Being car free has less of an impact on environment than most people want to believe. I you are like most Americans, your house generates several times as much Co2 as your car does.
I can afford a car, I have a drivers license, and I have a place to park a car (a rare thing in Tokyo), but I don't need a car. I'm fortunate to live near a subway/JR station, and Tokyo Station is only 15 minutes walk. In between there are pretty much all the shops I need for necessities.
A few years ago things were different. I lived outside the metro area, and my workplace was more than 30 kilometers from my house. I had a car, but I usually rode my bike. I would do my commute in the morning, and then in the afternoon I would add a little to it, so I often rode as many as 100 kilometers a day. I didn't do it to save money or reduce Co2, I did it simply because I enjoyed riding.
I still enjoy riding, and I've just returned from a 30 kilometer shopping trip to Shinjuku and back.