A scientific paper on this topic: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1368064 http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1368064 Its con

A scientific paper on this topic: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1368064 http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1368064 Its conclusion: "In jurisdictions where cycling is safe, a helmet law is likely to have a large unintended negative health impact. In jurisdiction where cycling is relatively unsafe, helmets will do little to make it safer and a helmet law, under relatively extreme assumptions may make a small positive contribution to net societal health." The negative health impact is "increased morbidity due to foregone exercise from reduced cycling" as a consequence of mandatory bicycle helmet laws.