I grew up in Newton, MA and you can live there without owning a car or knowing how to drive. The city is broken down into about a dozen villages and there is a shopping center area for each village so you're never more than a mile away from shopping. They have five rail stops and several bus lines. There are some main roads that are very busy and not great for cyclists but they have sidewalks on both sides of the road so good for pedestrians. So you can design cities to be walkable but it seems to be very hard to retrofit.