It's not quadratic or cubic: it's the fourth power. Somewhat mitigated by large vehicles having more axles, but each of those axles counts. So if a 40 tonne l

It's not quadratic or cubic: it's the fourth power. Somewhat mitigated by large vehicles having more axles, but each of those axles counts. So if a 40 tonne lorry has 5 axles, the vehicle does (5/2 * (40/5)^4/(2/2)^4) = 10240 times the damage of a big car weighing 2 tonnes, and 163840 times the damage of a car weighing 1 tonne. Which, does mean that the vast majority of road wear is down to heavy vehicles. But it does also means an SUV or a Tesla (2 tonnes) causes 16 times the damage of a Micra (1 tonne).