Crappy medical study of the day. A couple of busybodies sit around at a playground watching kids play, and form unscientific and annoying opinions about telling everyone what they should be doing. This time they see that most of the kids are not wearing helmets, and announce that someone should intervene and make them wear helmets.
Design: We watched our kids play at the park, and while we were there we took notes on how the other kids were playing.
Conclusions: The kids were not sufficiently restrained and were having too much fun. All the parents should be sent to a re-education camp so they'll force their kids to play the way ours do.
California already has a law mandating helmets for kids on bicycles, and is considering a similar law to cover other activities like roller skating and skateboarding.