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Rapid transit began with the opening in 1863 of the Metropolitan Railway, now part of the London Underground. However, the smoke caused discomfort for passengers in operating steam trains through tunnels and limited the appeal of this mode of transport. Between 1863 to 1890 there were numerous proposals to build pneumatic or cable-hauled railways in London to overcome this problem, but none proved successful. Smoke was less of a problem in steam-hauled elevated railways, starting with the West Side and Yonkers Patent Railway in New York City in 1870 (although this line opened unsuccessfully as a cable-hauled railway in 1868). The opening of London's City & South London Railway in 1890 overcame the smoke problem by using electric traction and led to the development of electric underground railways in Liverpool, Budapest, Glasgow, Boston, Paris, Berlin and New York City by 1904.
First tunnels 
Before any plans were made for transit systems with underground tunnels and stations, several railway operators had used tunnels for freight and passenger trains, usually to reduce the grade of the railway line. Examples include Trevithick's Tunnel from 1804, built for the Penydarren locomotive, the 1829 Crown Street Tunnel at Liverpool and the 1.13 miles (1,811 metres) long 1836 Lime Street Tunnel also at Liverpool, of which a part is still used today making it the world's oldest used tunnel.
The first urban underground railway was the Metropolitan Railway, which began operations on January 10, 1863. It was built largely in shallow tunnels (see more at cut and cover) and is now part of the London Underground. It was worked by steam trains, and despite the creation of numerous vents, was unhealthy and uncomfortable for passengers and operating staff. Nevertheless, its trains were popular from the start and the Metropolitan Railway and the competing Metropolitan District Railway developed the inner circle around central London (completed in 1884) and an extensive system of suburban branches to the northwest (extending into the adjoining countryside), the west, the southwest and the east (mostly completed by 1904).
The first electrified urban railway, London's City & South London Railway underground railway, opened in 1890, in deep tubular tunnels, leading to the term "tube", which was eventually applied to the London Underground. It was originally planned to be cable-hauled, but the bankruptcy of the company that contracted to supply the cable-haulage technology forced the railway company to consider the brand-new technology of electric traction, because its Parliamentary Act prohibited use of steam power. It operated locomotive-hauled trains with three carriages, initially without windows, because it was considered that passengers would not need to know where they were if they were in tunnels.
The UK's only elevated railway opened in 1893 in Liverpool. The Liverpool Overhead Railway was the world's fourth oldest metro and was the world's first fully formed elevated railway to run electric trains from the start. The LOR pioneered Electric Multiple Units of three car trains. Automatic and electric light signals was also a first for the railway. The presence of the "El" was one aspect that earned Liverpool the nickname of "Britain's North American City". The LOR was demolished in 1957 with Liverpool today served by a partially underground urban rail network known as Merseyrail.
A major breakthrough in the development of modern electrically driven rapid transit occurred when the American inventor Frank J. Sprague successfully tested his system of multiple-unit train control (MUTC) on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. MUTC, which allowed all the motors in an entire train to be dependably controlled from a single point, freed rapid transit systems from dependence on locomotive-hauled coaches.
Early systems in the West 
Istanbul Tünel (English: Tunnel ) is one of the worlds oldest short underground railway lines in Istanbul, Turkey. It is an underground funicular with two stations, connecting the quarters of Karaköy and Beyoğlu. Tunnel construction works started on June 30, 1871. On July, 1872 British company "The Metropolitan Railway of Constantinople to the Galata Pera" was registered. On December 5, 1874 the construction was completed and started carrying people on January 17, 1875.
Budapest inaugurated the first electrified underground line on the continent, the M1, in 1896. It ran from Gizella tér (now Vörösmarty tér, the city centre) to City Park and the local zoo, a distance of 3.7 kilometres (2.3 mi). It is now part of the Budapest Metro and has largely been restored to its original condition. The Budapest system was also the first electric underground railway with overhead cables rather than the more common third rail system. The 10.4 kilometres (6.5 mi) Glasgow Subway in Scotland opened the same year and used cable haulage until it was electrified in 1935.
