I'm thinking we'd calculate the average cost for driving a car based on a set of metrics (curb weight, miles driven, etc), then apply discounts for certain cars (older cars, EVs, etc). The bulk of the impact would be on large trucks and wealthy people. That would increase costs for shipped products (and encourage local production), which would be balanced out by better mass transit.

It should certainly be phased in to avoid a big shock, but that should be the goal. It turns out that driving for me is cheaper than taking transit because roads are so heavily subsidized. If I had to pay for my actual use, transit would look a lot more attractive.