I don't need a car at all for my job, but i live in a city. It depends heavily on your situation, but if you do live in an urban environment with public transit you could even get away with no cars.
But I just moved back to Washington, and there's no way you could do without a car here. The busses only cover about half the city, and they're few and far between (and they only run until 10pm). I'm 10 minutes away from a grocery store by car, so walking is out of the question. Cities that aren't packed full of people don't have a reason to invest in their public transit systems, because the payoff isn't worth the cost (there's just too much space to cover for so few people).