Aother interesting thing about roads is that they’re build to withstand the wear and tear from heavy vehicles.
This doesn’t seem interesting, until you also find out that the wear from all other vehicles is completely and utterly negligible. Doesn’t matter if you ride a bike, a motorcycle, car, electric car, pickup or SUV. None of the personal vehicles make a dent on the roads of any meaningful size, even if they make up a majority of the traffic.
Obviously we still need the roads for small vehicles, but the cost of constant maintenance all comes from cargo and busses.
If you see it this way, then almost all road construction is a hidden subsidy for the cargo industry who uses trucks instead rails or boats.
It would make a lot of economic sense for the society as a whole to demand fewer cargo trucks and more cargo rails.
Huge heavy SUVs and large trucks absolutely do cause wear and tear, and EVs are especially heavy. The surface layers of roads are damaged over time by vehicles if the foundation of the road mostly remains unimpacted.
Sure, the Hummer itself is already 16 times worse than a regular 1 ton car, but in the scale of things, the difference between any personal vehicle and a truck is about the same as whatever the truck is.
The fourth power law applies to weight per axle, assuming identical axles/tires. In reality, the typical tandem axle arrangement on big trucks (18 wheels across 5 axles, the four back axles paired together as tandems) spreads the load over a much larger road surface area than a typical 4-wheel passenger vehicle.
Civil engineers have models and formulas for that, and there is indeed much more road deformation from the heavy trucks, but it’s probably closer to thousands of times the load for an 18-wheel tractor trailer than for a passenger vehicle, not 500,000. Note in that analysis, it talks about which power to use (not always 4) for different types of road wear or damage, and many of them are less sensitive or more sensitive to vehicle load.
It’s all interesting stuff, but I worry that people on the internet have put way too much value on the fourth power law here, stretching it beyond the original scope or overstating its applicability to practical road design issues.
I don’t think most of the wear and tear on roads actually comes from the weight of vehicles driving on it, though.
In most places where I’ve lived, the cracks and potholes are caused by the shifting of the ground underneath, freeze/thaw cycles of water/precipitation, and things like that. Most roads would still require maintenance to keep them driveable, even without vehicles driving over them.
It becomes obvious with dedicated bike trails or protected bike lanes, where motor vehicles simply do not have access to those stretches of pavement, where potholes can still form over time.
Aother interesting thing about roads is that they’re build to withstand the wear and tear from heavy vehicles.
This doesn’t seem interesting, until you also find out that the wear from all other vehicles is completely and utterly negligible. Doesn’t matter if you ride a bike, a motorcycle, car, electric car, pickup or SUV. None of the personal vehicles make a dent on the roads of any meaningful size, even if they make up a majority of the traffic.
Obviously we still need the roads for small vehicles, but the cost of constant maintenance all comes from cargo and busses.
If you see it this way, then almost all road construction is a hidden subsidy for the cargo industry who uses trucks instead rails or boats.
It would make a lot of economic sense for the society as a whole to demand fewer cargo trucks and more cargo rails.
Huge heavy SUVs and large trucks absolutely do cause wear and tear, and EVs are especially heavy. The surface layers of roads are damaged over time by vehicles if the foundation of the road mostly remains unimpacted.
While big cars do more damage than small cars or a bike. It’s seriously negligable compared to any sort of goods transport vehicle
The weight of a heavy electric Hummer is 4.5 metric tonnes.
The maximum allowed weight of a fully loaded cargo truck is 44 metric tonnes.
According to the fourth power law, this would make the impact of the truck more than 500 000 that of the Hummer.
https://en.wikipedia.org/wiki/Fourth_power_law
Sure, the Hummer itself is already 16 times worse than a regular 1 ton car, but in the scale of things, the difference between any personal vehicle and a truck is about the same as whatever the truck is.
The fourth power law applies to weight per axle, assuming identical axles/tires. In reality, the typical tandem axle arrangement on big trucks (18 wheels across 5 axles, the four back axles paired together as tandems) spreads the load over a much larger road surface area than a typical 4-wheel passenger vehicle.
Also, the models themselves aren’t that robust. It’s from a single comprehensive study of loaded trucks, from 1958-1960, that has been very influential, but the tests itself never went down to passenger car weight.
Civil engineers have models and formulas for that, and there is indeed much more road deformation from the heavy trucks, but it’s probably closer to thousands of times the load for an 18-wheel tractor trailer than for a passenger vehicle, not 500,000. Note in that analysis, it talks about which power to use (not always 4) for different types of road wear or damage, and many of them are less sensitive or more sensitive to vehicle load.
It’s all interesting stuff, but I worry that people on the internet have put way too much value on the fourth power law here, stretching it beyond the original scope or overstating its applicability to practical road design issues.
I don’t think most of the wear and tear on roads actually comes from the weight of vehicles driving on it, though.
In most places where I’ve lived, the cracks and potholes are caused by the shifting of the ground underneath, freeze/thaw cycles of water/precipitation, and things like that. Most roads would still require maintenance to keep them driveable, even without vehicles driving over them.
It becomes obvious with dedicated bike trails or protected bike lanes, where motor vehicles simply do not have access to those stretches of pavement, where potholes can still form over time.