Just want to add - I met a guy a couple of years ago that ALWAYS drove his car with a helmet on. I met him on a snowshoe trip I went on with an outdoor club. This guy said that the majority of deaths in car accidents were related to head injuries, so he always wore a helmet while driving his minivan. I thought he was kidding at first. I was carpooling with him, and he drove from Seattle to the trailhead and back with that helmet on, and all points between. He was completely serious.