My wife and I have adopted this approach.  We recently  purchased a 1991 GM Metro (40 mpg/city). We still own a 1995 Ford Ranger p/u, but now rarely drive it.  Both of us walk to work, so our mileage is quite low.  And it is quite shocking to drive any distance in the traffic prevalent in our area (Sacramento, California).  People are so stressed on the roads and many drive like complete maniacs.
I have thought a lot about this sort of thing, since if I were honest, I would shut myself down pretty soon since I can't twist my neck much anymore and am getting almost as slow as the nuts I have to dodge when I go into town in my little dirt road.  What seems to me is the right solution is the car club, in which everybody has access to any car they might want at any time via cell phone, so a central computer knows everything necessary, and if I want to go , I just hit the button and bingo! a car of the right kind (econobug, bus, rusty pickup, muscle rocket, etc) shows up and takes me, or lets me take it.

This way, I pay just for what I use, and somebody else more competent is doing the nightdriving, fixing the flat battery, the headlight, the skizzy computer and all that.   I had a student who did a great job simulating this, and what he showed was an amazing saving in everything- money, parking space, total time devoted to transport, home space utilization, and the works. Average time delay was 7 minutes.  So? You call ahead of need.

By the way, I tried to sell this idea locally (many times) and the people who like it the most are young mothers and Quakers, and the ones who call me a commie trying to rob them of their hash and sex are young men.