Here's a puzzle, or something to acknowledge. I walk to work, my husband walks to work. We have one car, which we often leave undriven for days at a clip. And yet, the odometer reads more than 70,000 miles, (we got the car in November of  2006, so that makes it about 3 1/2 years old, which means we drive at least 20,000 miles a year.
Mostly to places where we then WALK!!  In some ways, that's insane.  I can not pride myself on my eco-ness or my greenology having only one car, because I use that car a lot, for my own amusement, not even to get to work.   So everytime I wonder why we, as a society, can't do more with mass transit and giving up driving, I have no further to look than my own odometer.  Yikes.