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Standard gauge

As railways developed and expanded one of the key issues to be decided was that of the rail gauge (the distance between the two rails of the track) which should be used. The eventual result was the adoption throughout a large part of the world of a standard gauge allowing inter-connectivity and the inter-operability of trains. The distance between the inner sides of the rails in this gauge is 1435 mm (4 ft 8½ in). Currently 60% of the world's railway lines are built to this gauge.

In the United Kingdom the standard gauge was at first 4 feet 8 inches (1422 mm) but it was soon widened slightly. In the United States, because some early trains were purchased from the UK, parts of the rail system, mainly in the north-east, adopted the same gauge. However, until well into the second half of the 19th century the UK and the USA had several different gauges of track. The American gauges slowly converged as the advantages of equipment interchange became more and more apparent; the destruction of much of the South's broad gauge system in the American Civil War hastened this trend.

Origin

There is no good reason for this particular gauge to have become the standard, other than perhaps it was more widespread than any other. In fact, many engineers have considered it less than ideal. A smaller gauge offers cheaper construction but at the cost of restricted speeds owing to reduced stability. Broader gauges are theoretically more stable at speed and allow larger, wider, heavier loads.

In the UK, a Royal Commission in 1845 reported in favour of the 4 ft 8½ in (1435 mm) gauge on the grounds that its network was eight times larger than that of the rival 7 ft ¼ in (2140 mm) gauge adopted principally by the Great Western Railway. The subsequent Gauge Act of 1846 ruled that new railways should be built at 4 ft 8½ in (1435 mm), but nevertheless allowed the broad gauge companies to continue expanding their networks. After an intervening period of mixed-gauge operation (tracks were laid with three running-rails), the Great Western finally converted its entire network to the standard gauge in 1892.

A popular urban legend traces the origin of the 4 ft 8½ in (1435 mm) gauge even further back, pointing to the evidence of rutted roads dating from the Roman Empire. This legend is mostly false, however, except inasmuch that it shows a historical tendency to place the wheels of vehicles approximately five feet (1500 mm) apart.

See also: Rail gauge, Broad gauge, Narrow gauge, Dual gauge.

Ideal gauge

There has been much controversy about what constitutes the ideal gauge. From the modern perspective, it can be seen that gauge was less important than the original supporters of broader or narrower gauges held it to be:

• The heaviest trains in the world run on standard gauge track in Australia and North America. The gauge is not the limiting factor in running heavier trains.
• The fastest trains in the world also run on standard gauge in Japan and Europe, where speeds over 300 km/h are attained.
• Very heavy trains run on the narrow gauge of 3 ft 6 in (1067 mm) in Queensland (Australia) and South Africa. A somewhat narrower gauge does not seem to materially affect the weight of trains that can be run.
• Fairly fast trains can run even on narrow gauge track, as can be seen in Queensland.
• It is possible to build a light standard-gauge line about as cheaply as a narrow-gauge line. For example, a tram.
• It is possible to build a narrow-gauge line to as heavy-duty a standard as a standard-gauge line.
• Loading gauge, axle load, compatibility of couplings, continuous brakes, signalling and radio systems are also important.

With the benefits of hindsight, little was gained by building railway systems to narrower (down to about 3 ft (900 mm) or broader, up to about 7 ft (2100 mm) gauges, and this was at the cost of nil interoperability.

Only in gauges of less than 3 ft (900 mm) can a railway be built more cheaply than is possible with standard gauge.

It can be argued therefore, that the original uniform gauge adopted by Stephenson in 1830 can serve most of the tasks performed by gauges from 3 to 7 ft (900 to 2100 mm), albeit with a mini gauge of about 2 ft (600 mm) for cane tramways, underground mine railways, plus mountain, construction, temporary and military railways. Plus children's railways.

For interoperability, if possible, the mini-gauge trams should be able to piggy back on top of standard gauge flat wagons, to reach workshops and other mini gauge lines to which they are not otherwise connected. Piggyback operation by the trainload occurred as a temporary measure between Port Augusta and Maree during gauge conversion works in the 1950's.

Break of Gauge

When a railway line of one gauge meets another railway line of a different gauge, there is a break of gauge. A break of gauge is all cost and inconvenience and little benefit.

Some of the problems include:

• Transhipment of goods.
• Transhipment of passengers, including passengers sleeping in sleeping cars.
• Breaking of loads where capacity of wagons on each system do not match, creating an opportunity for damage and theft.
• Insufficient wagons, and inability of one system to loan wagons to other system.
• Bypass routes around accidents not possible because of differences in gauge.

Cane tramways of 2 ft (600 mm) gauge carry almost exclusively sugar cane, and there is little through traffic to cause a break of gauge problem.

Break of gauge can be by passed with "bogie exchange" or "variable gauge axles", or rarely, by loading the trains of one gauge onto wagons of the other gauge.

The Channel Tunnel between Great Britain and Europe has no break of rail gauge (both sides are 1435 mm), but the small loading gauge on the British side excludes all normal sized European rolling stock.

Model railway

In model railroading, Standard gauge was originally an effort by Lionel Corporation to corner the U.S. market in the early years of the 20th century. Lionel standardized its offerings on three-rail track with a gauge of 2 1/8 inches (54 mm) between the outer rails, making it incompatible with Gauge 1 offerings from European manufacturers. Lionel then registered a trademark on Standard Gauge. Other American companies followed Lionel's lead, standardizing on Lionel's new standard but calling it Wide gauge in order to avoid infringing on Lionel's trademark.

Standard gauge fell out of favour in the 1930s because of its high cost, and Lionel discontinued its Standard gauge offerings in 1940.

Although scale modeling was not of primary concern, Standard gauge's scale is generally accepted at 1:26.59, making it somewhat smaller than G scale.

More recently, standard gauge has come to mean scale modelling in which the track is accurately scaled to real-world standard gauge. This is opposed to narrow gauge modeling, which models real-world narrow gauge, or off-scale modeling, where track is not true to scale, such as in O gauge.