Helmets
You can follow the various threads here, here and here of the old "helmet discussion" Nemesis. I usually wear mine; the only time I don't is when I wheel up to the local plant nursery a mile away. That said, when the RCCS took our Paris-Redux ride back in April, one of our riders hit a puddle-filled hole going slightly downhill at speed. He catapulted over the bars and landed directly, and I mean DI-rectly on his helmet-ensconced head. Without it he would've been hurtin' for certain. If I have one of those days when I feel like going "free", I'll think back to that day and probably make the safer decision.
Comments
Of course, nothing beats NOT NEEDING the helmet, through knowledge of the five layers of safety and how to apply them, but when it's time for that fifth layer, one doesn't have time to fetch the helmet and get it on one's head.
Generally around 30% of the bikers use helmets here.