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Typically light-rail systems are urban, use short and light trains, and can handle steeper gradients and sharper curves than heavy rail. They may run along roads like trams.
They are generally powered by electricity, sometimes not by overhead wires, but by a live rail, also called third rail (a high voltage bar alongside the track), requiring safety measures and warnings to the public not to touch it.
Some systems are automatic, dispensing with the need for a driver.
Terminology is not quite fixed: 'light rail' can be used as a category between tram and heavy rail, but a modern tram system may also be called light rail.
Light-rail systems are generally cheaper to build than heavy rail, since the infrastructure does not need to be as substantial. Moreover, the ability to handle sharp curves and steep gradients can reduce the scale of building work required.
Many light-rail projects re-use parts of old rail networks, such as abandoned industrial lines.
A good example of both points above is the Docklands Light Railway in London, which uses a sharp, steep, curve to enable it to transfer from running alongside an existing railway line to a disused railway line which crossed underneath the first line. A direct connection between these lines would not be practical for conventional rail.
Around Karlsruhe and Saarbrücken, Germany, light rail vehicles partly use heavy rail tracks, sharing these tracks with heavy rail trains. In the Netherlands this will first be applied on the RijnGouweLijn, to be constructed.
Some of the issues involved are:
- compatibility of the safety systems
- power supply of the track in relation to the power used by the vehicles (voltage, and third rail vs. overhead wires)
- width of the vehicles in relation to the position of the platforms
- height of the platforms
"Light-rail" should have a hyphen when used as an attributive adjective.
See also
External links
- http://www.rinbad.demon.co.uk/ca_rail.htm
- http://www.ntdprogram.com/NTD/NTDData.nsf/2000+TOC/Table20/File/t20_32.html
- Table of Light Rail Transit Agencies in the United States (http://www.apta.com/stats/modesumm/lragency.htm)