A lot of people on here are big on just eliminating or drastically reducing parking in cities. That works fine if you live and work downtown and don't need a car otherwise. But I pretty much guarantee you that the vibrancy of your downtown is sustained to a large degree by people who don't live there coming in. I was just in the local city for dinner and a play last night. I can guarantee you that, to the degree traffic and parking make that too much of a chore (and, believe me, it's getting there) I'll just fire up a movie at home instead.

ADDED: Some cities (e.g. New York, London, various other European cores don't really lend themselves to driving in--though many people still do in the evenings--but that presupposes public transit that can comfortably substitute for driving in terms of convenience and cost).