Standard Gauge - History

History

As railways developed and expanded one of the key issues to be decided was that of the track gauge (the distance, or width, between the inner sides of the rails) that should be used. The eventual result was the adoption throughout a large part of the world of a “standard gauge” of 4 ft 8½ in allowing inter-connectivity and the inter-operability of trains.

In England some early lines in colliery (coal mining) areas in the northeast of the country were built to a gauge of 4 ft 8 in (1,422 mm); and in Scotland some early lines were 4 ft 6 in (1,372 mm) (Scotch gauge). By 1846, in both countries, these lines were widened to standard gauge. Parts of the United States rail system, mainly in the northeast, adopted the same gauge because some early trains were purchased from Britain. However, until well into the second half of the 19th century Britain and the USA had several different track gauges. The American gauges converged over time as the advantages of equipment interchange became increasingly apparent; notably, the South's 5 ft (1,524 mm) broad gauge system was converted to be compatible with standard gauge over two days, beginning May 31, 1886. See Track gauge in North America.

With the advent of metrication, standard gauge was redefined as 1,435 mm, a reduction of 0.1 mm, but well within existing tolerance limits. The exception is the United States where standard gauge continues to be defined in terms of customary units.