Are those helmet laws for adults or children? I'm guessing that all laws in the USA apply to children only, or to only off-street use like mountain bike trails. That is why I specifically asked about adults in the original post. I have never heard of a USA city or state requiring helmets for adult cyclists on public streets. If these laws exist, I would be interested in hearing about the specific locations.

I am not especially pro or con helmet laws, but I would like to know what exists right now.