Track gauge conversion is the changing of one railway

track gauge In rail transport, track gauge is the distance between the two rails of a railway track. All vehicles on a rail network must have Wheelset (rail transport), wheelsets that are compatible with the track gauge. Since many different track gauges ...

(the distance between the running rails) to another. In general, requirements depend on whether the conversion is from a wider gauge to a narrower gauge or vice versa, on how the rail vehicles can be modified to accommodate a track gauge conversion, and on whether the gauge conversion is manual or automated.

Sleepers

If tracks are converted to a narrower gauge, the existing timber sleepers (ties) may be used. However, replacement is required if the conversion is to a significantly wider gauge. Some sleepers may be long enough to accommodate the fittings of both existing and alternative gauges. Wooden sleepers are suitable for conversion because they can be drilled for the repositioned

rail spike A rail fastening system is a means of fixing Rail profile, rails to railroad ties (North America) or sleepers (British Isles, Australasia, and Africa). The terms ''rail anchors'', ''tie plates'', ''chairs'' and ''track fasteners'' are used to r ...

s. Concrete sleepers are unsuitable for conversion. Concrete sleepers may be cast with alternative gauge fittings in place, an example being those used during the conversion of the Melbourne–Adelaide railway from to . Steel sleepers may have alternative gauge fittings cast at production, may be drilled for new fittings or may be welded with new fittings.

Structures

Conversion from a narrow to a wider gauge may require enlargement of the

structure gauge A structure gauge, also called the minimum structure outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of s ...

of the bridges, overpasses and tunnels, embankments and cuts. The minimum curve radius may have a larger

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

on broader gauges requiring route deviations to allow the minimum curve radius to be increased. Track centers at

stations Station may refer to: Agriculture * Station (Australian agriculture), a large Australian landholding used for livestock production * Station (New Zealand agriculture), a large New Zealand farm used for grazing by sheep and cattle ** Cattle stat ...

with multiple tracks may also have to be increased. Conversion from narrow to standard gauge can cause several changes not because of the gauge itself, but in order to be compatible with the

of standard gauge track, such as height of overpasses so that trains can be exchanged. The choice of train couplers may be a factor as well.

Rail vehicles

Where vehicles move to a different gauge, they must either be prepared for

bogie exchange A bogie ( ) (or truck in North American English) comprises two or more wheelsets (two wheels on an axle), in a frame, attached under a vehicle by a pivot. Bogies take various forms in various modes of transport. A bogie may remain normally ...

or be prepared for wheelset exchange. For example,

passenger train A passenger train is a train used to transport people along a railroad line, as opposed to a freight train that carries goods. These trains may consist of unpowered passenger railroad cars (also known as coaches or carriages) push-pull train, ...

s moving between the in France and the gauge in Spain pass through an installation which adjusts their variable-gauge axles. This process is known as "gauge change".

Goods wagon Goods wagons or freight wagons (North America: freight cars), also known as goods carriages, goods trucks, freight carriages or freight trucks, are unpowered railway vehicles that are used for the transportation of cargo. A variety of wagon types ...

s are still subject to either bogie exchange or wheelset exchange.

Steam locomotives

Some

steam locomotives A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...

were constructed to be reconfigured to a different gauge: for example, some East African Railways locomotives;

Garratt A Garratt locomotive is a type of articulated steam locomotive invented by the engineer Herbert William Garratt that is articulated into three parts. Its boiler, firebox, and cab are mounted on a centre frame or "bridge". The two other ...

s; the large 500, 600 and 700 class locomotives of the

South Australian Railways South Australian Railways (SAR) was the organisation through which the Government of South Australia built and operated railways in South Australia from 1854 until March 1978, when its non-urban railways were incorporated into Australian Natio ...

introduced by William Webb in 1926; and the

Victorian Railways The Victorian Railways (VR), trading from 1974 as VicRail, was the state-owned operator of most rail transport in the Australian state of Victoria from 1859 to 1983. The first railways in Victoria were private companies, but when these companie ...

J, N and R classes. In the Australian instances, conversion was anticipated from broad gauge to standard gauge. Conversion to a wider gauge was similarly anticipated for the large narrow-gauge Western Australian Government Railways V class locomotive (to standard gauge). Of these locomotives, only one R class was converted (when in preservation). Two unanticipated conversions to occur were the ten locomotives of the South Australian Railways 740 class (from standard to broad gauge) and five narrow-gauge T class locomotives, which became the Tx class on the broad gauge before they were eventually converted back again. Gauge-change in steam locomotives has a long lineage. In about 1860, the

Bristol and Exeter Railway The Bristol and Exeter Railway (B&ER) was an English railway company formed to connect Bristol and Exeter. It was built on the broad gauge and its engineer was Isambard Kingdom Brunel. It opened in stages between 1841 and 1844. It was allied wi ...

converted five locomotives to gauge, and later converted them back again. Also in the 19th century, in the United States, some broad-gauge locomotives were designed for easy conversion to gauge, and in the United Kingdom some broad-gauge locomotive classes of the

Great Western Railway The Great Western Railway (GWR) was a History of rail transport in Great Britain, British railway company that linked London with the southwest, west and West Midlands (region), West Midlands of England and most of Wales. It was founded in 1833, ...

were designed for easy conversion to gauge. After

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, a number of captured German 03 class Pacifics locomotives were re-gauged to the

Russian gauge Russian(s) may refer to: *Russians (), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *A citizen of Russia *Russian language, the most widely spoken of the Slavic languages *''The Russians'', a b ...

Diesel and electric locomotives and trains

Most diesel and electric rolling stock can undergo gauge conversion by replacement of their bogies. Engines with fixed wheelbases are more difficult to convert. In Australia, diesel locomotives are regularly re-gauged between broad, standard and narrow gauges.

Wagons and coaches

Gauge conversion of wagons and coaches involves the replacement of the wheelsets or the

bogie A bogie ( ) (or truck in North American English) comprises two or more Wheelset (rail transport), wheelsets (two Railroad wheel, wheels on an axle), in a frame, attached under a vehicle by a pivot. Bogies take various forms in various modes ...

s. In May 1892, wagons and coaches were converted when the gauge of the

was abandoned.

Gauge orphan

During or after gauge conversion work, some stations and branch lines may become "gauge orphans". This occurs especially when it is not considered economically worthwhile to go to the expense of gauge conversion. For example, after the main line of the Adelaide–Wolseley railway line between Adelaide and Melbourne was converted in 1995 to standard gauge, the broad gauge Victor Harbor branch line became a gauge orphan because it was too lightly trafficked to be converted; it now prospers as a heritage line, SteamRanger.

References

Notes Citations

External links

{{DEFAULTSORT:Gauge Conversion Track gauges