On Railroad Tracks and Roman Chariots

by Brian Dunning
February 8, 2022

I'd like to open this episode with a warning. The Internet is full of little meme graphics festooned with text that often makes some historical claim, and my caution to you is that — hold onto your hats — they may not all be 100% factually accurate. One of these is the perennial claim, first put forward in a Popular Mechanics article in 1905, that the standard gauge of the world's railroads goes all the way back to the ruts in Roman roads made by war chariots. It seems logical but also raises a few red flags. Honestly, when I came into this, I had no idea whether I was going to find that it was completely true or completely false. But this is Skeptoid, so we are legally obligated to get to the truth.

Here is the basic story. Widely available all over the Internet is some variation on the following narrative:

Did you know that the US Standard railroad gauge (distance between the rails) is 4 feet, 8 1/2 inches?

Why? Because that's the way they built them in England, and the US railroads were built by English expatriates.

Why? Because the first railway lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used.

Why? Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing.

Why? Because, if they tried to use any other spacing the wagon wheels would break on some of the old, long distance roads. Because that's the spacing of the old wheel ruts.

The first long distance roads in Europe were built by Imperial Rome for the benefit of their legions. The Roman roads have been used ever since.

The original ruts, which everyone else had to match for fear of destroying their wagons, were first made by the wheels of 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 question. The United States standard railroad gauge of 4 feet, 8 1/2 inches derives from the original specification for an Imperial Roman army war chariot.

So that's a lot of factual claims. Sounds pretty airtight, doesn't it? Well, let's go through it point by point, in reverse order.

The first (and particularly painful) point of failure for the legend is there was really no such thing as a Roman war chariot. Chariots in Rome were used for racing and in parades, not in warfare, or for daily transportation. Wars were not fought on roads or flat racetrack surfaces, but on natural terrain, where chariots were not suitable. Thus, there was no "official specification" for "Imperial Roman war chariots." At least one book claims Julius Caesar himself issued an edict to standardize this, but no evidence exists to support that. In addition, it's improbable, as long before the time of Caesar, cavalry horses had been bred large enough that the military would have had no need for chariots. Neither specialized racing chariots nor fancy parade chariots would have been in daily use on the rutted Roman roads, so then what else could have caused those ruts?

There are plenty of academic papers written on the use of streets in Roman cities, and none of them mention chariots. Vehicle traffic consisted of hand-drawn two-wheeled carts; two and four-wheeled wagons pulled by one or two horses, donkeys, or oxen; and even sledges on runners. One paper which looked at vehicles throughout the Western Mediterranean region found that hand and donkey cart track widths ranged from 115-120cm, single-horse carts ranged 135-140cm, and pair-drawn carts ranged from 145-170cm. Four feet, 8.5 inches comes out to 143.5cm, so most Roman vehicles had smaller axle widths than a standard gauge railway, but some were bigger, a few quite a bit bigger.

The rut systems found in Roman roads tell a similar story. It is simply a false urban legend that track widths of Roman ruts are all 4 feet, 8.5 inches (go there and measure them yourself). Many papers have been published describing the ruts in Roman roads. In some regions, ruts made by vehicles would be repaired by repaving the roads; but in many other places, ruts were deliberately cut and still bear visible chisel marks. In most cases, the width of artificial ruts was designed for a particular vehicle that was frequently used there. In cities this would often be hand carts. On longer roads the tracks would be wider to accommodate larger freight vehicles. I wish I could give common or usual measurements, but in the many articles I read, the track width of artificial ruts was all over the place. Most were smaller than standard gauge — in the 120-135cm range for hand and donkey carts — and some were bigger. What definitely cannot be claimed is that there was a standard track size. It also can't be claimed that the ruts were made by or for chariots, and certainly not war chariots.

In short, everything about 4 feet, 8.5 inches coming from Roman war chariots is a complete, utter, and total non-starter.

So to continue evaluating this urban legend, we can skip on down a bit. The next thing it claims is that later European wagons used this same width because if they were going to drive in the Roman ruts with a non-conforming axle width, it would have "broken their wheels". It's true that if you needed a wagon to travel a particular route, and that route is on an old Roman road with artificial ruts, you'd do better to match that width to get a smoother, more efficient ride. But what we've already learned is that those ruts were not all the same size, and also that rutted sections of road were fragmented and inconsistent. Wagons built to any given specification would have found benefit only on a few scattered, noncontiguous sections of road.

Accordingly, we have empirical evidence that wagons were not standardized. One book on the history of transport included a study of English wagons from the era when tramways were first starting to be built. It found substantial regional variations within extremes of about 130 and 190cm. No standard width.

