If nothing else, my helmet is for another layer of visibility. One of those bright chartreuse Garneau things that Performance sells. I find on my commute that when cars are coming out of driveways or their vision of me is somehow blocked, I can stand on the pedals and let them see the helmet coming. It seems to work (along with eye contact).

That Dutch video is great. I wonder, though, if Dutch bicycles are considered vehicles, as here.