“The United States standard railroad gauge of 4 feet, 8.5 inches is derived from the original specifications for an Imperial Roman war chariot. … So, a major Space Shuttle design feature of what is arguably the world’s most advanced transportation system was determined over two thousand years ago by the width of a horse’s ass. … and you thought being a HORSE’S ASS wasn’t important!”
This is from TruthOrFiction.com:
There is no evidence that we could find that this is true.
In an article on www.railway.org by D. Gabe Gabriel says this tale has existed since shortly after World War II but that history does not support the claims of the story. The Roman ruts, according to Gabriel, were not for chariots but for narrow, hand-pulled carts. Although there are many places where the ruts are visible, Gabriel questions that they played a role in English railroad standards 1400 years after the last Roman legions. One of the claims of the eRumor is that the width of the ruts was affected by the need to make the chariot and it’s wheels the same width as the combined rears of the horses pulling them. Gabriel says there’s a statue by Franzoni in the Vatican museum that is regarded as the most accurate known depiction of a Roman chariot. The two horses are wider than the chariot and the chariot wheels behind them.
Where did the four-foot, eight-and-a-half-inch standard originate? Gabriel says it was from a Englishman named George Stephenson. Carts on rails had been used in mines in England for years, but the width of the rails varied from mine to mine since they didn’t share tracks. Stephenson was the one who started experimenting with putting a steam engine on the carts so there would be propulsion to pull them along. He had worked with several mines with differing gauges and simply chose to make the rails for his project 4-foot, eight inches wide. He later decided that adding another six inches made things easier. He was later consulted for constructing some rails along a roadway and by the time broader plans for railroads in Great Britain were proposed, there were already 1200 miles of his rails so the “Stephenson gauge” became the standard.
Interestingly, the 4-foot, eight-and-a-half inch width has not always been the standard in the U.S. According to the Encyclopedia of American Business History and Biography, at the beginning of the Civil War, there were more than 20 different gauges ranging from 3 to 6 feet, although the 4-foot, eight-and-a-half inch was the most widely used. During the war, any supplies transported by rail had to be transferred by hand whenever a car on one gauge encountered track of another gauge and more than 4,000 miles of new track was laid during the war to standardize the process. Later, Congress decreed that the 4-foot, eight-and-a-half inch standard would be used for transcontinental railway.