The tax should be based on vehicle weight too. Given two cars with the same fuel efficiency, the heavier one should be paying a higher tax still, cube law propo

The tax should be based on vehicle weight too. Given two cars with the same fuel efficiency, the heavier one should be paying a higher tax still, cube law proportional. Double the weight? Road tax is 8x. Especially in the US we need stronger discouragement to buying larger vehicles, and since the damage a vehicle does is proportional to the cube of it's weight, we kind of get two birds with one stone.