Take time to read the article at Bicycling Magazine http://www.bicycling.com/senseless/ It was worth the time and the length. Nothing is more important.
Bicycle helmets do an outstanding job of keeping our skulls intact in a major crash. But they do almost nothing to prevent concussions and other significant brain injuries—and the very government agency created to protect us is part of the problem. The time has come to demand something safer.