Good question. What risk do I create for others when I choose to drive a car 10 miles? I guess it's a 1/x probability of injuring someone, a 1/y chance of killing someone, and some other probability of injuring or killing more than one person. x and y are large numbers, but as the miles add up, those numbers go down to something significant. It supposes, however, that there are alternate, safer ways to travel.