| Part of a series on |
| Rail transport |
|---|
 |
| Infrastructure |
| Rolling stock |
| Urban rail transit |
| Topics |
 Transport portal |
Tramway track is used ontramways orlight rail operations. As with standardrail tracks, tram tracks have twoparallel steel rails, the distance between the heads of the rails being thetrack gauge. When there is no need for pedestrians or road vehicles to traverse the track, conventionalflat-bottom rail is used. However, when such traffic exists, such as in urban streets,grooved rails are used.
Tram rails can be placed on several surfaces, such as on ground over whichtrack ballast topped bysleepers (US: ties) andflat-bottom rails are laid – as with railway tracks – or, forstreet running, with grooved rails usually embedded into aconcretepavement. In some places, tracks are laid intograss turf surfaces; they are known asgreen track,grassed track ortrack inlawn.
Tramway tracks have been in existence since the mid-16th century. They were made of wood, but during the late 18th century iron and later steel came into use and then predominated.
The first street tramways were laid in 1832 in New York byJohn Stephenson to assist horses pulling buses ondirt roads, especially when the roads were muddy from wet weather. The rails enabled a horse to easily pull a load of 10 tonnes compared to 1 tonne on a dirt road. The evolution of street tramway tracks paralleled the transition from horse power to mechanical and electric power. In a dirt road, the rails needed a foundation, usually a mass concrete raft. Highway authorities often made tramway companies pave the rest of the road, usually with granite or similar stone blocks, at extra cost.
The first tramways had a rail projecting above the road surface, or a step set into the road, both of which were apt to catch the narrow tyres of horse-drawn carriages. The invention byAlphonse Loubat in 1852 of grooved rail enabled tramways to be laid without causing a nuisance to other road users, except unsuspectingcyclists, who could get their wheels caught in the groove.
Agrooved rail,groove rail, orgirder rail is aspecial rail with agroove designed for tramway or railway track inpavement or grassed surfaces (grassed track or track in a lawn). The head on the right-hand side of the rail bears the vehicle's weight. The guard on the left-hand side, which has ample room for wheel flanges, carries no weight but serves to minimize the chance of derailment if the wheel were to be deflected from its normal position in which the flange is not laterally constrained.
Grooved rail was invented in 1852 byAlphonse Loubat, a French inventor who developed improvements intram and rail equipment and helped develop tram lines in New York City and Paris. The invention of grooved rail enabled tramways to be laid without causing a nuisance to other road users, except unsuspecting cyclists, who could get their wheels caught in the groove. The grooves may become filled with gravel and dirt (particularly if infrequently used or after a period of idleness) and need clearing from time to time, this being done by a "scrubber" tram. Failure to clear the grooves can lead to a bumpy ride for the passengers, damage to either wheel or rail and possibly derailing.
The traditional form of grooved rail is the girder guard section illustrated below. This rail is a modified form of flanged rail and requires a special mounting for weight transfer and gauge stabilisation. If the weight is carried by the roadway subsurface, steel ties are needed at regular intervals to maintain the gauge. Installing these means that the whole surface needs to be excavated and reinstated.
Block rail is a lower profile form of girder guard rail, where the web is eliminated. In profile it is more like a solid form of bridge rail with a flangeway and guard added. Simply removing the web and combining the head section directly with the foot section would result in a weak rail, so additional thickness is required in the combined section.[1]
A modern version of the grooved block rail has a lower mass and is inserted into a prefabricated spanning concrete girder such as the LR55[2] without web but fully supported by noise reducing polyurethane grout or a girder rail such as P-CAT City Metro[3] is embedded. The prefabricated units if used with ultra light trams can be embedded into existing road base with possibly a reduced requirement for underground services diversions.
Electrification needed other developments, most notably heavier rails to cope with electric tramcars weighing 12 tonnes rather than the 4 tonne horse-drawn variety; switching points, as electric trams could not be pulled onto the correct track by horses; and the need for electrical connections, to provide the return path for the electric current, which was usually supplied through anoverhead wire.
In some cities where overhead electric cables were deemed intrusive, undergroundconduits with electrical conductors were used. Examples of this were New York, Washington DC, Paris, London, Brussels and Budapest. The conduit system of electrical power was very expensive to install and maintain, although Washington did not close until 1962. Attempts were made with alternative systems not needing overhead wires. There were many systems of “surface” contact, wherestuds were set in the road surface, and energised by a passing tram, either mechanically or magnetically, to supply power through a skate carried under the tram. Unfortunately these systems all failed due to the problem of reliability and not always turning off after the tram had passed, resulting in the occasional electrocution of horses and dogs.[citation needed] Since 2003, a new system ofsurface contact has been installed in theBordeaux tramway by Alstom.
Prior to the universal introduction of electric power, many tramways werecable hauled, with a continuous cable carried in a conduit under the road, and with a slot in the road surface through which the tram could clasp the cable for motion. Thissystem can still be seen inSan Francisco in California as well as thesystem of theGreat Orme in Wales. These needed a rather more substantial track formation.
.jpg)
_light_rail_station.jpg)
Media related toTram tracks at Wikimedia Commons
