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A narrow gauge railway (or narrow gauge railroad) is a railway that has a track gauge narrower than the 1,435 mm (4 ft 8 1⁄2 in) of standard gauge railways. Most existing narrow gauge railways have gauges of between 600 mm (1 ft 11 5⁄8 in) and 3 ft 6 in (1,067 mm).
Since narrow gauge railways are usually built with smaller radius curves, smaller structure gauges, lighter rails, etc., they can be substantially cheaper to build, equip, and operate than standard gauge or broad gauge railways, particularly in mountainous or difficult terrain. The lower costs of narrow gauge railways mean they are often built to serve industries and communities where the traffic potential would not justify the cost of building a standard or broad gauge line.
Narrow gauge railways also have more general applications. Non-industrial narrow gauge mountain railways are or were common in the Rocky Mountains of the United States and the Pacific Cordillera of Canada, in Mexico, Switzerland, the former Yugoslavia, Greece, India, and Costa Rica.
The earliest recorded railway is shown in the De re metallica of 1556, which shows a mine in Bohemia with a railway of approximately 2 ft (610 mm) gauge. During the 16th century railways were mainly restricted to hand-pushed narrow gauge lines in mines throughout Europe. During the 17th century mine railways were extended to provide transportation above ground. These lines were industrial, connecting mines with nearby transportation points, usually canals or other waterways. These railways were usually built to the same narrow gauge as the mine railways from which they developed.
The world's first steam locomotive on rails, built in 1802 by Richard Trevithick for the Coalbrookdale Company, ran on a 3 ft (914 mm) plateway. During the 1820s and 1830s, a number of industrial narrow gauge railways in the United Kingdom used steam locomotives. In 1842 the first narrow gauge steam locomotive outside the UK was built for the 1,100 mm (3 ft 7 7⁄16 in) gauge Antwerp-Ghent Railway in Belgium. The first use of steam locomotives on a public, passenger carrying narrow gauge railway came in 1865 when the Ffestiniog Railway introduced its passenger service, after receiving its first locomotives two years prior.
Historically, many narrow gauge railways were built as part of specific industrial enterprises and were primarily industrial railways rather than general carriers. Some common uses for these industrial narrow gauge railways were mining, logging, construction, tunnelling, quarrying, and the conveying of agricultural products. Extensive narrow gauge networks were constructed in many parts of the world for these purposes.
For example, mountain logging operations in the 19th century often used narrow gauge railways to transport logs from mill sites to market. Significant sugarcane railways still operate in Cuba, Fiji, Java, the Philippines and in Queensland in Australia. Narrow gauge railway equipment remains in common use for the construction of tunnels.
Extensive narrow gauge railway systems served the front-line trenches of both sides in World War I. They were a short-lived military application, and after the end of the war the surplus equipment from these created a small boom in narrow gauge railway building in Europe.
Narrow gauge railways usually cost less to build because they are usually lighter in construction, using smaller cars and locomotives (smaller loading gauge) as well as smaller bridges, smaller tunnels (smaller structure gauge) and tighter curves. Narrow gauge is thus often used in mountainous terrain, where the savings in civil engineering work can be substantial. It is also used in sparsely populated areas where the potential demand is too low for broader gauge railways to be economically viable. This is the case in some of Australia and most of Southern Africa, where extremely poor soils have led to population densities too low for standard gauge to be viable.
For temporary railways that will be removed after short term use, such as for construction, the logging industry, the mining industry or large scale construction projects, especially in confined spaces, such as the Channel Tunnel, a narrow gauge railway is substantially cheaper and easier to install and remove. The use of such railways has almost vanished due to the capabilities of modern trucks.
In many countries, narrow gauge railways were built as "feeder" or "branch" lines to feed traffic to more important standard gauge lines, due to their lower construction costs. The choice was often not between a narrow gauge railway and a standard gauge one, but between a narrow gauge railway and none at all.
Narrow gauge railways cannot interchange rolling stock such as freight and passenger cars freely with the standard gauge or broad gauge railways they link with, the transfers of passengers and freight require time consuming manual labour or substantial capital expenditure. Some bulk commodities, such as coal, ore and gravel, can be mechanically transshipped, but this still incurs time penalties and the equipment required for the transfer is often complex to maintain.
Also in times of peak demand, it is very difficult to move rolling stock to wherever they are needed when there is a break of gauge. So there had to be enough rolling stock to meet a narrow gauge railways own peak demand, which might be much more than needed by equivalent standard gauge railways, and the surplus equipment generated no cash flow during periods of low demand.
Solutions to these problems of transshipment is bogie exchange between cars, a rollbock system, variable gauge, dual gauge, or even gauge conversion. European standard gauge trains normally use buffers and chain couplers, which do not allow so tight curves, a main reason to have narrow gauge. Therefore narrow gauge trains normally use other couplers, which makes bogie exchange meaningless.
