway. The subway system, called the Untergrundbahn or U-Bahn, consists of 11 lines, with some of the lines extending radially from the center of the city. Berlin subways handle over 200 million passengers a year.
Milan
The first subway system in Milan was opened in 1964. Television is used to check passenger flow and train operation on the 22-mile (35-km) line. The city extended its subway system in the early 1970s.
Rotterdam
The first subway in the Netherlands was a 3.7-mile (6-km) line built in Rotterdam in 1967. One section of the subway was built by sinking tubes in 37-foot (11-meter)-deep canals dug especially for them, and then filling over the area.
Boston
The first subway system in the Americas was a 1.7-mile (2.7-km) double-track line built in Boston between 1895 and 1898. Constructed principally by the cut-and-cover method, it was designed to take streetcars off the narrow, crowded streets of the downtown section. Subsequently subways were built in the city itself and between Boston and Cambridge.
New York
New York City, with the world's most extensive subway system in terms of track mileage, was a latecomer in the field. Although an experimental subway 312 feet (95 meters) long, with cars propelled by compressed air, was completed by Alfred E. Beach in the lower Broadway area in 1870, it did not prove satisfactory and was eventually destroyed. After building a number of elevated lines, which have since been removed, the city finally began a subway program in 1900. The first line, running from City Hall to Broadway and 145th Street, was opened in 1904. This section was so successful that other lines were soon started. By 1980, 237.5 route miles (390.3 km) were constructed in New York. Construction of a 63d Street tunnel linking Manhattan and Queens was begun in 1870, but work on a new Second Avenue line had to be halted in the mid-1970s because of the city's financial difficulties.
The design of New York subways is generally rectangular. Steel roof beams and columns are installed on 5-foot (1.5-meter) centers with concrete arches between them. The subways are waterproofed on the outside to protect them against leakage. Electric cables are carried inside the structure in duct banks, and the trains operate from a third rail with direct current at 550 volts. An elaborate signal system divides the trackage into blocks, so that a train in a block controls the signals and prevents another train from entering it. If a train passes a red signal, its brakes are set automatically. The safety record of New York's system has been remarkable.
San Francisco
Construction of a 71-mile (114-km) rapid transit network, including 16 miles (26 km) of subway and a 3.6-mile (5.8-km) tube under San Francisco Bay was completed in 1974. It serves the San Francisco area, including Oakland and Berkeley. Computers in Oakland make calculations for adding cars to service as needed so that every rider can be provided a seat. The project is under the direction of the Bay Area Rapid Transit (BART) District.
Washington, D.C
The Metropolitan Area Transit Authority of Washington, D. C., is responsible for a 98-mile (158-km) rapid transit system, including underground lines. The first subway section 4.6 miles (7.4 km) began operating in 1976; the second section, 12 miles (19.3 km), in 1977; and the third, 7.5 miles (12 km), in 1978. Work on the planned 47 miles (87 km) of subway was begun in 1969, and the cost was estimated at between $4 and $6 billion.
Toronto
Canada's first subway, opened in Toronto in 1954, is the 4.5-mile (7.2-km) Yonge Street line, which runs north-south. The 8-mile (12.9-km) Bloor Street line, which runs east-west, was completed in 1966 as part of an expansion program for the Toronto subway system, which uses steel-wheel cars, steel rails, and shallow cut-and-cover trenches.
Montreal
In contrast to the Toronto subway system, the Montreal system uses lightweight, rubber-tired trains that run through rock tunnels deep beneath the city streets. Montreal has 16 route miles (26 km) of subway. Two of its lines were opened in 1966; the third, in 1967.
Moscow
Moscow's first subway was constructed at a very rapid rate between 1931 and 1935 under the direction of Lazar M. Kaganovich, who conscripted a force of 75,000 workers, including many women. Various construction methods, including that used in Paris, were employed. This subway section is about 37 miles (60 km) long. It is distinguished for its elaborate marble stations, its heavy traffic, and its use of track gauge of 5 feet (1.5 meters) instead of the standard railway gauge of 4 feet 8.5 inches (1.44 meters) that has been used in other subway systems. By the early 1980s Moscow had approximately 100 route miles (161 km) of subway.
