There are more closed sections of metro or metro-like lines in the world than you might imagine!
New York City has abandoned an entire metro system — and a fairly substantial one at that! Apart from the metro and subway sections listed below, four freight-only urban underground lines have been abandoned, three mail lines in London, and the extensive general merchandise system in Chicago. And there are of course a fair few stations that have closed, and short sections of line that have been realigned, on various systems. Madrid, Paris and Berlin have all had line numbers that have disappeared and subsequently been reused elsewhere on the network — although probably hardly any significant mileage was lost when these line numbers first disappeared. List compiled and complemented from a post by User MetroGnome.
Berlin had 15 stations in the middle of the city closed after the wall went up in 1961, but these have now all re-opened since 1989. The sections of the Western network that passed under East Berlin were: Stadtmitte to Schwartzkopffstr. (line U6), Bernauer Str. to Heinrich-Heine-Str. (line U8), Potsdamer Platz to Nordbahnhof (lines S1, S2). During that period, all trains on those lines were pulling slowly through the dimly lit stations, where occasionally one or two armed GDR soldiers could be seen guarding the empty platforms.
Boston once had an elevated line above city streets - elevated in the suburbs, with two alternative routes (one elevated, one underground) across the central area. This has gradually evolved into the present Orange Line of the subway. The central elevated route closed in 1938 without replacement, while the northern section was replaced by the current section of Orange Line (alongside a main line railroad) in 1975. The southern section was "replaced" in 1987 by a section of Orange Line subway on a somewhat different alignment - so different, in fact, that more recently part of the Silver Line (a conventional bus route, but marketed as if it were a subway line) has been introduced on the streets that the Orange Line once ran above. So, the only original section of line left is the underground section (and even that isn't quite original - elevated trains had to run through streetcar tunnels initially, while this section was finished). The last short section of elevated alignment in the city - actually part of the light rail Green Line - went in 2004. Boston has recently also got rid of an elevated freeway through the city centre, replacing it with road tunnels ("The Big Dig"). A streetcar or tram tunnel has been partly or wholly abandoned.
Campinas LRT, popularly known as Pre-Metro, was a transit system which operated between 1990 and 1995. It has been 7.9 km long with 8 stations and a fleet of 3 trains, carrying about 4,000 passengers per day.
Chicago has lost a number of suburban sections of its elevated network over the years, only some of which were replaced by new subway lines operating in vaguely the same areas. Chicago had a full-scale elevated railroad within a World's Fair site in the 1890s, which didn't last very long. A streetcar or tram tunnel has been partly or wholly abandoned.
The Tandy Center Subway operated in Fort Worth, Texas, from 1963 to 2002. It ran a distance of 0.7 miles (1.1 km) and was, during the period of its operation, the only privately owned subway in the United States.
Glasgow had a number of main line railways (with some metro characteristics) built beneath its streets - one has been continuously in operation, one permanently closed in the 1960s but was reopened in the 1970s, and one (branch line) remains closed. A surface suburban network was built by a main line railway in nearby Paisley at the start of the last century, but (owing to sudden, unexpected competition from electric trams, which appeared just before it was due to open) it never carried passengers. In the 1930s, the main line railway from Finsbury Park to Alexandra Palace was partially converted to London Transport standards (in order to be taken over by the Underground), but this scheme was later abandoned and the line has since closed.
The Peachliner, formally the Tokadai Shin-kotsu Peach Liner was a people mover with 7 stations and a length of 7.4 km. It operated from 1991 until September 30, 2006, when it became the first people-mover system in Japan to cease operations.
Liverpool's Mersey Railway began life in the 1880s effectively as a metro system, but by the 1940s had been fully absorbed into the main line network. As far as I know, no other city in the world has a former part of its metro network now in the hands of railway preservationists.
Closed sections of the London Underground network:
1. Acton Town – South Acton (28 February 1959). This short branch of the District line had been worked as a shuttle with single-car trains from 1932 until closure.
2. Holborn – Aldwych (30 September 1994). This was a short in-town branch of the Piccadilly line left over from a merger of two separate schemes during the construction phase. It was worked a shuttle for most of its active life. The line still exists and is used for filming and other special purposes.
3. Epping – Ongar (30 September 1994). The outer end of a former main line railway this line had steam-worked trains connecting with the Central line services from Epping to central London from 1949 until its electrification in 1957. It never had a regular service under London Transport operation to the centre of London and housing development in the area it served was not permitted after the war. Following closure to normal passenger traffic it has subsequently been restored as a steam operated heritage railway.
4. Green Park – Charing Cross, closed in 1999 with a new Charing Cross opening. It must have been the shortest-lived part of London Underground as it was only used for passenger traffic between 1979 and 1999 when the Jubilee line was diverted via Westminster and Waterloo on its way to Stratford.
In 2008, a portion of meter-gauge LRT tunnel with the underground stations LU-Rathaus, Danziger Pl., Hbf., and Ostausgang has been closed. London, Paris and New York have all closed underground sections of lines, although none as long as the section closed in Ludwigshafen.
Expo-Express, while purpose-built for Expo 67, was a surprisingly robust, metro-like elevated system, using standard railway technology, with stations about 120 metres long. It served not only the islands on which the expo was held but also the mainland (Place d'Accueil and Habitat 67 stations). After the end of the exhibition proper, several of the pavilions stayed open for some years, and Expo-Express was sold to and operated by the Commission de transport de Montréal, like the metro and buses. The mainland section was closed by 1969 but a station was actually added (Notre-Dame East) at the same time. By the end, though, it was only operating 2 months a year and was finally closed in 1972. Today, the only vestige left is a rail bridge crossing Le Moyne Channel at the east end of Île Notre-Dame, just east of the Jacques Cartier Bridge.
In 2010, service to Rigaud on what was then the Dorion-Rigaud commuter train line was discontinued.
New York City once had a major network of elevated lines. In Manhattan, there were four principal lines (three running the whole length of Manhattan Island, and a fourth branching off one of the others and then running on its own for most of the length of the island), which extended into neighbouring boroughs. The origins of the network dated back to 1868. Some sections were directly replaced by new subway lines, while others were abandoned without replacement. Three of these lines closed between 1940 and 1942, with the fourth surviving until 1955. Remnants of the network in other boroughs survived longer - the last line in Brooklyn closed in 1969, and a short branch in the Bronx remained until 1973. Although at times there was common ownership, through ticketing, and limited through running with the subway network, the elevated was effectively a separate system. While some sections of the current subway network are also on elevated alignments, these use more substantial structures that can support the weight of the steel-bodied rolling stock that is needed for running underground; the "true" elevated system used lighter structures, which could only support the wooden-bodied cars that were hence banned from running into the subway. I'd guess that, in terms of mileage, more metro alignment has been abandoned in New York City than in the rest of the world combined. A streetcar or tram tunnel has been partly or wholly abandoned.
SATU (Sistema Automático de Transporte Urbano) was a driverless urban cable rail system in Paco de Arcos, Oeiras. It was inaugurated on 7 June 2004 and ran just over one kilometer. Extensions were planned to open in 2015 and 2017, but due to liquidation of the operator quit service in early 2015.