An urban legend circulated since the mid 1990s starts by asking why the standard railway gauge (distance between the rails) is 4 feet 8½ inches.
The most recent version of the story starts by claiming that the 4 ft. 8½ in. gauge limited the diameter of the solid-rocket boosters (SRBs) used on the Space Shuttle, because they were made in Utah in the western USA and transported to the launch site in Florida by rail through tunnels “just a little wider than the gauge.”
The “answer” is that English engineers designed American railways. At the time, 4 feet 8½ inches was the standard railway gauge in England, because the tracks were said to have been laid on top of ruts in roads made by Roman war chariots. In turn, the Imperial Roman war chariots were said to have been built to a standard that set their wheel spacing to 4 feet 8½ inches. So an ancient Roman military standard was claimed to be the origin of the Standard Gauge and hence a limit on the diameter of space shuttle boosters.
These curious details now are going round the globe on the Internet. There now are many mentions of them in Norwegian, as on the Norwegian Broadcasting (NRK) debate pages (external link, in Norwegian).
Though amusing, the story isn’t true, save that the Standard Gauge now used by more than 60% of the world’s railways is 4 feet 8½ inches (1435 mm). The “facts” of the story are fictional. To begin with, The Roman Legions didn’t use chariots in battle, because they were unstable and could be used only in flat terrain and consequently were obsolete by 600 BC. They used armoured infantry and cavalry.
The first railway gauge was set not for rails laid on roads, but rather for rails laid in mines. It was 4 feet 8 inches. But in building the Liverpool and Manchester Railway that opened in 1830, railway engineer and locomotive builder George Stephenson added half an inch of free wheel movement to eliminate binding on curves.
The width of a load carried by rail depends on the width of the rail vehicle used, not the spacing between the underlying rails. Around the world, there are thousands of container well wagons about ten feet wide, designed for carrying 8 ft. wide by 20 ft. long intermodal containers. Most standard gauge passenger trains are made up of carriages about 10 ft. wide. The Shuttle’s SRBs are 12.71 ft. in diameter, about the same as the width of battle tanks routinely carried, tied down by chains, on flatbed railway wagons. Finally, the diesel and electric locomotives that pull these trains are about 11 ft. wide.
The first military standard for a gauge of 4 feet 8½ inches was not Roman. It was American, an outcome of the United States Military Railway organisation founded in 1862 to facilitate rail transport during the American Civil War. Despite these facts, the urban myth of a Roman connection was so persistent that in 2001, the US Defense Standardization Program debunked it in an in-depth history of the Standard Gauge in its Journal.
Further readingThe historically factual story of the Standard Gauge, “Roman Chariots, Railroad Tracks, MilSpecs, and Urban Legends,” by Stephen Lowell of the Defense Standardization Program, was published in August 2001 edition of the Defense Standardization Program Journal, pages 14-16.
The complete text is also available on the NASA website.
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