The first line of the Paris Metro opened in 1900. Its full name was the Chemin de Fer Métropolitain, a direct translation into French of London's Metropolitan Railway. The name was shortened to métro, and many other languages have since borrowed this word. The Berlin U-Bahn (for underground railway) opened in 1902; because large sections of the line were elevated, it was also called Hochbahn (high railway) until the 1920s.
Although not built as a metro system, the Ferrovia Cumana, opened in 1889, and running in tunnels under the city of Naples, today forms part of Napoli's subway system as Line 2, making it the oldest section of a rapid transit system in Italy. The first purpose-built Italian rapid transit system was built for the 1906 Milan International Exposition. It was an elevated light rail that linked the two main areas of the fair. The line was dismantled eight years later.
The Americas 
Boston has the oldest subway tunnel in the United States that is still in use, part of the Green Line downtown, dating from 1897. The original construction was a short four-track tunnel, with only two stations downtown, built to take light rail cars from outlying areas off the streets. Later subways in Boston carried full-size trains; the Green Line still operates with light rail equipment. In 1901, heavy rail trains began to use the tunnel as part of the original configuration of the Main Line Elevated, the first elevated railway in Boston.
The New York City Subway, which has become one of the world's largest, did not open its first section until 1904, but this was a fully independent four-track line, stretching 9 miles (14.5 km) from City Hall to 145th Street. Extensions were soon built, reaching the Bronx and Brooklyn; this is now part of the IRT system. Two major subway systems, operated by the BMT and the IND were constructed later, and many pre-existing elevated railway lines were incorporated into the BMT and IRT systems. The Hudson and Manhattan Railroad, which also opened a subway tunnel in Manhattan in 1908 and connected with New Jersey, remained a separate railroad company, and later came under the control of the Port Authority of New York and New Jersey as the Port Authority Trans-Hudson (PATH). Some New York City subway lines run on right-of-way first used in 1863 by railroads, and converted R44 subway cars run on the 1860 Staten Island Railway.
The oldest subway in the Southern Hemisphere, "Subterráneos de Buenos Aires", opened in 1913 in Buenos Aires, Argentina, which is also the oldest one in Latin America and the Spanish-speaking world. The "Buenos Aires Underground", colloquially and officially known as el Subte, and particularly Line A, with its magnificently preserved "La burgeoise" wood and metal carriages, have been in continuous operation for 100 years (as of 2013), carry 190,000 passengers daily, and are a tourist attraction as well. This line is converted from an underground tramway. These cars are to be taken out of service by the end of January 2013.
The interwar period saw the first metros established at the periphery of the continent: The Madrid Metro opened on October 17, 1919 under the direction of the Compañía de Metro Alfonso XIII. Metro stations served as air raid shelters during the Spanish Civil War. Today, Madrid's subway is one of the longest systems in the world. Barcelona Metro followed in 1924.
The first underground in the USSR (in Russian метрополитен metropoliten or метро metro) opened in 1935 in Moscow. The first line — between Sokolniki and Park Kul'tury — was 11.2 km long. And the projects of two of the first stations, Krasnye Vorota and Mayakovskaya, was awarded a Grand Prix at the 1937 and 1939 World's Fairs in Paris and New York. The Moscow metro is one of the most elaborately decorated undergrounds of the world, with its stations (especially built in the Joseph Stalin epoch) often being called underground palaces. As of 2012, the Moscow metro has 308 kilometers of railways and 186 stations and is one of the busiest metro in the world. In Russia and other republics of the former Soviet Union as a whole, subways opened in Saint Petersburg (1955), Kiev (1960), Tbilisi (1965), Baku (1967), Kharkov (1975), Tashkent (1977), Yerevan (1981), Minsk (1984), Nizhniy Novgorod (1985), Novosibirsk (1986), Samara (1987), Yekaterinburg (1991), Dnipropetrovsk (1995), Kazan (2005) and currently are underfunded, slow construction in some other cities. In Volgograd and Kryvyi Rih in 1980s a "metrotram" opened – it runs underground, along with common city trams.
After some stagnation, in the late 20th century many new European metros, some driverless and tired, appeared in non-large cities, especially in Spain, France and Italy.
