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 wheelsets that are compatible with the track gauge. Since many different track gauges exist worldwide, gauge differences often present a barrier to wider operation on railway networks.
The term derives from the metal bar, or gauge, that is used to ensure the distance between the rails is correct.
Railways also deploy two other gauges to ensure compliance with a required standard. A loading gauge is a two-dimensional profile that encompasses a cross-section of the track, a rail vehicle and a maximum-sized load: all rail vehicles and their loads must be contained in the corresponding envelope. A structure gauge specifies the outline into which structures must not encroach.
Uses of the term
The most common use of the term "track gauge" refers to the transverse distance between the inside surfaces of the two load-bearing rails of a railway track, usually measured at to below the top of the rail head in order to clear worn corners and allow for rail heads having sloping sides. The term derives from the "gauge", a metal bar with a precisely positioned lug at each end that track crews use to ensure the actual distance between the rails lies within tolerances of a prescribed standard: on curves, for example, the spacing is wider than normal. Deriving from the name of the bar, the distance between these rails is also referred to as the track gauge.Choice of gauge
Early track gauges
The earliest form of railway was a wooden wagonway, along which single wagons were manhandled, almost always in or from a mine or quarry. Initially the wagons were guided by human muscle power; subsequently by various mechanical methods. Timber rails wore rapidly: later, flat cast-iron plates were provided to limit the wear. In some localities, the plates were made L-shaped, with the vertical part of the L guiding the wheels; this is generally referred to as a "plateway". Flanged wheels eventually became universal, and the spacing between the rails had to be compatible with that of the wagon wheels.As the guidance of the wagons was improved, short strings of wagons could be connected and pulled by teams of horses, and the track could be extended from the immediate vicinity of the mine or quarry, typically to a navigable waterway. The wagons were built to a consistent pattern and the track would be made to suit the needs of the horses and wagons: the gauge was more critical. The Penydarren Tramroad of 1802 in South Wales, a plateway, spaced these at over the outside of the upstands.
The Penydarren Tramroad probably carried the first journey by a locomotive, in 1804, and it was successful for the locomotive, but unsuccessful for the track: the plates were not strong enough to carry its weight. A considerable progressive step was made when cast iron edge rails were first employed; these had the major axis of the rail section configured vertically, giving a much stronger section to resist bending forces, and this was further improved when fish-belly rails were introduced.
Edge rails required a close match between rail spacing and the configuration of the wheelsets, and the importance of the gauge was reinforced. Railways were still seen as local concerns: there was no appreciation of a future connection to other lines, and the choice of track gauge was still a pragmatic decision based on local requirements and prejudices, and probably determined by existing local designs of vehicles.
Thus, the Monkland and Kirkintilloch Railway in the West of Scotland used ; the Dundee and Newtyle Railway in the north-east of Scotland adopted ; the Redruth and Chasewater Railway in Cornwall chose.
The Arbroath and Forfar Railway opened in 1838 with a gauge of, and the Ulster Railway of 1839 used.
"Standard" gauge appears
Locomotives were being developed in the first decades of the 19th century; they took various forms, but George Stephenson developed a successful locomotive on the Killingworth Wagonway, where he worked. His designs were successful, and when the Stockton and Darlington Railway was opened in 1825, it used his locomotives, with the same gauge as the Killingworth line,.The Stockton and Darlington line was very successful, and when the Liverpool and Manchester Railway, the first intercity line, was opened in 1830, it used the same gauge. It too was very successful, and the gauge, widened to and named "standard gauge", was well on its way to becoming the established norm.
Gauge differences
The Liverpool and Manchester was quickly followed by other trunk railways, with the Grand Junction Railway and the London and Birmingham Railway forming a huge preponderance of standard gauge. When Bristol promoters planned a line from London, they employed the innovative engineer Isambard Kingdom Brunel. He decided on a wider gauge, to give greater stability, and the Great Western Railway adopted a gauge of, later eased to. This became known as broad gauge. The Great Western Railway was successful and was greatly expanded, directly and through friendly associated companies, widening the scope of broad gauge.At the same time, other parts of Britain built railways to standard gauge, and British technology was exported to European countries and parts of North America, also using standard gauge. Britain polarised into two areas: those that used broad gauge and those that used standard gauge. In this context, standard gauge was referred to as "narrow gauge" to indicate the contrast. Some smaller concerns selected other non-standard gauges: the Eastern Counties Railway adopted. Most of them converted to standard gauge at an early date, but the GWR's broad gauge continued to grow.
