@ Tom, read "has to happen" as a moral imperative rather than a practical one. Of course the phrasing is an exaggeration, we humans are free to ignore all evidence and even accelerate our march to making the planet uninhabitable. some would describe such behavior as self-destructive, but we are free to do it nonetheless. Likewise we are free to ignore the fact that by buying so much oil, we are funding the terrorists and extremists that serve as the justification for our multiple wars in far away places. There are other more practical arguments as well, like the fact that a 10 minute commute by bicycle or bus is a vast improvement in quality of life over an hour of stress-filled traffic in the choked urban arteries. Taking steps to reduce personal motor vehicle traffic (increase tax on gas, introduce tolls and require permits for circulation and parking in urban areas, car-ownership tax, reinvesting proceeds to make public transport more efficient, comfortable and accessible by price and location...)is a win for everyone.
@orathaic: you are such an idealist. Bravo! I don't know about a sudden and radical break from motor-vehicle traffic, but there are practical ways to make a transition gradually and keep motor-free the goal toward which we should always strive.
Maybe it's obvious, but another consideration is the distribution of retailers/outlets. In the US, the dominant model is to have a few massive stores around the peripheral of a city rather than many more distributed shops that people can access easily walking. In Madrid, I go shopping once a week for a family of three. I walk to the market with a couple hand-carts and walk back. We have markets in each neighborhood with stalls where smaller sellers can sell specialty and local foods, fresh fish, butchers, fresh fruit and veg of very high quality. These markets I believe are run by the city but paid for in rent to the sellers. Additionally, there are small groceries well distributed.