I don't have an answer, but in thinking about it, I'm realizing that living where a car is necessary is not only poor planning for the planet, it's poor planning for our personal future.
I honestly don't expect my Florida home to be above water by the time I'm no longer able to drive. Even so, as a healthy middle-aged adult it would be very easy to forego a car here. But if and when my eyesight, reflexes and/or judgment no longer allow me to drive a car, I won't be able to ride a bicycle here safely either, and public transit is minimal. Where we live in Ohio it would be EXTREMELY difficult to go without a car, and it would definitely require a high level of physical and mental fitness.
So... can we take this thread in a slightly different direction? Who lives someplace, or knows of a place, with good public transit and access to a variety of physical necessities, arts, services and social activities, where someone could live without a motor vehicle, without being terribly isolated and deprived? WHERE will we go when we stop driving?
I nominate D.C. off DuPont Circle where my grandmother lived for several years. (Just a few miles from the house where she'd lived for decades.) It always seemed like a terrific place to live at any age. Where else?