Train Set: Track Two

Announcement: Imperial Chariot Break

There’s some old infrastructure lore about the reason why American rails have such a specific spacing – this persistent story is that American rail gauges – as in, the distance between the metal rails – can be directly traced all the way back to the wheel spacing of ancient Imperial Roman chariots. And the logic goes something like this: American rails are spaced four feet, eight-and-a-half inches apart; and that seemingly odd number comes from English spacing standards; and those standards, in turn, were based on wagon construction dimensions; and those had to be standardized so wagons could ride in existing ruts; and those ruts were initially formed by the Roman Empire.

Now, there is some truth to this train of thought, but the legend itself, which has persisted for over a century, is mostly fanciful. For one thing, ancient Roman roads were built more for foot traffic than for chariots. Plus, current gauges were far from inevitable – for a long time, there was no standard gauge in the United States – a variety were used. Ultimately, the relative similarity between modern rail line gauges and ancient rutways are tied more to design than to history. Times may have changed, but the physical constraints of vehicles have remained relatively consistent – axles need to span far enough to support the structures above them, but they can’t be too wide or they might snap.

So modern gauges aren’t really products of Imperial Rome. History rarely lets us trace such a direct line across such a long period of time. Still, it’s also not entirely coincidental that rail spacing tends to fall into a certain range. Because, from a usability perspective, and an engineering standpoint … it turns out: the overall needs and limitations of ancient chariots, medieval wagons, and contemporary railroads are (broadly) more similar than they are different.