Our cars are driven a total of under 4000 miles per year. For me,its not because of an environment conecern, but obstruct being stuck in traffic. I bike to work but if I ever need to go during late evening when there is little traffic then I always use the car as I get there and back a lot quicker.
Also for errands and groceries etc,I always use the car as I can get things done quicker (on weekends). I thought of using the bike, but it makes no sense for me.