Gauge conversion is the changing of one railway track gauge (the distance between the running rails) to another.

Sleepers

If tracks are converted to a narrower gauge, the existing sleepers (ties) may be used. However, replacement is required if the conversion is to a 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 spikes. Being difficult to drill, concrete sleepers are less suitable 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 of the bridges, overpasses and tunnels, embankments and cuts. The

minimum curve radius The minimum railway curve radius is the shortest allowable design radius for the centerline of railway tracks under a particular set of conditions. It has an important bearing on construction costs and operating costs and, in combination with ...

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

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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 structure gauge 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 or be prepared for wheelset exchange. For example,

passenger train A passenger train is a train used to transport people along a railroad line. These trains may consist of unpowered passenger railroad cars (also known as coaches or carriages) hauled by one or more locomotives, or may be self-propelled; self pr ...

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 wagons are still subject to either bogie exchange or

wheelset exchange Bogie exchange is a system for operating railway wagons on two or more gauges to overcome difference in the track gauge. To perform a bogie exchange, a car is converted from one gauge to another by removing the bogies or trucks (the chassis cont ...

Steam locomotives

Some steam locomotives were constructed to be reconfigured to a different gauge: for example, some

East African Railways The East African Railways and Harbours Corporation (EAR&H) is a defunct company that operated railways and harbours in East Africa from 1948 to 1977. It was formed in 1948 for the new East African High Commission by merging the Kenya and Ugand ...

locomotives;

Garratt A Garratt (often referred to as a Beyer Garratt) is a type of steam locomotive invented by British engineer Herbert William Garratt that is articulated into three parts. Its boiler, firebox, and cab are mounted on a centre frame or "bridge ...

s; the large

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, 600 and 700 class locomotives of the South Australian Railways introduced by William Webb in 1926; and the Victorian Railways 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 & 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 with ...

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. In the 20th century, in

Victoria station, London Victoria station, also known as London Victoria, is a central London railway terminus and connected London Underground station in Victoria, in the City of Westminster, managed by Network Rail. Named after the nearby Victoria Street (not the ...

, some broad-gauge locomotive classes of the

Great Western Railway The Great Western Railway (GWR) was a British railway company that linked London with the southwest, west and West Midlands of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament on 31 August 1835 and ran ...

were designed for easy conversion to gauge. After World War II, a number of captured German 03 class Pacifics locomotives were re-gauged to the Russian gauge.

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 ( ) (in some senses called a truck in North American English) is a chassis or framework that carries a wheelset, attached to a vehicle—a modular subassembly of wheels and axles. Bogies take various forms in various modes of transp ...

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, on the standard gauge

line Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...

between Adelaide and Melbourne, the broad gauge Victor Harbor branch line became a gauge orphan after the main line was converted in 1995 because it was too lightly trafficked; it now prospers as a heritage line, SteamRanger.

Notes

References

{{DEFAULTSORT:Gauge Conversion Track gauges