With complete respect for zonatnadem, 12 inches is close if you hit a stone or crack in the road and you swerve or wobble a couple of inches. I bet a car wouldn't pass another car(if the driver had any sense) at anything more than a crawl when only 12 inches away from the other vehicle. I also hope they wouldn't pass a pedestrian that close--in the case where a pedestrian has no choice but to walk on the road.