https://www.insidescience.org/news/how-much-damage-do-heavy-trucks-do-our-roads https://www.insidescience.org/news/how-much-damage-do-heavy-... > The fourth po

https://www.insidescience.org/news/how-much-damage-do-heavy-trucks-do-our-roads https://www.insidescience.org/news/how-much-damage-do-heavy-... > The fourth power law (also known as the fourth power rule) states that the greater the axle load of a vehicle, the stress on the road caused by the motor vehicle increases in proportion to the fourth power of the axle load. https://en.wikipedia.org/wiki/Fourth_power_law https://en.wikipedia.org/wiki/Fourth_power_law tl;dr vehicles with higher axle loading do significantly more damage to roads, scaling with the 4th power. Meaning the vast majority of standard wear and tear on our roads is going to be from heavy trucks, not passenger cars. It makes sense to scale usage taxes in a similar way.