I just spent the better part of a half an hour I will never get back speed reading this thread so I admit I could have missed the thread that mentioned the revenue potential of a law requiring helmet use for adult cyclists. In my city an adult can be (but rarely is, unless ...) stopped if their bicycle does not have: bell, reflectors, 200' lights. Fines start at $200. If you were stopped because a taillight was out on your car the fine would be $65. A cyclist without a helmet sticks out like a sore thumb. There aren't many of them, but were it illegal I can well imagine the fine for not wearing one would be >$300 for a first occurrence, ~$1000 for a second, and that is far more likely the genesis of any proposed legislation vs overwhelming concern for a very small percent of a very small percent of road users. When in doubt, always follow the money.