Does the statement, “We’ve always done it that way” ring any bells?

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 English
expatriates built the US Railroads.

Why did the English 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 have that particular odd wheel spacing?

Well, if they tried to use any other spacing, the wagon wheels would
break on some of the old, long distance roads in England, because
that’s the spacing of the wheel ruts.

So who built those old rutted roads?

Imperial Rome built the first long distance roads in Europe (and
England) for their legions. The roads have been used ever since.

And the ruts in the roads?

Roman war chariots formed the initial ruts, which everyone else had to
match for fear of destroying their wagon wheels.

Since the chariots were made for Imperial Rome, they were all alike in
the matter of wheel spacing..

The United States standard railroad gauge of 4 feet, 8.5 inches is
derived from the original specifications for an Imperial Roman war

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 army
chariots were made just wide enough to accommodate the back ends of two
war horses.

Now the twist to the story

When you see a Space Shuttle sitting on its launch pad, there are two
big booster rockets
attached to the sides of the main fuel tank. These are solid rocket
boosters, or SRBs.
The SRBs are made by Thiokol at their factory at Utah. The engineers who
designed the
SRBs would have preferred to make them a bit fatter, but the SRBs had to
be shipped by
train from the factory to the launch site. The railroad line from the
factory happens to run
through a tunnel in the mountains. The SRBs had to fit through
that tunnel. The tunnel is slightly wider than the railroad track, and
the railroad track, as you now know, is about as wide as two horses’

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!