Rail gauge is the distance between the inner sides of the two parallel rails that make up a railway track. Sixty percent of the world's railways use a gauge of , which is known as the standard or international gauge. Gauges wider than standard gauge are called broad gauge, those smaller are called narrow gauge. The term break-of-gauge refers to the situation at a place where different gauges meet. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to share the same path. Gauge conversion can be used to reduce break-of-gauge situations.
|Indian gauge||India (Project Unigauge - 42,000 km), Pakistan, Argentina, Chile|
|Iberian gauge||14,337.2 km (2007) + 21 km mixed gauge in Spain (Iberian+UIC, three rails on the same sleeper)||Portugal, Spain|
|Irish gauge||9,800 km||Ireland and important minor gauge in Australia - Victorian gauge (4,017 km), Brazil (4,057 km)|
|Russian gauge||7,000 km||Finland, Estonia|
|Russian gauge||220,000 km||CIS states, Latvia, Lithuania, Mongolia|
|Standard gauge||720,000 km||Europe, North America, China, Australia, Middle East (60% of the world's railways)|
|Cape gauge||112,000 km||Southern and Central Africa, Indonesia, Japan, Taiwan, Philippines, New Zealand|
|Metre gauge||95,000 km||SE Asia, India (17,000 km, some under gauge conversion with Project Unigauge to Indian gauge, Brazil (23,489 km)|
For details see: List of rail gauges
Note: Russian gauge can refer to 1524 mm or to 1520 mm.
The designers of both chariots and trams and trains were dealing with a similar issue, namely hauling wheeled vehicles behind draft animals. A more likely theory as to why the measurement was chosen is that it reflects vehicles with a "outside" gauge.
Italy defined its gauges from the centres of each rail , rather than the inside edges of the rails, giving some unusual measurements (950 mm instead of 1000 mm). According to the law of 28.VII.1879, the only legal gauge widths in Italy were 1500, 1000 and 750 measured on the middle of the rail, corresponding to 1445, 950, and 700 mm inside the rail.
The standard gauge of was chosen for the first main-line railway, the Liverpool and Manchester Railway (L&MR), by the British engineer George Stephenson; however, the de facto standard for the colliery railways where Stephenson had worked was 4 ft 8 in. Whatever the origin of the gauge it seemed to be a satisfactory choice: not too narrow and not too wide.
Brunel on the Great Western Railway chose the broader gauge of partly because it offered greater stability and capacity at high speed, but also because the Stephenson gauge was not scientifically selected. The Eastern Counties Railway chose five-foot gauge, but soon realised that lack of compatibility was a mistake and changed to Stephenson's gauge. The conflict between Brunel and Stephenson is often referred to as the Gauge War.
In 1845 a United Kingdom of Great Britain and Ireland Royal Commission recommended adoption of as standard gauge in Great Britain; and in Ireland a standard gauge of 5 ft 3 in (1,600 mm). The following year the Parliament of the United Kingdom passed the Gauge Act, which required that new railways use the standard gauge. Except for the Great Western Railway's broad gauge, few main-line railways in Great Britain used a different gauge. The last Great Western line was finally converted to standard gauge in 1892.
Broad gauge is a blanket term that refers to any gauge wider than standard gauge, or . Russian, Indian, Irish, and Iberian gauges can all be referred to as broad gauge. Broad gauge railroads are also common in docks for short distances. Broad gauge is used to provide better stability and axle load or, in some cases, to prevent the easy transfer of rolling stock from railroads of other countries for political or military reasons. Compare with Narrow Gauge.
Russian gauge is in width and is the second most widely used gauge in the world.
Engineer Pavel Melnikov hired George Washington Whistler, a prominent American railroad engineer (and father of the artist James McNeill Whistler), to be a consultant on the building of Russia's first major railroad, the Moscow–Saint Petersburg line. The selection of gauge was recommended by German and Austrian engineers but not adopted: it was not the same as the gauge in common use in the southern United States at the time. Russian gauge was originally defined as on September 12 1842 and standardised to the present in the late 1960s.
