Standard gauge
As the railway developed and expanded one of the key issues was the gauge (rail separation) of track to be used. This eventually resulted in the adoption of a standard gauge to allow inter-connectivity and inter-operability of the trains. It means that the distance between the inner sides of the rails is 1.435 metres (4 feet 8.5 inches). Currently 60% of the railway tracks in the world are this gauge.
In the United Kingdom the gauge was at first 4 feet 8 inches but it was soon widened slightly to the standard gauge. In the United States, because some early trains were purchased from the UK, part of the rail system, mainly in the north-east, adopted the same gauge. However, until well into the second half of the 19th century both 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 the trend.
In the UK, a Royal Commission in 1845 reported in favour of the 4ft 8.5in gauge on the grounds that its network was eight times larger than the rival 7ft gauge adopted principally by the Great Western Railway. The subsequent Gauge Act 1846 ruled that new railways should be built at 4ft 8.5 in, but nevertheless allowed the broad gauge companies to continue expanding their networks.
A popular urban legend traces it even further to rutted roads dating back to the Roman Empire.
See also: Broad gauge, Narrow gaugeOrigin
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 a cost of restricted speeds through reduced stability. Broader gauges are more stable at speed and allow larger, wider, heavier loads.
