Premetro (or pre-metro) is a type of light rail designed for eventual conversion to a full rapid transit (also known as a metro). [1] [2] [3] These systems typically include infrastructure such as tunnels, viaducts, and dedicated rights-of-way to separate them from other traffic, built to metro standards with wider curves and gentler gradients than conventional light rail lines. [4] [5] [6] However, they often include sections without full segregation, limiting immediate conversion. Premetros are usually operated with light rail vehicles or trams until an upgrade is implemented.
Several cities have referred to portions of their light rail networks as a pre-metro, including Brussels [7] [8] and Antwerp. [9] [10] Additionally, Buenos Aires has a line light rail line named Premetro, [11] [12] however this operates as a feeder line to the metro network, and was not built with plans for conversion to full rapid transit. [13]
An early example of was the Tremont Street subway (1897) in Boston, today part of the MBTA Green Line. This tunnel was intended solely to reduce streetcar congestion on surface streets, not for later conversion to metro service. [14] However between 1901 and 1908, two out of four tracks were used for rapid transit service including high platforms. [15] Several early streetcar tunnels, including the Steinway Tunnel and East Boston Tunnel, were later converted to metro operation. However, the small loading gauge, tight curves, and steep grades of the streetcar tunnels required shorter metro cars than otherwise desirable. [14] In 1950 Stockholm converted a 1920s tram tunnel for its first rapid transit line. [16]
The modern premetro concept Stadtbahn began in 1960s Germany, as rising traffic congestion due to auto ownership led to the construction of new transit systems. Rather than building costly metro lines immediately, some cities built only the downtown tunnels. They could be used by existing tram lines in the short term, with the intention of full metro conversion later - hence "pre-metro". [17] The idea spread to other European countries in the 1970s, especially Belgium, where such systems were explicitly named premetros. [17] Also one segment of Vienna's U2 metro line (Rathaus-Museumsquartier) is an in 1980 converted underground tramway line, which was constructed in 1966.
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The use of tram vehicles in tunnels originated in the United States in the nineteenth century and was often called "subway–surface line". Later, in the second half of the twentieth century the term "semi-metro" was coined for tram systems with some sections in tunnels and on viaducts. Only when a semi-metro section is designed for later use of heavy rapid transit trains, it falls in the premetro category.[ citation needed ] The large scale report "Light Rail Transit: A State of the Art Review" describes on page 9 the relationship of premetro systems to broader terms as follows:
Certain design features distinguish these systems from semi-metro or conventional light rail transit systems [1]
The same distinction is made in glossaries. [3] [18] During the period when tram vehicles are used, the specific line falls into the light rail category. [19] [20]
This step-by-step planning approach to building rail rapid transit is known as pre-metro, implying the intention to ultimately construct a fully grade separated route to be used by rail rapid transit or metro trains.
pre-metro — a light rail transit system designed with provisions for easy conversion to heavy rail (rail rapid transit).
Premetros also allow a gradual upgrade of existing tramways to rapid transit, thus spreading the investments costs over time.
Cities such as Frankfurt and Cologne in West Germany have further developed their tramway system by introducing a concept known as "premetro." In this system trams or light rail vehicles make extensive use of tunnels, reserve track and by utilizing folding steps these vehicles can operate through high or low stopping places.
Pre-Metro is an extreme case of light rail, on segregated right of way, and designed to upgrading to metro when passenger demand increases sufficiently.
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has generic name (help)the outer tracks of the Tremont Street Tunnel which was adapted to elevated train use in 1901 by the construction of higher platforms
But instead of building the entire expensive systems immediately, the Germans hit on the idea of building only the city centre tunnels at first. Intended in the long run to be extended to full undergrounds, in the short term they could be used by trams which would continue to run on the surface outside city centres. The idea spread to other European countries, especially Belgium, where it became known as pre-metro. Today Brussels, Frankfurt, Stuttgart and many other cities are filling their central business districts with construction sites to move the trains underground.
Un semi-métro peut constituer une étape intermédiaire vers la constitution d'un véritable métro lorsqu'il est envisagé d'étendre par phases successives le site propre intégral à la totalité de la ligne ou du réseau. Les ouvrages sont alors dimensionnés au gabarit du futur métro et on parle du pré-métro.
pre-metro: a light rail transit system designed with provisions for easy conversion to rail rapid transit
PREMETRO—An LRT system designed with provisions for easy conversion into RRT (metro).
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: CS1 maint: location missing publisher (link)Antwerpen rail network is a typical premetro network.