Back in 1998, some friends of mine forwarded me this story1 that underscores the mindlessness of tradition (a fellow who claims to be the author has posted it here):
US Standard Railroad Gauge or
How MilSpecs Live Forever
The US Standard railroad gauge (distance between the rails) is 4 feet, 8.5 inches. That's an exceedingly odd number. Why was that gauge used? Because that's the way they built them in England, and the US railroads were built by English expatriates. Why did the English people build them like that? Because the first rail lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used.
Why did "they" use that gauge then? Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing. Okay! Why did the wagons use that odd wheel spacing? Well, if they tried to use any other spacing the wagons would break on some of the old, long distance roads, because that's the spacing of the old wheel ruts.
So who built these old rutted roads? The first long distance roads in Europe were built by Imperial Rome for the benefit of their legions. The roads have been used ever since. And the ruts? The initial ruts, which everyone else had to match for fear of destroying their wagons, were first made by Roman war chariots. Since the chariots were made for or by Imperial Rome they were all alike in the matter of wheel spacing.
Thus, we have the answer to the original questions. The United States standard railroad gauge of 4 feet, 8.5 inches derives from the original specification (Military Spec) for an Imperial Roman army war chariot.
MilSpecs and Bureaucracies live forever.
So, the next time you are handed a specification and wonder what horse's ass came up with it, you may be exactly right. Because the Imperial Roman chariots were made to be just wide enough to accommodate the rear-ends of two war horses.
My very clever friend Sean T. Brady composed this reply2 showing that apparently mindless traditions often draw on wisdom beyond our awareness:
Everything the author writes is correct (except for the bit about the rear-ends of the horses). But he misses the whole experiment with narrow-gauge railroads at the end of the 19th century, when railroad builders in the US realized that they could save a fortune by building narrower gauge railroads, and trains to match. Problem was that the new trains could carry far less weight than even their reduced proportions would suggest. At the end of a long and expensive period of trial and error, the railroad builders reverted to the standard gauge, which engineers later discovered provides the optimal load carrying capacity, i.e. for the same strength axle, the highest number of pounds per inch of width.
The lesson to take home from this exchange is that we who live in this sliver of history called the present are not necessarily wiser than those of previous slivers, and that we unthinkingly discard their accumulated wisdom only at our loss. As I quoted Chesterton last week, only when we understand a tradition are we qualified to judge its merit.
 Interesting note about the source of the story here. According to this site, the author of the story is Bill Innanen  Rewrite of a longer reply that Sean had sent me long before, but which we both misplaced.
I wrote the "MilSpec" story on 9 Feb 1994 as a humor posting for a private mailing list. You can see the original posting on my web site at [broken link]. I had never seen the story in writing, but I had heard a similar piece on the radio some years previous. I think it was on the CBS radio series "The Osgood Files" but I'm very uncertain of that. It'd be something that Charles Osgood would do, though. Because I deal professionally with the military R&D world, the story stuck with me through the years.
 Rewrite of a longer reply that Sean had sent me long before, but which we both misplaced.