Yeah yeah, always wear a helmet, bright safety clothes, ride with traffic, signal your intentions....didn't help my cousin

But yes, helmets save lives. Funny thing seen on the commute last week, I normally would not do this but stopped a guy leaving the train then realized with his limited English had to use jesture, pantomime, turning his helmet 180 degrees, his was on backwards.

I suppose, protects your head just as well that way.