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Comment by azalemeth | Hacker News Reader

A fun little fact is that the load on a road causes damage roughly proportional to the fourth power of its mass – or at least, proportional to the fourth power of the weight of each axel. The US government publication detailing this is here – https://onlinepubs.trb.org/Onlinepubs/sr/sr61g/61g.pdf – in 1962 – and it's become something of a famous approximation ever since.

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That'd mean that a twice as heavy vehicle would cause 16 times more damage than the lighter one. Wild and not really intuitive!

And relevant for public policy, as both SUVs and EVs (including EV SUVs) become more common on roads.

Or not, because the axle weight of semi trucks are much higher than EVs, and due to the fourth power effect, essentially all road damage is caused by trucks.

But semi truck road usage is generally limited to certain kinds of roads and isn't broadly increasing.

My point is that the effect of non-large vehicles getting heavier is magnified beyond what people might realize.

Trucks basically do all of the damage. Generally they can have 16,000 lbs per axle. With 5 passengers, a Model X weighs 6000 lbs and has 2 axles. 16000/3000=2.66. 5.33^4=807, plus the truck has 2.5x as many axles, so the semi is doing 2017x as much damage as the car.

Even in residential areas, package delivery trucks are always driving around, and they often have about 15000 lbs/axle, so they're doing about 625x the damage of a Tesla X. Road damage due to passenger vehicles is just not significant, even if they're heavy for a passenger vehicle.

Don't worry, us taxpayers will cover the damage.

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