What concrete difference will that make?
All I can think of is that it will put more proportional weight onto fuel-efficient cars, which doesn't seem right.
It seems wrong because it
is wrong. Taxing gasoline instead actually provides some measure of incentive to choose a vehicle that doesn't burn through quite as many fossil fuels.
If you want to honestly charge folks for their share of "wear-and-tear," maintenance, etc., well... you're basically going to have to bankrupt the long-distance trucking industry, since they contribute to
so much more road degradation (and a lot of other nasty things) than smaller vehicles, but don't pay commensurately more. And if you care about "congestion"*, the right answer is, counterintuitively but surely, to stop building new roads, and in fact
take space away from cars and give it to more fundamentally efficient uses of the road space like buses and bikes. People do have to get from point A to point B... but forcing them to do so in a car is the real problem here, and taking ever more space to build wider and more far-flung highways (making point A and B ludicrously far away from each other) just deepens that forcing effect and makes it worse. Induced demand is hard for folks to wrap their heads around, but it has been proven time and time again.
*(In the cores of larger metros, some sort of cordon charge with the proceeds going to fund mass transit is indeed called for. In smaller metros, oftentimes "congestion" just never gets bad enough. Congestion in the peripheries is... a horrifying spectacle that I'd be happy to rant about but right now will just say won't get solved by either a VMT or just building more roads that's for sure)
