Premetro

A premetro is a tramway or light railway which includes segments built to rapid transit standards, generally as part of a process of conversion to a metro-standards railway usually by the construction of tunnels in the central city area.

The first city to carry a portion of a streetcar line through the city center was Marseille, France, in 1893, with its Noailles subterranean station (see Marseille tramway). It was initially operated by horse-drawn wagons. The next prominent example is Tremont Street Subway (1897) in Boston, today part of the MBTA Green Line. The concept of more systematic use of tunnels to carry tram lines under city centers was devised in Germany during the 1960s when, instead of building expensive entire metro systems immediately, the idea of building only the city centre tunnels at first was implemented. They could be used by trams in the short term, but the intention in the long run would still be the conversion to full underground-based rapid transit systems. The idea spread to other European countries in the 1970s, especially Belgium, where such systems were named premetros. Also portion of Vienna's U2 subway line (Rathaus-Museumsquartier) is a converted underground tramway line built in 1966.

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