Menu ☰
The Smoke Stack

RR Facts “Training” – The Distance Between Rails: Why 4 feet, 8.5 inches?

Posted on March 15, 2017

The U.S. standard railroad gauge (width between the two rails) is 4 feet, 8.5 inches which seems like a very odd number. Why was that specific gauge used? Because that is how England built its railroad system – and U.S. railroad equipment was imported from England. But why did the English build them use that measurement? Because the first rail systems were built by those who built pre-railroad tramways, and that was the gauge that they used. Tramways used the same jigs and tools that were used for building wagons that had a specific wheel spacing.

So the standard railroad gauge is thought to be linked to the spacing of wagon wheels… but how was that distance chosen? Some of the old, long-distance roads in England had wheel ruts produced from centuries of travel. Wagon wheels had to conform to the spacing of the ruts or else the wheel mechanisms would break. The first long distance roads in Europe, including England, were built by Imperial Rome for its legions, and those early roads have been used ever since.

The ruts were first produced by Roman war chariots which all shared the same wheel spacing, and it is a logical conclusion that every vehicle thereafter had to conform to the measurement for fear of destroying its wagon wheels.

Thus the United States standard railroad gauge of 4 feet, 8.5 inches can be traced all the way back to the original specification for Imperial Roman war chariots which were made just wide enough to accommodate… the back ends of two war horses!

A final thought… the eventual standardization of the railroad gauge across the U.S., from the North to the South, was largely due to the fact that the North won the Civil War and, in the process, rebuilt much of the Southern, then fairly-independent 5-foot-gauge railway system to match its own. Had the Civil War taken a different course, with the victory of the South, the eventual standard railroad gauge used throughout North America might have been different than 4 feet, 8.5 inches!

<< Back