Pre-metro

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 in a tunnel 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 was the Tremont Street Subway (1897) in Boston, today part of the MBTA Green Line.

The modern systematic use of a network of tunnels to carry streetcar or tramway lines was devised in Germany during the 1960s when, instead of building more expensive 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, hence the name "pre-metro". The idea spread to other European countries in the 1970s, especially Belgium, where such systems were explicitly officially named premetros.

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