The unconnected system on Sakhalin Island, in the far east of Russia, has retained the previous Japanese standard gauge, as originally built. In 2004 a project was presented to convert this system to match Russian gauge.
Since the beginning of the 1990s new high-speed passenger lines in Spain have been built to the international standard gauge of , to allow these lines to link to the European high-speed network. Although the 22 km from Tardienta to Huesca (part of a branch from the Madrid to Barcelona high-speed line) has been reconstructed as mixed Iberic and standard gauge, in general the interface between the two gauges in Spain is dealt with by means of gauge-changing installations, which can adjust the gauge of appropriately designed wheelsets on the move .
There are plans to convert the whole broad gauge network to standard gauge, but so far the only visible indication is the use of dual gauge concrete sleepers (with two positions of bolt holes) on stretches of relaid broad-gauge track.
The track gauge adopted by the mainline railways in Ireland is . This unusual gauge is otherwise found only in the Australian states of Victoria, southern New South Wales (as part of the Victorian rail network) and South Australia (where it was introduced by the Irish railway engineer F. W. Shields), and in Brazil.
The first three railways all had different gauges: the Dublin and Kingstown Railway, ; the Ulster Railway, ; and the Dublin and Drogheda Railway, . The Board of Trade, recognising the chaos that would ensue, asked one of their officers to advise. After consulting widely he eliminated both the widest and narrowest gauges (Brunel's and Stephenson's ), leaving gauges between and . By a typically Irish approach to splitting the difference, a compromise Irish gauge of in was adopted.
In the 19th century, Australia's three mainland states adopted standard gauge, but due to political differences, a break of gauge 30 years in the future was created. After instigating a change to agreed to by all, New South Wales reverted to standard gauge while Victoria and South Australia stayed with broad gauge. Three different gauges are currently in wide use in Australia, and there is little prospect of full standardisation, though the main interstate routes are now standard gauge.
The most widely used narrow gauges are
There are also minimum gauge railways.
When a railway line of one gauge meets another railway line of a different gauge, there is a break of gauge. A break of gauge adds cost and inconvenience to traffic that must pass from one system to another.
An example of this is on the Transmanchurian Railway, where Russia and Mongolia use broad gauge while China uses the standard gauge. At the border, each carriage has to be lifted in turn to have its bogies changed. The whole operation, combined with passport and customs control, can take several hours.
Other examples include any crossing into or out of the former Soviet Union: Ukraine/Slovakia border on the Bratislava-L'viv train, and from the Romania/Moldova border on the Chisinau-Bucharest train.
This can be avoided however by implementing a system similar to that used in Australia, where lines between states using different gauges are built as dual gauge. Thus the lines have 3 rails, one set of two forming a standard gauge line, with the third rail either inside or outside the standard set forming rails at either narrow or broad gauge. As a result, trains built to either gauge can use the line.
|and gauges are too close to allow three-rail dual gauge.||and gauges can be used together, with four-rail dual gauge - note the third (useless) 1,267 mm gauge.||and gauges can be used together with four-rail dual gauge, with bonus 1435mm standard gauge.|
Africa is particularly affected by gauge problems, where railways of different gauges in adjacent countries meet.
Gauge rationalisation in Africa is facilitated since four-rail dual gauge of and contains a hidden gauge, which can be made to be standard gauge . The four-rail system reuses and doubles the effective strength of the old light rails, which might otherwise have only a low value reuse as fenceposts.
The United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP) is planning a Trans-Asian Railway that will link Europe and the Pacific, with a Northern Corridor from Europe to the Korean Peninsula, a Southern Corridor from Europe to Southeast Asia, and a North-South corridor from Northern Europe to the Persian Gulf. All the proposed corridors would encounter one or more breaks of gauge as they cross Asia. Current plans do not call for widespread gauge conversion; instead, mechanized facilities would be built to move shipping containers from train to train at the breaks of gauge.