Hacker News Reader

Comment by ramblenode | Hacker News Reader

I'm not an economist or a historian but I wonder if there is an aspect to Roman wealth here that isn't captured well by GDP. As an example, Roman roads are famous for their durability, whereas modern highways (which experience very different traffic) need to be repaved on the order of years or decades. For the same distance of road, it would seem a great deal more economic activity in the form of labor, construction, and materials is needed to sustain a modern roadway. If key Roman infrastructure investments simply had a longer lifetime than modern infrastructure (because of design, requirements, etc.), wouldn't that imply the per capita wealth of the empire could be high without a particularly high GDP? Curious if there is any literature about this.

View on HN

A very important aspect to consider here is that a roman road did not have 100 000+ multi-ton vehicles traveling on them per day. The reason roman roads lasted long is that the load on a road with only manual labor traffic is a thousand times less than that of a modern highway.

Old roads in Europe that are subject to truck and car traffic crumble very quickly unless meticulously maintained.

And even then, most road degradation is due to heavy trucks. Cars contribute very little.

http://facweb.knowlton.ohio-state.edu/pviton/courses2/crp776...

Skip to page 4, where it covers ESAL. A standard trailer is expected to do around 800-1000 times the damage of a standard passenger car. The conclusion:

"When discussing road wear cars don't matter: road damage is effectively caused by trucks."

> road damage is effectively caused by trucks.

So, if road use is charged by a steeply progressive schedule, and driver cost is not an issue, will we see fleets of light autonomous trucks replace the heavyweights?

No, because the weight is the cargo. As more and more semi-truck trailer beds transition to aluminum floor joists, for weight reduction, it's an overall increase in productivity because the truck can now haul more cargo weight.

TBF, I suspect GP is referring to reducing the gross weight of trucks (vehicle + load), rather than the net of the vehicle alone.

That's possible too, but would be tremendously less efficient as you'd have the same air resistence (or at least a substantial amount) but without the same cargo capacity.

Railroads tend not to develop potholes.

You can't really reduce the net weight whilst carrying gross weight beyond a point because the structure won't cope with holding the cargo. Maybe you can optimise some of it out but whether a human presses pedals/turns wheels or a computer does is relatively immaterial towards the net weight of the vehicle structure. Autonomy won't play a big role in that compared with improved design and materials.

Also, remember that roads aren't made out of head-hardened solid steel - if they were, they'd probably nearly forever.

Rail itself may not get quickly damaged (though they do) however rail wheels, which are made of relatively softer metal, develop all kinds of damage, require the machining away of the damaged surface periodically (as in, wheels shrink over time as mateiral is cut off it to get to new metal below) and only last a matter of years for heavy haul environments: http://www.asa.transport.nsw.gov.au/sites/default/files/asa/...

Search for spalling, shelling and rolling contact fatigue as examples.

It would be fuel vs. road cost ...

(There might be a paper in figuring out the sweet spot given hypothetical costs ...)

However, road damage doesn't scale with the weight. The damage roughly scales like the weight per axle to the power four! e.g. http://www.pavementinteractive.org/equivalent-single-axle-lo...

I figured it would be a power, was just hand-waving with "steeply progressive" ;-)

Most Roman cargo moved on ships. Roads were for unavoidable overland transport, where rivers didn't suffice, and largely involved personal transport or local movements.

Though the Romans didn't make heavy use of them, one of the first major inland cargo transport systems was canal networks. Canals are almost the equivalent of railroads (trading speed for bandwidth), and have the useful property, I realised a while back, of not requiring roadbed maintenance or resurfacing. Canals don't develop potholes, get muddy, or suffer from the carriage of heavy loads.

The canal boom in Europe began proper in the 1500s, though there were some earlier instances.

Canals can silt up requiring dredging.

Yes, but that's not affected by use or vessel weight.

It is. Bigger vessels means more banks erosion. This is an issue now, this may not have been one at a time of animal traction or river barges.

At what speeds?

Perhaps I wasn't explicit enough in the post, but yes I realize this. The point I was trying to make is that whatever the reason (including the purpose of the infrastructure, its usage patterns, its requirements), if a project could satisfy its purpose with fewer resources/less GDP needing to be reinvested over time, then this represents a higher relative return on their investment. GDP, having the dimension of time, wouldn't necessarily reflect their overall wealth, including the uncounted utility from historical investments.

The upfront investment of a Roman road might still be comparable to the lifetime investment of a modern one when you factor the human resource. How many man hours are spent on a mile of road, including building the tools (cement truck, bulldozer, etc) now versus the mass manual labor required then.

There are several elements of Roman wealth which aren't captured by GDP (or alternatively, of the overreporting of modern wealth by GDP).

One element is infrastructure depreciation. As you note, the materials and construction of Rome tended to last. Stone and Roman concrete both in particular don't degrade with time (though they may suffer earthquake damage). Things built tended to remain built over timescales we are not familiar with, at the very least, centuries rather than decades. Depreciation expense was far less.

Another factor was a much smaller natural capital expense. Not an entirely absent one, and there were problems with deforestation, salinisation, and cropland depletion throughout the Roman empire, as well as hazards introduced by commerce of plague and disease. But the major capital depletion of the modern world, the draw-down of fossil-fuel reserves at rates millions of times greater than their formation, was not present, nor various consequences of such actions, including of course, greenhouse-gas induced global warming and ocean chemistry changes.

(Among the issues Rome did have to deal with was heavy metal pollution, particularly lead and mercury, and particulates emissions. It wasn't all roses. But by relative magnitudes this was a very small fraction of present capital expenditures.)

Vaclav Smil's Energy and Civilization is an epic exploration of the role of energy in history, including the Roman Empire.

https://mitpress.mit.edu/authors/vaclav-smil

We only remember the stuff that actually lasted.

It sounds like you're basically arguing for the use of NDP, net domestic product. Wear on roads et cetera is the cost of the added (design, requirements, etc) of that higher GDP, and NDP would be the net benefit.

GDP is not good measure of wealth, happiness, or greatness of a country. It is useful for the government to increase it when the government taxes income and sales. If everything was made to last forever and we had already produced everything we needed, GDP could be almost zero (food production in US about 2% of GDP?) and the people could be doing great.

Reply on news.ycombinator.com