2-40. A Horse’s Ass



It seems obvious that for railways to work, the distance between tracks must be standardized. In the United States, that standard is four feet, 8 1/2 inches, or about 144 centimeters. This seems an oddly precise measurement, so how did it come to be?

The legend goes like this: US rail systems are based on British rail systems. British rail systems are based on medieval carts. Medieval carts were based on the ruts left by Roman chariots. Roman chariots were sized to accommodate two horses, side by side, and the space needed for that is 4 feet, 8 ½ inches. An Internet meme about this mentions the space shuttle’s boosters, which were sized to accommodate railroad tunnels. This forces the conclusion that the space shuttle was designed by a horse’s ass.

It’s a great story, full of logic and history and… a good deal of fiction. All one needs to realize is that the Romans moved goods by human-powered handcarts, and our lovely meme falls apart.

The real story is one of arbitrary practicality.

Railroads evolved from mine carts that were pulled by an experimental steam engine. A Englishman named George Stephenson chose the gauge of four feet 8 ½ inches after of a bit of experimenting, but with no previous measurement in mind—it’s just what worked at the mine he was using for testing. When the idea of railroads became viable, his equipment was modified and that’s the gauge that was used.

But 50 years later, George’s arbitrary measurement was just one of twenty different gauges. Different companies and inventors adjusted track widths to their own purposes, and in the 1850s, it wasn’t uncommon to find mismatched lines meeting, and then cargoes being offloaded from one sized railway to another.

The Civil War changed that. The US government dictated that there be one single gauge for all railways, so as to facilitate the movement of troops and equipment as expeditiously as possible. And the gauge they chose was four feet, eight and half inches. They chose this simply because it was the most popular gauge, and gradually, lines with other gauges were converted or abandoned.

There are other sized lines today, called “narrow gauge” railways, but these are purpose built for a single need such as moving lumber, agriculture or ores a short distance. Since they’re purpose built, they’re not standardized, and rather use a gauge that’s most cost-effective for the purpose.

So, with a little curiosity, we can take a nice, neat story and destroy it. But the real story is at least as interesting, as we can now see patterns between railways, records, video tapes, electrical systems, and even mundane things like the length of paper towel rolls. Why are paper towel rolls all 11 inches? That would be a topic for another day.

Thanks to curious person, Steve Cuno for suggesting this topic.


One width does not fit all

One width does not fit all


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One Comment

  1. The Newfoundland railway of my youth was the longest narrow gauge railway in North America at 906 miles. Being an island there was no need to standardize it with the rest of the continent.

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