Semi-metro (also known as a subway–surface[1][2][3][4][5] line or a hybrid[6] streetcar / light rail line) is a form of public rail transport in which trams run partly on a conflict-free track,[7][8] by using tunnels and viaducts.[9][10] These stretches of track are designed to function like a regular metro or rapid transit line.[11][12] Semi-metro lines run with tram cars because they are usually developed from an existing tram network.[13][14]
One key difference from metro lines (rapid transit) is that semi-metro lines only partially run in tunnels and on viaducts.[15] A metro line has an entirely conflict-free track, often completely grade separated. Semi-metro routes are operated by regular trams (with or without low floor) or with specially developed tramcars (light rail vehicles), such as the Stadtbahn-car 'type B'.[16]: 55
By this time, there was considerable interest in reconfiguring the U.S. subway-surface streetcar systems to resemble northern European practice, and there was increasing recognition that modern tramways might be appropriate for urban regions that long since had given up streetcar operation.
light rail subway/surface line
Do lekkiej kolei zaliczymy także systemy pośrednie między metrem a tramwajem. Bezkolizyjność trasy oraz kolejowy system sterowania w połączeniu z taborem tramwajowym to semi-metro. System taki może działać jako semi-metro w obszarze śródmiejskim, a w dzielnicach zewnętrznych jako szybki tramwaj. — Light rail also includes intermediate systems between the metro and the tram. The collision-free route and the railway control system combined with the tram rolling stock are called semi-metro. Such a system can operate as a semi-metro in the city center, and in the outer districts as a rapid tram.
descending into tunnels in the style of conventional underground mass transit
Semi-metro: Light rail on reserved right of way over congested parts of line typically in tunnel or viaduct for grade separation designed to Metro standards, with priority surface light rail in other sections
In essence, a semi-metro consists of light rail cars operating on exclusive tracks, generally on the surface but descending into tunnels in the style of conventional underground mass transit in city centres
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