> I prefer a ban, as it's fairer to everyone. There are externalities that are very difficult to price (pollution, accident risk)

That's a fair argument. I think a car-less future for urban centers is a good goal, but you need a huge transit infrastructure that I don't think most (any?) cities have right now to support it. Permitting is a transitional tool to enable a gradual phase out while letting the polluters/accident-causers etc. pay for the costs they're putting on the rest of us.