The Americas 
The Toronto Subway opened in 1954. One experimental trainset consisted of the first aluminum subway cars, which reduced weight and therefore operating costs. With the next car order in 1963, only aluminum was used. The new cars, at 75 feet/23 m, were at the time the longest in the world. The Montreal Metro, was the second subway system in Canada and was inaugurated in 1966 as part of Expo 67 that would be held in Montreal.
In Brazil, the first underground opened in 1974 in nation's largest city and economical "capital" São Paulo, and now well busily carries some four million passengers on an average weekday as part of the São Paulo Metro. Part of it consists of converted older railways; some of its stations actually date from the 1880s. Underground lines have been built also in Rio de Janeiro, Belo Horizonte, Recife, Porto Alegre and capital Brasília.
Metro de Santiago is the metro system serving Santiago, the capital of the Republic of Chile. It is a network of five lines with a total of 85 stations, and the only South American rubber tired metro.
Non-capital Medellín, Colombia is served by one of the few profitable metro systems in the world. Operated by the Metro de Medellin Company, moves less than 500.000 passengers a day. This system operates in elevated infrastructure in downtown area and on-level parallel to the river. The construction of the system had astronomical cost overrun that lead to a great public debt, that still is in the budget.
Bay Area Rapid Transit (BART) in the San Francisco Bay Area and The capital's Washington Metro in Washington, D.C. opened in 1972 and 1976 respectively, as part of changing attitudes towards transportation in the United States, leading to subway and LRT systems opening in many cities that had done without.
The most recently completed fully underground heavy rail metro line in North America is the LACMTA Red Line in Los Angeles, which goes from Union Station in downtown Los Angeles, through the mid-Wilshire area, East Hollywood, central Hollywood, and ending 17 miles away in North Hollywood in the San Fernando Valley. Construction was started on this line in 1986 and completed in 2000. In autumn 2005, several politicians including Los Angeles mayor Antonio Villaraigosa indicated a desire to complete the originally conceived subway route along Wilshire Boulevard to West Los Angeles and Santa Monica. Phase One to La Cienega Blvd has been approved. http://www.metro.net/projects/westside/
China's first subway system, Beijing subway, began operation in 1969 only. Tianjin (1984), Shanghai (1995), Guangzhou (1999), Wuhan (2004), Shenzhen (2004), Nanjing (2005), Dalian (2005) and some other cities also have rapid transit systems in operation.
In 1979, now Chinese Hong Kong's subway line, the MTR, began operations. It currently has nine lines, including four that run underneath Victoria Harbour. By 1982, the British section of the Kowloon-Canton Railway, then known as KCR East Rail, started to provide metro-like service upon electrification was completed. 2007 saw the merger of KCR into the MTR system.
India is rapidly expanding their urban rail systems as well and notable that first rapid systems appeared not in capital. India's oldest usual metro is in Kolkata preceded by elevated rapid transit Chennai MRTS. Capital Delhi was the third only. Other cities like Mumbai, Bengaluru, Chennai, Hyderabad carries a construction of metros. Recently Patna and some other cities has hired engineers and civil planners to find a location of future metro lines.
In the past 30 years, a number of cities in South Korea have also developed modern and extensive subway systems. The largest, Seoul, has twelve lines over approximately 314 km of track. Busan, Daegu, Incheon, Daejeon and Gwangju also have subway systems. Seoul & Incheon is connected by metro.
1987 saw the Mass Rapid Transit in Singapore open. It was the world's first heavy rail system to feature platform screen doors. The country made news again by having the world's first automated heavy rail system. The network has four lines with another one to be ready by 2013.
In Saudi Arabia not in capital, but in Mecca, a 20 km first line of ground and elevated metro system was completed in 2011. A total of 5 metro lines with long trains are planned to carry mass of pilgrims to the religious sites. Another two similar ground metros are under construction in Riyadh (capital) and Jeddah (economical "capital").
Some other Asian countries has or constructs metros or metro-like monorails also.
Cairo since 1987 is the first African city with a metro system, partly converted from a railway line. It is currently under development. Modern tram system of Tunis called metro but is not a rapid transit. Second African metro will be Algiers. Pretoria, Lagos and some other African cities has plans for building a metro network.
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