According to Dr Mayer Hillman, Senior Fellow Emeritus at the Policy Studies Institute in London, who has undertaken the only major international research of the evidence on the use of helmets, you're better off not wearing a helmet.
"By wearing helmets, cyclists are, at best, only marginally reducing their chances of being fatally or seriously injured in the rare incident of a collision with a motor vehicle."
Dr Hillman believes that by being more careless, the helmet-wearer is using up any extra protection offered.
"Cycle helmets provide limited protection for the head. Neither manufacturers nor retailers tell the public this."
"You're much better off cycling with extra care than you are wearing a helmet and riding with an exaggerated sense of security," says Hillman.
"Non-cyclists say they don't cycle because they think it's too dangerous. If you tell them they should always wear a helmet when they ride you're reinforcing their belief that it's dangerous. I have calculated that the health benefits of regular cycling in terms of life years gained through increased longevity, far outweigh the loss of life years in cyclists' deaths."