The next step in the urban legend — that "the people who built the tramways used the same jigs and tools that they used for building wagons" — doesn't make any sense at all. Casting iron axles and wheels would not use a single tool or jig involved with the manufacture of wooden wagon wheels. Literally, not even the slightest bit of crossover. This is a horrible logic fail by whomever originally wrote this urban legend.

However, what we should expect to see is that, since the first tramways were drawn by two to six horses side-by-side, such vehicles would have been roughly the same width as Roman two-horse carts. Draft horses in one era were about the same size as draft horses in the other, and that's not because of any mythical Imperial edicts or official specifications. It's just about how big horses are. So the track widths are in the same neighborhood — but again, 4 feet, 8.5 inches was only one example among many different gauges.

When the English first started building railed tramways, one of the more common of the many competing gauges was five feet, measured from the outside edge of the track. Five feet is a good round number, easily remembered, and easily shared with contractors and manufacturers. Track was generally two inches wide, which gave an inside gauge of 4' 8". Track gauge is measured from the inside edge because that's where the vertical flange on the wheel is, which is what holds the axles atop the two parallel tracks.

It is fair to point out that Romans also used a unit of length called the foot, and their foot was only a tiny fraction shorter than the modern Imperial foot. It's not inconceivable that at some point, some Roman influencer could have said "Hey, let's standardized on five feet, because that's a good round number everyone can remember." It's a nice idea, however the evidence shows that while that gauge can indeed be found in some Roman ruts, it's in the minority. Recall that Roman vehicles and Roman ruts were all over the place. They demonstrably did not standardize.

But standardizing is something that did have to happen — and this need arose earliest and most urgently during the American Civil War. It came at a time of turmoil in the American rail system. During the 19th century, tramways gave way fast to steam locomotives. Gauges were all over the place, based on many factors. Mines needed tiny locomotives to fit in cramped tunnels. The great English engineer Isambard Kingdom Brunel used a massive 7-foot gauge for maximum stability for the high-speed rail service he anticipated. Narrow gauges saved a lot of weight and made the tracks easier to build and maintain. Wider gauges were better able to plow through snow. Narrower gauges could handle turns of a smaller radius. Regional railroads, such as those on different sides of rivers or mountain ranges, saw little benefit in consolidating with one another.

Once the war broke out, efficient nationwide transportation of troops and materials was literally a national emergency. The greatest problem was that of breakbulk cargo, which had to be manually unloaded from a train of one gauge and manually loaded onto a train of another. This transfer of cargo was, for a time, among the most serious emergencies the United States faced. Abraham Lincoln proposed a national standard of 5 feet, but the priority had to be to choose a standard that could be implemented rapidly. It turned out that there was one gauge, most used in the northeastern lines, that was just common enough that it emerged the winner. It was called Stephenson gauge, after English railroad engineer George Stephenson. He had been perhaps the principal inventor of the steam locomotive. No record survives that tells us exactly how Stephenson came up with his gauge, but there are a couple of perfectly reasonable theories. One is that he was simply most familiar with that gauge as he'd worked with it before on tramways; another hearkens back to "five feet is a good round number" minus two inches of width for each track, and plus a half inch to allow for a quarter inch of play on each wheel. So when the Pacific Railroad Act of 1863 was passed, it dictated that the transcontinental railroad should be built to a gauge of 4 feet, 8.5 inches, as would all other lines needed for the war effort.

As far as the urban legend's final point goes — that US railroads were built by English expatriates — that's demonstrably false as well. The first US locomotives were indeed purchased from England, and some of them used the Stephenson gauge. A lot of other railroad equipment was purchased from England, because they'd started building them first. But by 20 years before the Civil War, American industry was producing far more locomotives than all of Europe and was exporting them. Certainly there were some English expatriates employed by the American lines, but it's hardly true to say that US railroads were either built or designed by them.

Now, Skeptoid is hardly the first show to tackle the historicity of this particular urban legend. Snopes, the Straight Dope, and others have done it before. Generally they all conclude with calling the legend partially true, because the gauges are indeed very similar, and the average width of two horses played a role at several stages in the evolution of tracks for vehicles. I regret that I cannot concur. The influence of horse width at different times in history is very different from the definitely-false claim of an official Roman specification for war chariots directly informing the gauge for 55% of the world's railroads.

People love oversimplified explanations that make it possible to comprehend a complicated subject — and it is a complicated subject; the book American Narrow Gauge Railroads that was one of my primary sources for this is almost 600 large-leaf pages of dense history. It's one reason conspiracy theories are popular; they replace complexity with simplicity. Whenever you hear such an explanation for anything, you have very good reason to be skeptical.

By Brian Dunning
Follow @BrianDunning