Another problem for narrow gauge railways was that they lacked the physical space to grow: their cheap construction meant they were engineered only for their initial traffic demands. While a standard or broad gauge railway could more easily be upgraded to handle heavier, faster traffic, many narrow gauge railways were impractical to improve. Speeds and loads hauled could not increase, so traffic density was significantly limited.
Narrow gauge railways can be built to handle increased speed and loading, but at the price of removing most of the narrow gauge's cost advantage over standard or broad gauge.
The heavy duty 3 ft 6 in (1,067 mm) narrow gauge railways in Australia (e.g. Queensland), South Africa and New Zealand show that if the track is built to a heavy-duty standard, performance almost as good as a standard gauge line is possible. 200-car trains operate on the Sishen-Saldanha railway in South Africa, and high-speed tilt-trains in Queensland (see below). Another example of a heavy-duty narrow gauge line is EFVM in Brazil. 1,000 mm (3 ft 3 3⁄8 in) gauge, it has over-100-pound rail (100 lb/yd or 49.6 kg/m) and a loading gauge almost as large as US non-excess-height lines. It sees multiple 4,000 hp (3,000 kW) locomotives and 200+ car trains. In South Africa and New Zealand, the loading gauge is similar to the restricted British loading gauge, and in New Zealand some British Rail Mark 2 carriages have been rebuilt with new bogies for use by Tranz Scenic (Wellington-Palmerston North service), Tranz Metro (Wellington-Masterton service) and Veolia (Auckland suburban services).
The reduced stability of narrow gauge means that its trains cannot run at the same high speeds as on broader gauges, unless the tracks are aligned with greater precision. In Japan and in Queensland, Australia, recent permanent way improvements have allowed trains on 1,067 mm (3 ft 6 in) gauge tracks to run at 160 km/h (99 mph) and faster. Queensland Rail's tilt train is currently the fastest train in Australia and the fastest 1,067 mm (3 ft 6 in) gauge train in the world, setting a record at 210 km/h. A special 2 ft (610 mm) gauge railcar was built for the Otavi Mining and Railway Company with a design speed of 137 km/h.
Compare these speeds with standard gauge or broad gauge trains which can run at up to 320 km/h (199 mph). The contrast is most evident in Japan, home of the Shinkansen, a network of standard gauge lines built solely for high speed rail in a country where 1,067 mm (3 ft 6 in) narrow gauge is the predominant standard.
Curve radius is also important for high speeds: narrow gauge railways tend to have sharper curves, which limits the speed at which a vehicle can safely proceed along the track.
Many engineers considered the cost of a railway varies with some power of the gauge, so that the narrower gauge the cheaper it might be. This applied also to different narrow gauges, such as a proposed line in Papua using either 610 mm (2 ft) or 1,067 mm (3 ft 6 in).
In general, a narrow gauge railway has a track gauge less than 1,435 mm (4 ft 8 1⁄2 in) gauge. However, due to historical and local circumstances the definition of a narrow gauge railway can be different.
There are many narrow gauges in use or formerly used between 15 in (381 mm) gauge and 4 ft 8 1⁄2 in (1,435 mm) gauge. They fall into several broad categories:
Scotch gauge was the name given to a 4 ft 6 in (1,372 mm) track gauge, that was adopted by early 19th century railways mainly in the Lanarkshire area of Scotland. Also 4 ft 6 1⁄2 in (1,384 mm) lines were constructed. Both gauges were eventually converted to standard gauge.
1,067 mm (3 ft 6 in) between the inside of the rail heads. The name and classification varies throughout the world. It has installations of around 112,000 kilometres (70,000 mi).
Similar gauges are:
As a result of Italian law track gauges in Italy were defined from the centres of each rail, rather than the inside edges of the rails. This gauge was measured 950 mm (3 ft 1 3⁄8 in) between the edges of the rails and is known as Italian metre gauge
900 mm (2 ft 11 7⁄16 in) gauge railways are generally found in Europe.
Swedish three foot gauge railways (891 mm (2 ft 11 3⁄32 in)) can only be found in Sweden.
These lightweight lines can be built at a substantial cost saving over medium or standard gauge railways, but are generally restricted in their carrying capacity. The majority of these lines were built in mountainous areas, the majority for carrying mineral traffic from mines to ports or standard gauge railways.
Gauges: 2 ft (610 mm), 1 ft 11 3⁄4 in (603 mm), 600 mm (1 ft 11 5⁄8 in), and 1 ft 11 1⁄2 in (597 mm)
Gauges below 1 ft 11 1⁄2 in (597 mm) were rare, but did exist. In Britain, Sir Arthur Heywood developed 15 in (381 mm) gauge estate railways, while in France Decauville produced a range of industrial railways running on 500 mm (19 3⁄4 in) and 400 mm (15 3⁄4 in) tracks, most commonly in restricted environments such as underground mine railways, parks and farms. Several 18 in (457 mm) gauge railways were built in Britain to serve ammunition depots and other military facilities, particularly during World War I.