A narrow-gauge railway is a railway with a track gauge narrower than 1,435 mmstandard gauge. Most narrow-gauge railways are between 600 mm and 1,067 mm.
Australians generally assumed in the 1850s that railways would be built by the private sector. Private companies built railways in the then colonies of Victoria, opened in 1854, and New South Wales, where the company was taken over by the government before completion in 1855, due to bankruptcy. South Australia's railways were government owned from the beginning, including a horse-drawn line opened in 1854 and a steam-powered line opened in 1856. In Victoria, the private railways were soon found not to be financially viable, and existing rail networks and their expansion were taken over by the colony. Government ownership also enabled railways to be built to promote development, even if not apparently viable in strictly financial terms. The railway systems spread from the colonial capitals, except for a few lines that hauled commodities to a rural port.
With railways, a break of gauge occurs where a line of one track gauge meets a line of a different gauge. Trains and rolling stock generally cannot run through without some form of conversion between gauges, leading to passengers having to change trains and freight requiring transloading or transshipping; this can add delays, costs, and inconvenience to travel on such a route.
The first railway in colonial South Australia was a line from the port of Goolwa on the River Murray to an ocean harbour at Port Elliot, which first operated in December 1853, before its completion in May 1854.
Railways with a track gauge of 3 ft 6 in were first constructed as horse-drawn wagonways. The first intercity passenger railway to use 3 ft 6 in was constructed in Norway by Carl Abraham Pihl. From the mid-nineteenth century, the 3 ft 6 in gauge became widespread in the British Empire. In Africa it became known as the Cape gauge as it was adopted as the standard gauge for the Cape Government Railways in 1873, although it had already been established in Australia and New Zealand before that. It was adopted as a standard in New Zealand, South Africa, Indonesia, Japan, the Philippines, Taiwan, and Queensland in Australia.
There were more than a thousand British narrow-gauge railways ranging from large, historically significant common carriers to small, short-lived industrial railways. Many notable events in British railway history happened on narrow-gauge railways including the first use of steam locomotives, the first public railway and the first preserved railway.
The rail network in Queensland, Australia, was the first in the world to adopt 1,067 mm narrow gauge for a main line, and, in 2013, was claimed to the second largest narrow gauge network in the world, consists of:
Rail transport in Australia involves a number of narrow-gauge railways. In some states they formed the core statewide network, but in the others they were either a few government branch lines, or privately owned and operated branch lines, often for mining, logging or industrial use.
Although most railways of central and eastern Canada were initially built to a 5 ft 6 in broad gauge, there were several, especially in Atlantic Canada and Ontario, which were built as individual narrow-gauge lines. These were generally less expensive to build, but were more vulnerable to frost heaving because vertical displacement of one rail caused greater angular deflection of the narrower two-rail running surface. Most of the longer examples were regauged starting in the 1880s as the railway network began to be bought up by larger companies.
Rail transport in Central America consists of several isolated railroad lines with freight or passenger service. The most famous one is the Panama Canal Railway, the oldest transcontinental railroad in the world, connecting Panama City with Colón since 1855. Other railroads in Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama were built by private and public investors mainly to facilitate the transport of local agricultural produce to export markets and harbors. Their market share and profitability went into decline in the second half of the twentieth century and most lines have been decommissioned by the end of the 1990s. As of 2018, railroads operate locally in Honduras, Costa Rica and Panama only; all rail transport has been suspended in Belize, El Salvador, Guatemala and Nicaragua. The railways still operating do not cross national borders.
Bogie exchange is a system for operating railway wagons on two or more gauges to overcome difference in the track gauge. To perform a bogie exchange, a car is converted from one gauge to another by removing the bogies or trucks, and installing a new bogie with differently spaced wheels. It is generally limited to wagons and carriages, though the bogies on diesel locomotives can be exchanged if enough time is available.
The track gauge adopted by the mainline railways in Ireland is 1,600 mm. This unusually broad track gauge is otherwise found only in Australia, in the states of Victoria, southern New South Wales and South Australia, as well as in Brazil.
Railways with a track gauge of 5 ft 3 in fall within the category of broad gauge railways. As of 2022, they were extant in Australia, Brazil and on the island of Ireland.
Various track gauges are used in Hong Kong on different railways and railway lines.
Sweden once had some fairly extensive narrow-gauge networks, but most narrow-gauge railways are now closed. Some were physically converted to 1,435 mmstandard gauge and some remain as heritage railways. The most common narrow gauge, 891 mm, exists only in Sweden. A smaller 3 ft 6 in gauge network existed, and 600 mm gauge was used mostly by smaller, industrial railways. Still other but lesser used gauges in the country were 693 mm, 802 mm, 1,099 mm, 1,188 mm and 1,217 mm, all converted or removed.
Europe inherited a diversity of rail gauges. Extensive narrow-gauge railway networks exist in Spain, Central Europe and Southeastern Europe.
Asia has many narrow-gauge railways. The railways of Japan, Indonesia and the Philippines are predominantly 1,067 mm narrow gauge. Those in mainland Southeast Asia, which includes Vietnam, Cambodia, Laos, Thailand, Myanmar and Malaysia, are predominantly metre gauge. The proposed ASEAN Railway would be standard or dual gauge, using metre- and standard-gauge regional railway networks and linking Singapore through Malaysia, Thailand, Laos and Vietnam to China's standard-gauge rail network. In Western Asia, Jordan uses 1,050 mm narrow gauge.
Numerous narrow-gauge railway lines were built in Oceania, most in 3 ft 6 in, 2 ft 6 in and 2 ft track gauge.
The Kadina–Brinkworth railway line was a railway line on the South Australian Railways network.
Kadina railway station was located on the junction of the Balaklava-Moonta railway line and the Kadina-Brinkworth railway line. It served the town of Kadina.
