This is such a highly emotive topic that I've been ruminating for a while. Given I'm a new poster here I hope it's ok to add my €/£/$ 0.02.

I'm in my early 40s and grew up in Germany. Everyone rode bicycles for transportation and many for recreation, if they were mobile at all. In my family, only my 80+ y.o. grandmother who had really bad legs didn't. Our school had a huge bike parking lot. We went out with school classes or rode to the next town over even. And no one of course wore helmets. Now I know that doesn't meant they are a bad idea at all, but it's context that's important for some. Because while it was just understood that you wore a helmet on a motorbike, moped or scooter, and a seat belt in a car -- all of which were legal requirements -- it was also understood that if your bones were of normal resistance to fracture, you didn't need a helmet on a bike.

Then when I was a young adult, little children (3, 6, ...) were being equipped with helmets while riding. It seemed a bit like part and parcel of the increase in attention to protecting children from accidental harm that has happened since the days I was allowed to run wild on my bike. And overall, in my respectful humble opinion, overprotection isn't a good thing. But it STILL doesn't mean helmets aren't a good thing.

Then the parents of the behelmeted children started wearing helmets, coming across as somewhat sanctimonious. And some of my peers did -- those that fancied themselves more macho riders. Mountain bikes had become commonplace, even inside flat towns. But also interesting new faster bikes than our old 3-speed hub geared or MAYBE tamely rear-derailleured rides of my youth.

I had a time I didn't ride much then - I was living in Paris, but when I was riding it was still without helmet.

But when I started to ride more and more over the last years, by then in London, something had shifted. Relations between cyclists and drivers were a lot more contentious than in my youth. Drivers in London and Paris, unlike Germany or the Netherlands, aren't as educated in the needs of cyclists -- because they aren't necessarily cyclists themselves. I had a lot of rather tense situations, and it started occurring to me that a helmet would maybe not be completely useless.

And then, a year or so ago, my girlfriend (who's American -- we were in a LDR then) was aghast I was riding without a helmet. Even though she's older than me, HER American socialization as a college-educated mostly sporty recreational rider (with a fast WSD Trek road bike and a good ATB for the dirt trails) had taught her that when you ride, you wear a helmet on a bike, just like you wear a seat belt or a motorbike helmet.

So I got one and have been mostly riding helmeted since then. Not always. It still feels completely ridiculous to put on a helmet to roll a km or two to the café during lunch break.

But I live in the US now, too. In Fairbanks where there are a lot of cycle accidents. And even though I have doubts about its efficiency -- after all, the road safety videos from my youth about wearing moped and scooter helmets had stressed that nothing short of a full "integral" helmet with a stiff part around the chin would protect your head -- it's probably better than nothing. Still, we saw the videos of the melon in a moped-style half helmet, which is a LOT more covering and solid than a bike helmet, and it got smashed to pulp nonetheless.

But yes. Riding faster and faster in more and more cyclist-unfriendly places it makes more and more sense.

If I were to go back to Germany or cycle around in Amsterdam, I don't know if I could bring myself to putting on a helmet, though. My old danger assessment said "not necessary, or not significantly likely to be needed or helpful" and nothing changed in the circumstances in THOSE kinds of places. I'm more feeling akin to my friends who'd think I've gone soft in my head on my old days and ask me if I wrap myself in cotton wool overnight.

So that's what I am -- one of the closet non-bike helmet cyclists who wear a helmet anyway.