I'll keep my helmet thanks, I'm just going to grow my hair out.
The main issue I have with that research is that a helmet is not about AVOIDING getting hit by a car, it's there for when you DO get hit.
Reminds me of a comedian's line (can't remember who) referring to people staying behind during a hurricane:
"It's not THAT the wind is blowing, it is WHAT the wind is blowing. If you get hit by a Vooooolvo...."