The larger railway companies wished to expand geographically, and large areas were considered to be under their control. When a new independent line was proposed to open up an unconnected area, the gauge was crucial in determining the allegiance that the line would adopt: if it was broad gauge, it must be friendly to the Great Western railway; if narrow gauge, it must favour the other companies. The battle to persuade or coerce that choice became very intense, and became referred to as the "gauge wars".
As passenger and freight transport between the two areas became increasingly important, the difficulty of moving from one gauge to the other—the break-of-gauge—became more prominent and more objectionable. In 1845 a Royal Commission on Railway Gauges was created to look into the growing problem, and this led to the Regulating the Gauge of Railways Act 1846, which forbade the construction of broad gauge lines unconnected with the broad gauge network. The broad gauge network was eventually converted—a progressive process completed in 1892, called gauge conversion. The same Act mandated the gauge of for use in Ireland.
Gauge selection in other countries
As railways were built in other countries, the gauge selection was pragmatic: the track would have to fit the rolling stock. If locomotives were imported from elsewhere, especially in the early days, the track would be built to fit them. In some cases standard gauge was adopted, but many countries or companies chose a different gauge as their national gauge, either by governmental policy, or as a matter of individual choice.Terminology
Standard gauge is generally known world-wide as being. Terms such as broad gauge and narrow gauge do not have any fixed meaning beyond being materially wider or narrower than standard.In British practice, the space between the rails of a track is colloquially referred to as the "four-foot", and the space between two tracks the "six-foot", descriptions relating to the respective dimensions.
Standard gauge
In modern usage the term "standard gauge" refers to. Standard gauge is dominant in a majority of countries, including those in North America, most of western Europe, North Africa, the Middle East, and China.Broad gauge
In modern usage, the term "broad gauge" generally refers to track spaced significantly wider than.Broad gauge is the dominant gauge in countries in the Indian subcontinent, the former Soviet Union, Mongolia, Finland, Spain, Portugal, Argentina, Chile and Ireland. It is also used for the suburban railway systems in South Australia, and Victoria, Australia.
Medium gauge
The term "medium gauge" had different meanings throughout history, depending on the local dominant gauge in use.In 1840s, the Irish gauge was considered a medium gauge compared to Brunel's broad gauge and the narrow gauge, which became the modern standard gauge.
Narrow gauge
In modern usage, the term "narrow gauge" generally refers to track spaced significantly narrower than.Narrow gauge is the dominant or second dominant gauge in countries of Southern, Central, and East Africa; Southeast Asia; Japan; Taiwan; the Philippines; and Central and South America.
During the period known as the "battle of the gauges", Stephenson's standard gauge was commonly known as "narrow gauge", while Brunel's railway's gauge was termed "broad gauge". Many narrow gauge railways were built in mountainous regions such as Wales, the Rocky Mountains of North America, Central Europe and South America. Industrial railways and mine railways across the world are often narrow gauge. Sugar cane and banana plantations are mostly served by narrow gauges.
Minimum gauge
of under were used for some industrial railways in space-restricted environments such as mines or farms. The French company Decauville developed and tracks, mainly for mines; Heywood developed gauge for estate railways. The most common minimum gauges were,,,, or.Break of gauge
Through operation between railway networks with different gauges was originally impossible; goods had to be transshipped and passengers had to change trains. This was obviously a major obstacle to convenient transport, and in Great Britain, led to political intervention.On narrow gauge lines, rollbocks or transporter wagons are used: standard gauge wagons are carried on narrow gauge lines on these special vehicles, generally with rails of the wider gauge to enable those vehicles to roll on and off at transfer points.
On the Transmongolian Railway, Russia and Mongolia use while China uses the standard gauge of 1,435 mm. At the border, each carriage is lifted and its bogies are changed. The operation can take several hours for a whole train of many carriages.
Other examples include crossings into or out of the former Soviet Union: Ukraine/Slovakia border on the Bratislava–Lviv train, and the Romania/Moldova border on the Chișinău–Bucharest train.
A system developed by Talgo and Construcciones y Auxiliar de Ferrocarriles of Spain uses variable gauge wheelsets; at the border between France and Spain, through passenger trains are drawn slowly through an apparatus that alters the gauge of the wheels, which slide laterally on the axles.
A similar system is used between China and Central Asia, and between Poland and Ukraine, using the SUW 2000 and INTERGAUGE variable axle systems. China and Poland use standard gauge, while Central Asia and Ukraine use.