Surely somewhere in that more-than-half-of-all-car-trips there are a few examples of car errands that could be easily replaced by bike, scooter or foot.
EDIT: incidentally even in the most car-centric dystopian suburb there are ways to incorporate more walking into your routine. The next time you go to a strip-mall or big box store you could park on the far side of the lot and walk to the door. A minor inconvenience in both time and effort, but you could probably add 1/2 mile or more of walking to your Saturday afternoon errands that way.