[dragontamer]

I have to imagine that if Car X wore out 5kg of rubber, that it would have had half the impact of another Car Y that wore out 10kg of rubber.

Right? Tire wear has to be directly correlated to road wear. They're in physical contact with each other after all, so it'd be as direct a measurement as any other possible methodology.

[positr0n]

But rubber does not damage concrete, it's the weight of the vehicle that damages the concrete.

As an extreme example, if I floor a 2000lb Miata when the light turns green that will deposit a ton of rubber on the road. But that does nothing compared to just driving through the intersection in a 6000lb suburban.

[dragontamer]

I'm not saying "rubber damages concrete" any more than current gas taxes say "gasoline damages concrete".

I'm saying the degregation of rubber is (likely) in direct correlation to the amount of road damage. (Much like gasoline is in direct correlation to miles-traveled, and thus is also an indirect measurement of road damage)

There's no need for causation in this discussion. Correlation is enough to be worthy of a good tax design.

[chongli]

Yeah. It's the vehicle weight combined with temperature fluctuations and water, ice, and salt. The worst case scenario is when the road develops tiny cracks that fill up with water and then the temperature drops, causing the water to freeze and expand inside those cracks. The cracks grow larger and then when the water thaws and evaporates it leaves behind those large cracks/voids which heavy vehicles collapse due to their weight, turning cracks into potholes.