Gauge conversion
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| Rail gauge |
|---|
| Broad gauge |
| Standard gauge |
| Scotch gauge |
| Narrow gauge |
| Minimum gauge |
| List of rail gauges |
| Dual gauge |
| Gauge conversion |
| Break-of-gauge |
| Rail tracks |
| Tramway track |
| [edit] |
In rail transportation, gauge conversion is the process of converting a railway from one rail gauge to another, though the alteration of the railway tracks. An alternative to gauge conversion is dual gauge track, or gauge conversion of the rail vehicles themselves.
Ideally railways should all be built to the same gauge, since a wide range of gauges from narrow to broad are of similar value in carrying heavy loads at low cost, while small differences of gauge create tremendous break-of-gauge costs and inconvenience.
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[edit] Rail vehicles
Gauge conversion of rail vehicles initially involved the replacement of the wheelsets or bogies at gauge change stations that use special gauge change equipment, such as bogie exchange. However today, a more modern approach is variable gauge axles which do not require any exchange of the wheelsets, but still require special equipment.
[edit] Sleeper types
Often gauge convertible sleepers are installed before the conversion of the rails themselves. Sleepers have to be long enough to take the wider of the gauges, and secondly, the sleepers must be able to take the fittings of both gauges that allow the rails to be fixed securely to those sleepers. Gauge convertibility can also be a stepping stone to dual gauge. In cases where the differences between the gauges are small, such as 1000 mm/1067 mm and 1435 mm/1524 mm, dual gauge with a third rail may not be practicable, in which case four rail dual gauge is necessary.
- Timber sleepers, provided that they are long enough, are always gauge convertible, since additional holes for the dogspikes can always be drilled later. If the new gauge is longer than the old, a shorter than normal sleeper can be tolerated to a degree.
- Concrete sleepers cannot be converted as an afterthought, but must have the future fittings cast in place at the manufacturing stage.
- Steel sleepers should have the extra fitting incorporated at the initial manufacturing stage, though it might be possible to drill or weld the fitted sleeper after installation albeit with some difficulty.
[edit] Gauge Orphan
During gauge conversion work such as between Seymour and Aubury branch lines such as Benalla to Oaklands and stations such as Violet Town become gauge orphans as they cannot easily be served by trains until extra costly work is done.
[edit] Examples
India conversion of 17,000 km of meter gauge to broad gauge under project Unigauge
Melbourne to Adelaide - 600 km of convertible sleepers installed in 1990 to facilitate quick conversion in 1995.- Adelaide - convertible sleepers installed should gauge conversion be needed in future.
Port Harcourt - Onne, Nigeria - convertible sleepers installed since gauge conversion not imminent.- The Mt Gambier line in South Australia was fitted with some 3-gauge steel sleepers when it was "temporarily" converted from 1067 mm to 1600 mm in the 1950s, pending later conversion to 1435 mm from 2008.
Spain is building its High Speed lines to 1435 mm gauge, even though the existing system is 1668 mm; new cutoff lines are being built with gauge convertible sleepers for easy conversion to standard gauge when required.- Central Asia - while
China and 
Europe are connected by rail, and while both are mainly 1435 mm, the intervening Central Asia Railways are 1520 mm gauge. Intervening lines are gradually been made gauge convertible to facilitate and eventual linkage of the Chinese and European standard gauge system. 
Tanzania in 2008 is proposing 1000 mm/1067 mm steel sleepers and 1000 mm/1435 mm concrete sleepers to suit gauge conversion.
[edit] 2008
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May 2008 - agreement reached to standardise 200km of 1600mm track carrying declining traffic from Seymour to Albury, making double track 1435mm route for increasing interstate traffic. The drought affected wheat-only 1600mm Oaklands branchline will be left as an orphan for time being.
