Ballastless track
Discretely supported rails sit on elastomeric pads and are rigidly fastened to special types of concrete sleepers.
[3] Special care is needed for the design of transitions zones between conventional and ballastless track, for example near bridges.
[8][9] Due to its good experiences with the system, the Swiss Federal Railways are looking to install ballastless track wherever there is a rigid substructure—in tunnels as well as on viaducts.
Further advantages of ballastless tracks include better and controlled drainage, the elimination of flying-ballast damage on rolling stock and civil engineering structures, a shallower superstructure, and the possibility of run-over sections such as crossings or shared tram-bus lanes over which pneumatic vehicles can be driven.
[9][2] Embedded track has the potential for increased safety through simple derailment protection and support of broken rails.
[11] Further disadvantages of ballastless tracks are the difficulty of adjusting or correcting track geometry once concrete has been set, the necessity of a stable infrastructure (since adjustments to the superstructure can be onerous), generally higher noise emissions, and longer and more expensive repairs when the concrete slab is damaged (for e.g., due to construction faults, wear and tear, or accidents).
[12][13] Early slab track projects a range of construction types, sub-bases and fastening technologies.
[14] The following list contains construction types of ballastless tracks that have been internationally used in heavy-rail systems (as opposed to light railways, tramways, or metros) in chronological order of their first usage.
[18][19] The Bözberg/STEDEF system consists of twin sleepers that are connected by a steel track rod and enclosed in a rubber shoe.
[20] The Bögl ballastless track is characterised by its use of prefabricated concrete slabs in lieu of a continuous structure that is cast on site.
It was first tested in 1989, became the standard system in Austria in 1995,[22] and has been used for over 700 kilometres of track worldwide, including the German Verkehrsprojekt Deutsche Einheit Nr.
[24] The Low Vibration Track (LVT) system is similar to Bözberg/STEDEF in that it also uses twin sleepers enclosed in rubber shoes.
[9] The system was developed and tested by Roger Sonneville together with the Swiss Federal Railways in the 1990s[3] before the rights were sold to Vigier Rail in 2009.
LVT has been used for over 1300 kilometres of track worldwide, including the Swiss Lötschberg, Gotthard and Ceneri base tunnels, the South Korean high-speed Suin Line between Songdo and Incheon, the Turkish Marmaray project, and the London Overground's East London line, as well as on viaducts in urban areas.
Due to the large diameter of the hollow beam and its light weight, it is particularly suitable for low profile designs on soft soils.
