Per axle. So for instance, if you're comparing an 18-wheeler to a 4-wheel car you have to compare (truck-weight/9)^4 to (car-weight/2)^4. Or ((truck-weight/9)/)car-weight/2))^4
So if a bus was an 18-wheeler, it would be about 16x the wear units, /32 passengers brings it to half.
It doesn't make a difference for the bus you linked, since it's also a 4-wheeler like cars, but if we cared we could add more axles to buses.
But, why don't we do that already? Apparently...
1) regulations don't require it
2) we sort of already do; some buses have rear wheel bogies that have 4 wheels of which 2 are kept raised at lighter weights. Which is basically all the time because regulations don't require it.
3) more wheels reduces fuel efficiency (and costs more money), obviously
4) wheels take up space and reduce passenger capacity, which make the bus less efficient if you don't care about road wear
5) buses have a much more consistent weight load than trucks, since ~30 passengers would be only 3 tonnes of difference.
I'm wildly out of my depth on buses/trucks here, so if a mechanic could chime in on bus/truck weight distribution and wheels that'd be great.
If you add 5 people to the car, call it 80kg per person so your you goto about 2.2 tons, then the damage number would be about ~24, but divided by 5 you end up with 4.8 (so a fully loaded car does about half the damage per person compared to one with a single occupant).
The thing is of course on some level this is large scaling factors applied to small numbers - i.e. tires still don't fail that quickly anyway, neither do roads.
Conversely it is actually weird to see that on this one metric, numerous self driving EV taxis is actually better.
Fuck cars!
A BYD bus weighs 18 tons and carries 32 people including the driver. [2]
A BYD Atto 3[3] carries upto 5 people and weighs 1.8 tons unloaded.
The proportional road wear function of the BYD Atto would be about 10 (1.8^4). For the bus it would be (18^4) 104,976.
So the bus is 10,000 times more wear then the car. Per passenger it's 3000 wear units for the bus versus ~10 for the car.
[1] https://en.m.wikipedia.org/wiki/Fourth_power_law
[2] https://en.m.wikipedia.org/wiki/BYD_K_series
[3] https://ev-database.org/car/1782/BYD-ATTO-3