Explanation: There is definitely a difference in intensity of usage between modern roads and Roman roads, but there’s also a difference in design philosophy - with the advance of technology and budget organization, it literally is cheaper to build something to require maintenance every ten years than to overengineer it to the point where it lasts longer for a far greater lifetime expense. There’s nothing wrong with that - it is, in fact, more effective. But we’re memeing right now, and it is a bit funny.
The other aspect is that the road types today don’t equate to what Roman roads were meant for. In modern parlance, we would say that Roman roads are akin to highways, going between major places and prioritized speed and mobility. Basically the Interstate freeways of the day. Durable and all-weather.
But Roman roads don’t really analogize to the sprawling suburban streets of America and other car-obsessed places. For a question about the costs of road vs rail, I wrote that the way freeways are built is still more-or-less recognizable from the Roman approach: dig down and remove soil, add different layers of material, put a smooth-ish surface on top. But today’s suburban and residential asphalt roads are explicitly a product of the availability of cost-cutting technology, where asphalt can basically be laid atop the natural soil.
That allows more road to be laid for cheap, but of a lower quality than highways. And that’s fine for a neighborhood street.
I also wrote about how railways sit on the same construction as Roman roads, but with the benefits of smooth, low-friction running. And I wonder what the Empire would have looked like if they had railways. Not even steam railways, but just horse-drawn railcars that could pull literal tons of material. Would they have expanded their road-building empire with rail as the supply line? Which Roman emperor would have been the first to invade with rail-drawn weapons?
But Roman roads don’t really analogize to the sprawling suburban streets of America and other car-obsessed places. For a question about the costs of road vs rail, I wrote that the way freeways are built is still more-or-less recognizable from the Roman approach: dig down and remove soil, add different layers of material, put a smooth-ish surface on top. But today’s suburban and residential asphalt roads are explicitly a product of the availability of cost-cutting technology, where asphalt can basically be laid atop the natural soil.
Extremely fascinating comment of your’s in the link!
I also wrote about how railways sit on the same construction as Roman roads, but with the benefits of smooth, low-friction running. And I wonder what the Empire would have looked like if they had railways. Not even steam railways, but just horse-drawn railcars that could pull literal tons of material. Would they have expanded their road-building empire with rail as the supply line? Which Roman emperor would have been the first to invade with rail-drawn weapons?
It’s always fascinating what small things make such massive differences. To think that wooden railways only date to the 16th century AD, but are such a simple idea. A matter of someone having an idea, rather than a restriction of material technologies available.
It’s always fascinating what small things make such massive differences. To think that wooden railways only date to the 16th century AD, but are such a simple idea. A matter of someone having an idea, rather than a restriction of material technologies available.
I mean, there’s that, and also this person having the resources and motivation to bother. Even the Romans built roads for partially ideological reasons, and built them either overly straight or overly wide as a result. Which means reworking the entire system, to force wagon standardisation on everyone in the empire, to slightly improve hauling efficiency, was not going to be on the agenda. The way you worded that makes me think you know they also had stone rails in certain places already.
If you look just at ideas and technologies which have immediate applications to a large number of people, you tend to find they’re invented over and over again, regardless of how weird. Pottery, agriculture, and metalworking are a few ancient examples that come to mind. More recently, any number of technical things got invented once on each side of the iron curtain.
From that perspective, I could speculate that Europe might have invented/perfected/popularised rails, because they were building big, private coal mines, because they cut down all the trees over the span of the Medieval period.
to force wagon standardisation on everyone in the empire, to slightly improve hauling efficiency, was not going to be on the agenda
There remains some debate whether the modern railway and and motor vehicle gauges (ie distance between wheels) are direct descendents from the spacing between wagon wheels of the Roman Empire era, usually coming up in response to the nonsensical claim that NASA space shuttle dimensions were restricted by the rail gauge of a tunnel in the Rocky Mountains, due to descending from really old wagon gauges.
But of that debate, one aspect which I find highly plausible is that the earliest wagons would have been built to approximately the same gauge, even though each one would have to be constructed by hand independently. The reason would be for handling, because on smooth ground the gauge doesn’t matter. But on rutted roads, it would be awful to have alternating left and right wheels continually falling into the ruts.
A better situation would be to fit into both the ruts on left and right, then remain there until having to make a turn. Given that wooden wagons and wooden wheels weren’t exactly the most durable of that era, anything to make them last longer would be sensible, I would think.
With regards to wheels specifically, wood wheels are great for loads that are perfectly down the spokes. But the moment a sideways force exists – such as sliding into a rut – the wheel is put into tension along the axle, which is not great. At the very minimum, the (likely) journal bearings would be deeply unhappy. In the worst case, the outside of the wheel (the “tread”, so to speak) could be ripped off, taking the spokes with them and collapsing the entire axle. In the modern day, rarely does anyone have experience with wheel failure but it would be fairly catastrophic.
