When reading about trains, you may have heard the terms “narrow gauge” or “standard gauge” or “broad gauge”. What do those mean?
What is Gauge?
Simply put, “gauge” is the distance between the two rails of a railroad track. Specifically it’s the distance between the inside of the two rails.
The gauge is measured in either the Imperial or metric system.
What is Standard Gauge?
“Standard” gauge is measured as 4 feet 8 and a half inches between inside rails, often shown as 4′ 8 1⁄2″. This is the most widely used gauge in the world.
The origin of this gauge is uncertain. Some attribute it to the distance between wheels on Roman carriages (see this Snopes article) but it was first used in the railway context by English railway pioneer George Stephenson in the 1820s. It was widely adopted in England, other parts of Europe and North America and continued to spread around the world.
What is Narrow Gauge?
Narrow gauge is any track laid with the rails closer together than standard gauge. There are several narrow gauges, with three-foot (3′) being the most common. Many mountain railways were constructed in narrow gauge to save money, with the theory that a narrower track required less blasting, smaller tunnels and shorter ties.
Today there are few narrow gauge railways remaining in North America. The Durango and Silverton tourist railway is probably the most well known narrow gauge railway still running.
There are smaller narrow gauge tourist railways. One could consider the “toy” railways in some amusement parks as narrow gauge railways. The “two foot railways” in the state of Maine in the USA were famous for their extremely narrow gauge. The Wiscasset, Waterville & Farmington Railway operates on two foot gauge tracks.
What is Broad Gauge?
Broad gauge is any track laid with the rails farther apart than standard gauge. When railways were first being built in England, some were built in the “broad” gauge with the theory that wider railway cars were more stable and provided a more comfortable ride.
Today the most common broad gauge is “Russian gauge”, at 5 feet (1,524 mm). It was redefined to 1520mm in the Soviet Union. Finland and Estonia also use this gauge.
What is Metre Gauge?
Meter gauge (or metre gauge) is a specific type of narrow gauge where the rails are one metre (1000 mm) apart. This is equivalent to 3′ 3 3/8″, which is definitely easier to say in the Metric system.
Sometimes other narrow gauges are expressed in Metric. For example the 3’6″ variety of narrow gauge is 1067mm and 3’0″ narrow gauge is 915mm.
Dual Gauge
It is possible to have tracks that support two different gauges, by laying a third rail inside the wider gauge. For example, track could support standard and narrow gauge at the same time.
For example, this was done in the province of Newfoundland at the Port aux Basques port. Standard gauge rail cars were brought over from the Canadian mainland by ferry, then landed in the port on standard gauge tracks. There, the “trucks” under the rail cars were switched for narrow gauge trucks and the cars continued on the Newfoundland narrow gauge system.
Spain has a significant amount of dual gauge track, as their existing system was broad gauge (1668mm) but they have a growing amount of standard gauge track to connect to the rest of Europe. Portions have been converted to dual gauge or just to standard gauge.
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