In rail transportation, gauge conversion is the process of converting a railway from one rail gauge to another, through 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.

[edit] Rail vehicles

Gauge conversion of coaches and wagons involves the replacement of the wheelsets or entire bogies, such as happened when the 7 ft 0+¹⁄₄ in (2,140 mm) gauge of the Great Western Railway was abandoned in May 1892. Where vehicles regularly work to and fro across a permanent change of gauge, for example between the 4 ft 8+¹⁄₂ in (1,435 mm) system in France and the 1,668 mm (5 ft 5+²⁄₃ in) in Spain, stations are equipped with special bogie exchange equipment. Some vehicles nowadays are fitted with variable gauge axles which do not require any exchange of the wheelsets, but still require special equipment. This temporary alteration to allow through working is generally referred to as "gauge change".

Steam locomotives are difficult to convert unless this is already allowed for in the design, such as in some East African Railways Garratts, and in steam locomotives built for Victoria after 1930s. In the event, few have been so converted, but one such is Victorian Railways R class R766.

[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 1,000 mm (3 ft 3+³⁄₈ in)/1,067 mm (3 ft 6 in) and 1,435 mm (4 ft 8+¹⁄₂ in)/1,524 mm (5 ft) , dual gauge with a third rail is not practicable, in these cases 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 wider 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 Albury 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

During WWI and WWII, gauge conversion occurred backwards and forwards between Germany and Russia as the fronts and national borders changed.

• India conversion of 17,000 km of meter gauge to 1676 mm 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.
• 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 being made gauge convertible to facilitate an 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] Conversions to standard gauge

• 1941 Brest-Minsk^[1]
• 1970 Indian Pacific
• Spain is building its High Speed lines to 1,435 mm (4 ft 8+¹⁄₂ in) gauge, even though the existing system is 1,668 mm (5 ft 5+²⁄₃ in); new cutoff lines are being built with gauge convertible sleepers for easy conversion to standard gauge when required.
• May 2008 - agreement reached to standardise 200 km of 1,600 mm (5 ft 3 in) track carrying declining traffic from Seymour to Albury, making double track 1,435 mm (4 ft 8+¹⁄₂ in) route for increasing interstate traffic. The drought affected wheat-only 1,600 mm (5 ft 3 in) Oaklands branchline will be left as an orphan for time being. The cost of converting this 126 km line has been estimated as just over $13m. ^[2]
• Peru from Huancayo to Huancavelica from 914 mm (3 ft)  to 1,435 mm (4 ft 8+¹⁄₂ in); 147 km. ^[3]

[edit] Conversion rate

• 20 km/day for a battalion of 500-1500 men. ^[4]

[edit] See also

• Break-of-gauge
• Gauge conversion in the US
• Variable gauge
• Unigauge

[edit] References