I might have too much to say about modern wheels, specifically spoked bicycle wheels and pneumatic tires, which are an engineering pinnacle.
Your bicycle tire writeup was fascinating! Thanks for that
I remember many years ago, I rode on a steam train, and there was a big lecture on the theorised connection to Roman wagon sizes. I might have been the only person listening who wasn’t bored.
Given that wooden wagons and wooden wheels weren’t exactly the most durable of that era
Do you know if they were they were using wheelwrighting like what you’d see in later Europe, or something more basic? I know barrel making, which has similarities, was a thing that really caught on towards the end of the Empire.
I will admit that my pre-1800s wheel knowledge is quite limited, but one thing which is clear from wood as a building material is that it’s mostly used for its compressive strength. That is, the spokes of a wooden wheel are there to only bear weight when directly below the axle. Otherwise, they’re not doing too much.
Some wood wheels do have massively thick spokes which can singularly bear the entire weight from the hub, as the wheel rotates. This makes the rim less important, apart from providing a smooth surface to meet the road.
But other wood wheel designs used a massively thick rim which would hold the circular shape. These designs meant the downward force was spread across multiple spokes (not just the immediate bottom one) and so each spoke could be slightly narrower.
The big innovation with bicycle wheels circa later 1800s is that the spokes are in tension, not compression. And that simultaneously makes the rim into a natural circle while saving rim weight, plus it distributes the load forces across all the spokes, making them all thinner. Add the fact that steel has incredible tensile strength and the result is pencil-thin wires supporting over 100 kg easily. Since material science has blessed us with materials with more tensile strength than compressive stength, this is almost as optimal as it gets, for a wheel with purely vertical loads (near-perfect for bicycles; not as good for automobiles).
The simplest intuitive understanding is to imagine what happens if a bicycle wheel tried to deform at the bottom. If so, three or four spokes will be relieved of tension, but some 30 spokes other would undergo extra tension. And that would work to resist the deformation, returning back to the intended circular shape. Wood wheels have no such restorative feedback loop. Nor can wood wheels spread out an overstress to multiple spokes, and instead would probably collapse the wheel with attendant injuries.
The drawback of the wire spoke wheel is that as the diameter gets larger, the transverse strength will diminish, because the spoke angle from the rim approaches 90 degrees. That is to say, if a bicycle were doing a power-slide, a really tall wheel would run the risk of “dishing” out, where the rim basically slides off-plane from the hub, turning into something like a cone, potentially catastrophically. Old timey penny-farthing bicycles are at the diameter where this is a problem, but fortunately those bikes can’t practically be slid sideways. This is also why cars moved away from spoked wheels, because of this lack of lateral strength.
The other drawback is that the structure is the most efficient (read: saves the most material/weight) when the rim is narrow. But if being paired with a wide tire, then the rim has to be wider and that costs material. Bicycles use “balloon tires” that expand wider than the rim, and those have worked great for even MTB bikes that need the extra tire width. But today’s fatbikes and e-bikes with >4 inch (100 mm) tire widths necessarily require wide rims, and that’s taking efficiency off the table. It’s another reason cars (which need tire width bc they’re so heavy) moved away from spoked wheels.
As for the parallel with barrel making, I think the cooper uses steel/iron bands to bind the barrel together, right? I think I’ve seen steel along the tread of wood wheels, but I don’t know if that’s structural to the wheel or if it’s more like tread to prevent the road from destroying the rim surface.
but one thing which is clear from wood as a building material is that it’s mostly used for its compressive strength
Well, the wood of the spokes, which is usually chosen to be something like oak for that reason. That’s a nitpick, though, because you clearly understand the rim and hub experience more complex forces.
Since material science has blessed us with materials with more tensile strength than compressive stength
The fascinating thing is that if you use really basic materials, that’s not exactly true! With a few ultra-modern exceptions, ceramics can’t tolerate much tension. Wood can a bit, and so was even used by the Inuit for tools, despite their total lack of access directly to it. But, it has has a few other weaknesses, like anisotropic strength, anisotropic shrinkage that doesn’t even follow sane, straight lines, softness, a grain of appreciable size and lack of heat resistance. Natural cordage has great tensile strength, but ~zero compressive strength and will stretch to laxity over time. There’s similar stories for things like hide, sinew and cloth. Finally, bone lands somewhere in between ceramics and wood, and can be hard to find large pieces of depending on available fauna.
It had huge impact on the history of how machines developed. And it was the whole reason metal found great use even in the days when it was extremely, extremely precious. Tin is a critical ingredient in historical bronze, and it’s actually about as abundant as a precious metal. Arsenic was also available for that, but it was so toxic they didn’t even want to expose their slaves, and so the Near East moved over time to tin. In other metalworking societies they rapidly moved to much more difficult metals and/or made do with the limitations of stone-age tools, maybe due to even less abundant tin.
