If only they'd worn a helmet...

Seatbelts like many/any other part of a car are tested above and beyond the speeds they are expected to encounter during use. Even the barriers alongside motorways will be tested having cars on tow ropes crash into them at 100mph+ just to gague what happens and how they can improve the products. If you look at automotive safety and how it has advanced you will learn a great deal about how the products evolved based on testing and evidence. Even the steering wheel which must be collapsable in a crash has more research put into it than any bicycle helmet on the market.

If you liken this to bicycle helmets you will soon see that many announcing them as useful in a road traffic crash with a car assumed to be driven at 30mph+ have no evidence or testing to base supporting the product on. Bicycle helmets have a single test of a 12mph impact on the crown(dropping a weight from 3m onto the top of helmet) and that's it. There is no will to improve or evolve the testing as there is no conclusive evidence the helmets do anything reliably when involved in crashes. They anecdotally are saving lives and anecdotally are hampering surgeons or snapping necks by complicating crashes.

I can't see anywhere in life that you would purposefully buy/use a product far beyond it's designed use without the expectation that it would fail.

Now I don't really know anything about helmet testing, but you've pulled the debate into whether or not helmets are effective at protecting head injuries. If you ignore other factors (ie. Whether you are more likely to be hit in the first place), then a series of major studies have shown that helmets could prevent the chance of serious head injury by up to 65%.

Hope you don't mind if I just link the article I found it in rather than the actual study. Seems to do a good job of telling both sides of the argument:

https://www.theguardian.com/lifeandstyle/2017/mar/21/bike-helmet-cyclists-safe-urban-warfare-wheels

Basically even if there is anything I can do to minimise the chance of something I enjoy (cycling) turning me into a vegetable I'll take it.

@skydancer I meant it makes sense for the riding I do, which is more off-road, light touring, towpath to work sort of thing. I'm sure if you spend all day in traffic it might even be safer to perhaps not wear one depending on the cyclist. Although I did once headbutt the back of a van.

Lets put them alongside steak knives so we aren't confused by them both being safety products but instead just products.

The test for steak knives being good is showing them cutting meat so if you want a lesser test(30mph down to 12mph) why not cut butter with it and call it adequate?

Good luck cutting your steak with a butter knife? Bicycle helmets with motor traffic?

So you're saying because helmets are not designed for impacts at any speed greater than 12mph there's no point in wearing one at all?

Don't we all?

If they aren't designed for impacts at any speed greater than 12mph just think of all the other dare I say better improper uses of them you could be using them for, I think the bmx style ones would make rather fetching hanging baskets for plants.

Are ski helmets any better?

Are ski helmets any better?

No, they don't tend to have the drainage holes that you really want a hanging basket to have.