The unsolvable problem is building a nice walkable city in which a very high proportion of driving age adults have a car. They just aren't compatible. You have to create a place where nobody really "needs" them and not everybody wants them.
Sure even your favorite walkable cities have too many cars (most of them), but the number of locals who own them is quite small (Manhattan: 22% of households, Paris (all) 1/3, etc...).
Happy to be wrong, but I'd bet the brain geniuses in the linked article below believe they can solve this problem.
For some of their couch quarters and some junkets I will explain this to them as we tour the world with examples.
