[snakeboy]

I would assume there is quite a lot of evidence for the efficacy of helmets in the event of a crash, no? I think in general it makes more sense to give credence to studies that give intuitive results that are explainable by sound first principles modeling, rather than one study that gives an unintuitive result based on human behavior.

[ThatGeoGuy]

Not really? There may be slight reductions in some injuries as a result of helmet use, but for most cyclists this isn't really what you'd call definitive data. At the end of the day, a few inches of foam isn't going to protect you from a few tonnes of steel.

That said, it's notoriously under-studied. If you look into "best helmet" in terms of safety you'll see a lot of marketing speak and not a lot of science. The way that helmets are tested tend to 1) not be reflective of actual use of the helmet in a conflict scenario and 2) tend to make pretty broad assumptions about the largest danger factor on the roads.

The thing is that you would /think/ that there's a lot of evidence out there for helmet use. The most compelling evidence for helmet use is for drivers in cars / automobiles, and we wouldn't dare mandate that into existence.

Helmet laws always seem to get people ruffled up but at the end of the day the number of bike fatalities is already low, and skewing that in terms of helmet use somewhat misses the point - dedicated and separated bicycle infrastructure will have a vastly larger impact compared to any mandate on using a helmet. It seems like arguing about adding a mandate on helmets is just an easy way for the system to wash its hands of responsibility for not regulating vehicle and street design more thoroughly.

[peoplefromibiza]

> Not really? There may be slight reductions in some injuries as a result of helmet use,

Yes, actually, really!

Helmets provide a 63 to 88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7025438/

There was a significantly higher crude 30-day mortality in un-helmeted cyclists 5.6% (4.8%–6.6%) versus helmeted cyclists 1.8% (1.4%–2.2%) (p<0.001). Cycle helmet use was also associated with a reduction in severe traumatic brain injury (TBI) 19.1% (780, 18.0%–20.4%) versus 47.6% (1211, 45.6%–49.5%) (p<0.001), intensive care unit requirement 19.6% (797, 18.4%–20.8%) versus 27.1% (691, 25.4%–28.9%) (p<0.001) and neurosurgical intervention 2.5% (103, 2.1%–3.1%) versus 8.5% (217, 7.5%–9.7%) (p<0.001).

https://bmjopen.bmj.com/content/9/9/e027845

“The evidence is clear: helmets save lives and significantly reduce the risks of severe injury,” said Lois K. Lee, MD, MPH, FAAP, lead author of the statement, written by the AAP Council on Injury, Violence, and Poison Prevention. “And yet sports-related injuries make up a substantial proportion of all traumatic brain injuries. As a pediatric emergency medicine physician, I advise all my patients – and their parents-- to wear helmets.”

https://www.aap.org/en/news-room/news-releases/aap/2022/amer...

[ThatGeoGuy]

I don't think I'm necessarily disagreeing that in the worst-case scenario that helmets do the job of reducing brain and skull trauma. Doing something is the alternative to doing nothing, you'd expect some difference here.

My problem is that helmet use isn't exactly "well-studied." All these studies look at existing reports from medical centres on injuries & deaths. This doesn't actually account for the broader behavioural changes in the system, or look at causes outside of "injured while wearing a helmet vs. not."

In any other industry this kind of reporting (while factual) is absolutely ignoring everything else. A short list of what isn't being considered:

- Which road and behaviour led to incident?

- Which kinds of road conflicts can be addressed by helmets?

- How did road design lead to the incident?

- Were environmental factors a concern (winter, ice, rain, etc.)?

- How does behaviour for the cyclist change as a result of not wearing a helmet?

- How does behaviour for other road users change as a result of a cyclist not wearing a helmet?

- What kinds of helmets are more viable for protection in the case of the most extreme (and most common) conflict scenarios? How do we then test these helmets to ensure compliance in manufacturing?

These are all questions you'd expect to be answered here, and then you'd do the cost-benefit analysis on whether a mandate is necessary or not. A "well-studied" field would have discussed these effects in broader detail, not just short-cut to "fewer people who already had huge injuries while cycling died when using a helmet." That is not the entire problem, because it leaves out a huge sampling of people who do not wear helmets and do not make it to the hospital in the first place.

[seadan83]

The kicker is rate of head injuries during a bicycle crash. A fraction of crashes involve a person's head (though when it does, for those one in ten falls, you really want it)

The numbers are under reported. Every cyclist I know that uses a bike for transport has been hit by a car. Myself thrice, never reported. Crashes involving myself, never reported. Hence, there is a bias in the data for the really traumatic injuries

[ndsipa_pomu]

There's some debunking of helmet studies here: https://www.cyclehelmets.org/1027.html

[peoplefromibiza]

thanks.

A very good example of what "selection bias" means.

[banannaise]

Bicycle helmets are designed to protect riders from collisions with terrain at normal cycling speeds (in fact, less than that; helmet tests are done with a speed of about 14 miles per hour [0]).

Cyclists who are hit by traffic are likely to be hit much, much harder than that. Therefore the effect of the helmet is more or less entirely untested, and manufacturers have no incentive to design helmets for that scenario.

[0] https://helmets.org/limits.htm

[lukas099]

I intentionally said IF it's the best research we should listen to it. I'm agnostic on whether or not it is the best research.

[cryptonector]

I got to witness an accident where a helmet would have made a huge difference for the cyclist. A lady was cycling at fairly low speed on a street that had old rails, then her front wheel apparently got stuck in a rail and she fell over and got a pretty serious looking head injury. Several of us in cars pulled over, called 911, and waited till the ambulance arrived and told them what happened. I have no idea what happened to her in the end, but she was unconscious and bleeding profusely from her her. She was not wearing a helmet, as you might surmise.