A narrow-gauge railway (or narrow-gauge railroad in the US) is a railway with a track gauge narrower than the 1,435 mm (4 ft 8 1⁄2 in) standard-gauge railways. Most existing narrow-gauge railways are between 600 mm (1 ft 11 5⁄8 in) and 1,067 mm (3 ft 6 in).
Since narrow-gauge railways are usually built with smaller radius curves, smaller structure gauges, lighter rails, etc., they can be substantially less costly 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 specialized use in mines and other environments where a very small structure gauge makes a very small loading gauge necessary. 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, and Costa Rica. In some countries, narrow gauge is the standard, like the 3 ft 6 in (1,067 mm) gauge in Japan, Indonesia, Taiwan, New Zealand, South Africa, the Australian states of Queensland, Western Australia and Tasmania, and the 1,000 mm (3 ft 3 3⁄8 in) metre gauge in Malaysia and Thailand.
In general, a narrow-gauge railway has a track gauge less than standard gauge. However, due to historical and local circumstances, the definition of a narrow-gauge railway can be different.
The earliest recorded railway is shown in the De re metallica of 1556, which shows a mine in Bohemia with a railway of about 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 5⁄16 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 Queensland. 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 with which they link, and 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.
If rail lines with other gauges coexist in the network, in times of peak demand, it is very difficult to move rolling stock to where it is needed when a break of gauge exists, so enough rolling stock must be available to meet a narrow-gauge railways' own peak demand, which might be much more than needed when compared to a network with only one gauge, and the surplus equipment generates no cash flow during periods of low demand. In regions where narrow gauge forms only a small part of the rail network, like the Sakhalin railway in Soviet Russia, extra cost is needed to specifically design, produce or import narrow-gauge equipment which increases the cost of narrow-gauge vehicle compared to regular vehicles.
Another problem commonly faced by narrow-gauge railways was that they lack 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 can be 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. In the case of Queensland, Australia, the Queensland Rail passenger network has nearly reached its capacity due to the narrow gauge and an ever-increasing population, as such, new lines are to be built, thus negating the original cost savings. In Japan, a few narrow gauge lines have been upgraded to standard gauge mini-shinkansen to allow through service by standard gauge high-speed vehicles, but due to the alignment of those lines and minimum curve radius of those lines, the maximum speed of those through service is still the same as the original narrow-gauge rail line.
If a narrow-gauge line is built to higher standard like the proposed Super Tokkyū concept in Japan, its problem can be reduced.
Solutions to disadvantages
Solutions to interchangeability problems of transshipment are 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 such tight curves, a main reason to have narrow gauge. Therefore, narrow-gauge trains normally use other couplers, which makes bogie exchange meaningless.
Alternatively, a rail network comprises only narrow-gauge network could also eliminate the interchangeability problem.
If narrow-gauge rails are designed with potential growth in mind, or with same standard as standard gauge rails, then the obstacles to be faced in future growth of those rail lines would be similar to other rail gauges.
For those lines constructed to a lower standard, speed can be increased via numerous methods including realigning rail lines to increase the minimum curve radius, reducing the number of intersections, or introducing tilting trains to improve the speed of trains running on those lines.
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. Some 200-car trains operate on the Sishen-Saldanha railway in South Africa, and high-speed Tilt Trains run in Queensland. 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 nonexcess-height lines. It has 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 Transdev Auckland (Auckland suburban services).
The reduced stability of narrow gauge means its trains cannot run at the same high speeds as on broader gauges. For instance, if a curve with standard gauge rail can allow speed up to 145 km/h (90 mph), the same curve with narrow-gauge rail can only allow speed up to 130 km/h (81 mph).
In Japan and Queensland, recent permanent way improvements have allowed trains on 3 ft 6 in (1,067 mm) gauge tracks to run at 160 km/h (99 mph) and faster. Queensland Rail's Electric Tilt Train is currently the fastest train in Australia and the fastest 3 ft 6 in (1,067 mm) gauge train in the world, setting a record at 210 km/h (130 mph). The current speed record for 3 ft 6 in (1,067 mm) narrow-gauge rail is 245 km/h (152 mph), set in South Africa, 1978.
Curve radius is also important for high speeds: narrow-gauge railways allow sharper curves, which limits the speed at which a vehicle can safely proceed along the track.
Many narrow gauges are in use or formerly used between 15 in (381 mm) gauge and 1,435 mm (4 ft 8 1⁄2 in) gauge. They fall into several broad categories:
Four foot six inch gauge
4 ft 6 in (1,372 mm) track gauge also called Scotch gauge was adopted by early 19th-century railways mainly in the Lanarkshire area of Scotland. 4 ft 6 1⁄2 in (1,384 mm) lines were also constructed. Both gauges were eventually converted to standard gauge.
Four foot and 1200 mm gauge
4 ft (1,219 mm)
1,200 mm (3 ft 11 1⁄4 in)
Three foot six inch 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:
- 1,055 mm (3 ft 5 1⁄2 in) only in Algeria
- 1,050 mm (3 ft 5 11⁄32 in) for the Hejaz railway, constructed in Israel, Jordan, Lebanon, Saudi Arabia and Syria. Only a few lines survive.
Metre gauge and Italian metre gauge
Metre gauge is the system of narrow-gauge railways and tramways with a track gauge of 1,000 mm (3 ft 3 3⁄8 in). It has installations of around 95,000 km (59,000 mi).
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.
Three foot, 900 mm, and Swedish three foot gauge
Three-foot gauge railways have a track gauge of 3 ft (914 mm) and are generally found throughout North and South America, as well as Ireland and the Isle of Man.
900 mm (2 ft 11 7⁄16 in) gauge railways are generally found in Europe. Swedish three-foot gauge railways (891 mm or 2 ft 11 3⁄32 in) can only be found in Sweden.
800 mm, Two foot six inch, Bosnian, and 750mm gauge
800 mm (2 ft 7 1⁄2 in) gauge railways are commonly used for rack railways.
The imperial 2 ft 6 in (762 mm) gauge railways were generally constructed in the former British colonies.
(760 mm or 2 ft 5 15⁄16 in) Bosnian gauge and 750 mm (2 ft 5 1⁄2 in) railways are predominantly found in Russia and Eastern Europe.
Two foot and 600 mm gauges
Gauges: 2 ft (610 mm) gauge railways were generally constructed in the former British colonies. 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) were present in Europe
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.