Tax people based on mileage, not on engine emissions.
We already have a near perfect environmental tax on burning fuel in this country....our heavy rates of fuel duty. This perfectly taxes someone as mileage, economy and therefore overall emissions are a direct result of fuel consumed. If anything, VED should be scrapped and this should all simply be loaded into fuel duty for a perfectly "fair" system (although lets not go down the rabbit hole of EVs with their near zero tax rate, who knows what will happen to these).