I didn't realise that bicycle helmet wearing wasn't compulsory in the US. It is here, and has been for quite some years. It's a bit like seatbelt wearing in vehicles - it becomes second nature - although some people are still resistant to change/authority/whatever. It amazes me how often drivers are killed or injured by being thrown from vehicles, because they failed to wear a seatbelt. For us, it's a reflex action - get in the car, grab the belt - even if we're only traversing the farm.