Check out this video of Vauban in Germany. They went completely without cars.
When I think about it, here in the northeast we could do that very easily. For example within walking distance of me I have schools, markets, malls, restaurants, bookstores, pretty much everything I need as an urban dweller.
I’d like to see us take the Federal Hill/West End neighborhoods and make them bike only. I can see elements of this creeping into re-designs of roadways of the city where there will be dedicated bike lanes as well as shared lanes, etc. But Take my area, it’s bounded on one side by Westminster St., and on the other by Atwells Ave.
Here’s the google map. Areas in blue are bicycle or public transit only. No cars.
Areas in green are shared by public transit, bicycles and cars.
A good start if you ask me.
Spewing Truth in the face of Lies 
Broadway alone is one of the city’s busiest transit lines, and probably the only section that runs in a straight line. Making it part of a pedestrian only zone would be disastrous for the entire system. The West Side actually functions very well as a mixed use zone already. If I were going to try this anywhere, it would be Elmhurst/PC.