Moving from car ownership to Zipcar does introduce other burdens, though, especially around scheduling. You have to make a reservation in advance -- in my neighborhood, a couple days in advance for peak times -- and you can't cancel beyond a certain time. You have to know exactly how long you'll be and your plans can't really change, and if you get stuck in traffic, you get to pay an extra $50 for being 5 minutes late. It's a great service for what it is, but it's not for everybody.