If the tax is on the Fuel, everyone will pay equally for their pollution.
You are correct that an older car could pollute more than a Prius, even if driven for less miles, but in my solution they would pay more, because the tax is on the Fuel.
What I am against is taxing based on a vehicles ability to pollute. As the same argument works the other way, you could have a Prius and drive 60k miles (at 40mpg) a year which would be far more polluting than my old gas gussler which is only drven 2k miles (at 10mpg) a year. But in most countries the gas gussler will be taxed more because it has the ability to pollute more.
But having the ability to do something doesn't mean that it will. Most cars have the ability to break the speed limit, but they don't go around giving everyone speeding tickets.
Anyway, rant over, I'm not in charge... But hopefully if I pester enough people they might start to listen.
Ah, I didn't see that you were outside of the US, and thus misunderstood where you were coming from. Here, any other fees or taxes on a car aren't based upon the ability to pollute. They are on vehicle type or property value.
Taxes should be based on vehicle weight which is what damages road surfaces and fuel consumption, two variables and two taxes. Weight tax would be part of the annual licensing of the vehicle, consumption on pump purchases per gallon as we have now. Then, and most importantly, a stipulation in the law forbidding the criminals, uh I mean politicians, from robbing the fund for their pork projects. All funds must go to highway infrastructure.
The annual Road tax here is based on fuel consumption, or C02 which is directly linked anyway. Good idea in theory, however as you know, the fuel tests are flawed anyway, with most cars using way more fuel, and therefore emitting way more pollution than the figures suggest.