In my area of rural USA, a four person family (two driving age kids plus parents) has four cars, because there is no public transport, and the distances are too long to walk or bike. In this case, that might be pared down by one or two cars. My husband's car, driving him three towns away to get the train into the major city, then sits in the lot all day too far away for me to use. I would happily give up a second car and use one car for the both of us, since I have a much shorter commute, and closer errands to run, and can get the car to go back to the train station and pick him up. I can't see sharing with neighbors or strangers, but it would be convenient for us. If I had driving age kids living at home, they could either share parent car or split one between them. Given teenage driver accidents, that would be less worry for parents as well. So, might remove some cars from multi car families.