Fuel taxes already do this, while providing a strong incentive to run smaller and / or more efficient cars.
Roughly, 50% of my fuel bill is on direct taxation. That's it's primary tax cost, not the fixed annual license cost, and gives me a tax bill that's elastic by usage in exactly that way while also promoting efficiency.
Of course, best wishes to anyone trying persuade the average man in the street that this is A Good Thing....
They can turn off their motors without losing any efficiency (which is why hybrids do so well on efficiency in city traffic). Depending on how slowly the traffic moves there will be a point where it is cheaper to stay in traffic (with the motor off x% of the time) compared to paying for parking.
Why the assumption that electricity for vehicular use will be taxed at the same rate as for domestic use when there's wide-scale adoption of electric cars? Red diesel, for agricultural use off-road, certainly isn't taxed at the same level as road use diesel in the UK.
Roughly, 50% of my fuel bill is on direct taxation. That's it's primary tax cost, not the fixed annual license cost, and gives me a tax bill that's elastic by usage in exactly that way while also promoting efficiency.
Of course, best wishes to anyone trying persuade the average man in the street that this is A Good Thing....