>use-taxes are incredibly effective methods of placing the cost with usage of a shared resource. But road wear simply is not proportional to gas use. If you do

>use-taxes are incredibly effective methods of placing the cost with usage of a shared resource. But road wear simply is not proportional to gas use. If you double a vehicle's weight, its gas usage will almost certainly less than double (this depends somewhat on driving patterns, but air resistance is generally a significant factor in mileage), while the road wear it causes will increase by roughly a factor of 8. A flat tax on gas can't possibly internalize the costs of road wear, though it could internalize the costs of CO2 emissions, which are actually proportional to use.