Getting Stuck in the Standards Rut

The US standard railroad gauge (width between the two 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 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.

Ruts in the Via Appia Antica in Rome

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

And the ruts in the roads? 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 specification for an Imperial Roman war chariot. Specifications 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 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 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 SRBs. The SRBs are made by Thiokol at their factory in Utah. The engineers who designed the SRBs might have preferred to make them a bit fatter, but the SRBs had to be shipped in pieces by train from the factory to the launch site. At the launch site they were re-assembled and sealed by o-rings at the joints.

The railroad line from the factory had 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 is about as wide as two horses' behinds. So, the major 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 wonder why it's so hard to get ahead in this world...

Above is the often cited myth authored by unknown, but it seems to be posted all over the web. Taking it a step further, one could argue that the "meta-cause" of the Shuttle Challenger disaster was the indirect result of incremental thinking in design and was set in motion over two thousand years ago by the width of a horse's behind.

The actual history of railroad gauges is more interesting and seems to parallel present day standardization issues well.

Denny S. Anspach suggest that if the Roman ruts matched the english waggonways and early railroads, it was not that George Stephenson copied the Roman road ruts, they simply responded to the same natural need: the size of the most efficient and stable vehicle that could be pulled by one horse. Matt Wall also debunks this horseshit tale referring to engineering needs of the day. The standard gauge was the widest original width you could reliably make an iron axle (pre-bessemerized steel days) that would support the then-weight of locomotives.

However the standards story isn't too far off and once a critical mass is reached, any advances in technology could not change the standard. Economies of scale and standardization helped mass production, and interoperability enabled an actual network as opposed to a conglomeration of vaguely interconnected subsystems. This de-facto standardization created the lock-in.

There is more history on this urban legend in other places. But the interesting part is how it relates to competition and how critical mass is used to the incumbents' advantage.

The economics of networks also applies to standardization on the web. It would seem from the NYT's interview with economist John Steele Gordon titled "To Gauge the Internet, Listen to the Steam Engine", that he would only agree. Check How Microsoft is Building a Global Monopoly, by Nathan Newman, and Making Microsoft Safe for Capitalism by James Gleick.

Thanks to Mark Smucker for the extra research.