It reminds me a bit of garbage collection in Amsterdam; lots of cities try to let people pay for the amount of trash they produce, but Amsterdam will let people thrown away their trash for free, and be happy they throw it away properly, because taxing that is going to create a mess.
Taxing gas is probably the easiest way to do it. Heavier cars probably use more gas than lighter ones, right? Except EVs don't use gas at all and still use the roads. There's just no easy solution.
It’s usually the lower middle class population that gets shafted, and bizarrely the activists among them keep fighting for the government to impose more taxes.
The rich will figure out a way to make these taxes not apply to them, just like how many take advantage of expensive new EV subsidies, solar generation subsidies, or property taxes.
And people wonder why the middle class keeps on getting smaller.
Ideally it's related to the wear and tear the vehicle places on the road. That's a function of distance. But also weight and axle count.