I think I’ve seen steel along the tread of wood wheels, but I don’t know if that’s structural to the wheel or if it’s more like tread to prevent the road from destroying the rim surface.
It’s structural. I suppose you could turn a wood ring out of one big log, and if you did it along the tree’s axis it wouldn’t shrink or grow into an oval, but it would be tricky to get the spokes in, and tricky to get (and keep! seasoned wood can still swell or shrink as humidity changes) it all tightly in contact. In reality, the rim in in pieces. IIRC they’re steam-bent, with the grain running along the axial direction, and made of something like yew that responds well to flexing.
The origin of the word tyre is that metal band. It’s put on hot, and the compression as it quenches is what holds the entire assembly together. Earlier wheels weren’t necessarily the same. At least some ancient Egyptian chariot wheels used sinew as the compressing element, and it sounds like it may have been in a different place.
Which means reworking the entire system, to force wagon standardisation on everyone in the empire, to slightly improve hauling efficiency, was not going to be on the agenda.
I mean, the invention of wooden rail systems just for mining would have, itself, been a massive improvement in the already incredibly-OP realm of Roman industry, whose annual metal output outpaced that of all of Europe until the industrial era.
I agree that revamping the road system of the Empire would not have been on any immediate agenda, since Roman roads were largely constructed to facilitate foot traffic, not hauling.
Do we know how much tonnage a given Roman mine would actually produce per day? With soft coal, you can excavate it very fast with simple tools. I’m wondering if hauling ore and spoil out was actually not that much of a bottleneck in a typical underground mine.
I don’t know that we have any numbers on coal, which was only lightly exploited in the Roman era. I think there are some estimated numbers on gold, silver, and iron mines, but it’s been a while since I’ve read up on Roman metallurgy, tbqh.
Yes, I meant they didn’t do much coal, so they wouldn’t have had the problems big coal mines presented in later history.
If you have enough wood around I imagine there’s not much reason to bother with the hazards, expense and relative unpleasantness of the finished product. Other ancient cultures bothered relatively little with coal too AFAIK, although I might be missing some exception.
A matter of someone having an idea, rather than a restriction of material technologies available.
For this, I look to sci-fi. And dang, now I wonder if the Romans had their own body of sci-fi, and if any of it was accurate in terms of things the Roman Empire – unless it hasn’t actually died yet!!! – would never live to see.
For this, I look to sci-fi. And dang, now I wonder if the Romans had their own body of sci-fi, and if any of it was accurate in terms of things the Roman Empire – unless it hasn’t actually died yet!!! – would never live to see.
Oh boy, do I have a treat for you.
https://en.wikipedia.org/wiki/A_True_Story
We have yet to create giant insect chimeras for our cavalry or devised a way to plant our testicles to grow into an all-male population, but we have traveled to the moon on a ship, viewed the Earth below from a magnifying screen, and invented gay marriage!
I would read this alt-history.
It’s also worth pointing out that asphalt is one of the most recycled materials on earth. That’s admirable. Recycling and repaving produce a lot of toxic gasses and particulates, though. It’s specifically mixing the asphalt with tar that gets nasty.
See also: the lightbulb conspiracy
Run cargo trucks at highway speed over Roman roads and see how well they hold up.
Heavier vehicles do dramatically more road damage than light ones, and a horse cart weighs a while lot less than even a compact car.
Roman road construction isn’t some ancient lost secret that cannot be recreated, it just isn’t fit for modern purpose.
So my sister is a civil engineer. I asked her: „The damage a vehicle does to the road doesn’t increase linearly with the weight, right? It’s quadratic.“
„Oh no“, she replied „it’s to the sixteenth power.“
Oh god. That’s a rare fucking power to see.
Is that tire pressure (on the pavement), total vehicle weight, or axle weight?
I’m sorry, I don’t know. I’m not the civil engineer.
If you asked her sometime, I’d be very appreciative.
Ok, she issued a correction.
It’s the axle weight to the power of 4.
Ah. That’s still uncommonly high though. I see why they say trucks do almost all of the damage.
Looks like it’s axle load, and damage is measured by time for the road to become unacceptably broken by whatever standard.
Run cargo trucks at highway speed over Roman roads and see how well they hold up.
I’m pretty sure modern traffic does use Roman roads, although extreme grades and an uneven surface limits the possible speeds. This meme is saying the opposite thing, which is that Roman roads were overengineered.
and a horse cart weighs a while lot less than even a compact car.
I question that, even. Juvinal’s cart loaded with Ligurian marble would have weighed a damn lot.
