Previous Article   Next Article

Note: To search for something specific use the CS Museum search box to the left.

January 8, 2002

Hereís an interesting explanation of a question that may not have occurred to you. File this under ďTransportation Facts.Ē (Iím obliged to an anonymous friend for this curious bit of information.)

The U.S. standard railroad gauge (width between the two rails) is 4 feet, 8.5 inches. Thatís an exceedingly odd number.

Q. Why was that gauge used?
A. Because thatís the way they built them in England, and the U.S. railroads were built by English expatriates.

Q. Why did the English build them like that?
A. Because the first rail lines were built by the same people who built the railroad tramways, and thatís the gauge they used.

Q. Why did ďtheyĒ use that gauge then?
A. Because the people who built the tramways used the same jigs and tools that they used for building wagons which used that wheel spacing.

Q. Okay! Why did the wagons have that particular odd wheel spacing?
A. 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 thatís the spacing of the wheel ruts.

Q. So who built those old rutted roads?
A. The first long distance roads in Europe (and England) were built by Imperial Rome for their legions. The roads have been used ever since.

Q. And the ruts in the roads?
A. Roman war chariots first formed the initial ruts, which everyone else had to match for fear of destroying their wagon wheels. Since the chariots were made for (or by) Imperial Rome, they were all alike in the matter of wheel spacing.

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

Specifications and bureaucracies live forever. So the next time you are handed a specification and wonder what horseís behind came up with it, you may be exactly right, because the Imperial Roman war chariots were made just wide enough to accommodate the back ends of two war horses. Thus, we have the answer to the original question.

Now the extraterrestrial twist to the story.

When we 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 SRBís. The SRBís are made by Thiokol at their factory in Utah. The engineers who designed the SRBís might have preferred to make them a bit fatter, but the SRBís had to be shipped by train from the factory to the launch site. The railroad line from the factory had to run through a tunnel in the mountains. The SRBís had to fit through that tunnel. The tunnel is slightly wider than the railroad track, and the railroad track is about as wide as two horsesí behinds.

So, the major design feature of what is arguably the worldís most advanced transportation system was determined over two thousand years ago by the width of a horseís behind.

And you wonder why itís so hard to get ahead in this world.