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Comment by fab13n | Hacker News Reader

Tested at 20km/h; IIRC that's how normal bike helmets are tested too.

My problem is, I'd bet that crashes causing serious harm happen way faster than that: 20km/h is the average speed of a champion marathon runner, and no one runs with an helmet. My 2nd guess as to why is that if helmets were effective when it matters, at higher speeds, they would look very similar to a motorcycle helmet, and be impractical.

So, facing the choice between something that does its job, and something ineffective but slightly less impractical, lawmakers try to make the latter mandatory. It reminds me of the TSA "security" policies...

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Physics people, physics.

How fast you're travelling is mostly irrelevant, what matters is how hard your head hits the deck. The street surface is perpendicular to your velocity, so your head generally receives an impact no harder than if you had just fallen over while stationary. This betrays the real problem - the average impact speed of a motorcycle head injury is only very slightly higher than that of a cyclist, mainly due to the extra mass.

We know that motorcycle helmets work very effectively. They are markedly superior to cycle helmets in two main respects - they have much thicker EPS foam and so can absorb much more energy, and the smooth round shape of a motorcycle helmet reduces torsional forces on the head and neck, which can be just as lethal as impacts.

The problem cycle helmets have is in providing sufficient protection while still being acceptable to consumers. There is nothing stopping manufacturers from producing cycle helmets that vastly exceed mandatory or voluntary standards (Downhill-specific helmets do) but most cyclists are simply unwilling to wear a large, heavy helmet.

Personally, I think the actuarial data leads to an obvious conclusion - we should do whatever maximises the number of cyclists. The risk of being killed or injured while cycling is completely outweighed by the health benefits of physical fitness. In addition, a number of studies indicate that "safety in numbers" is the most important factor in cycle safety - the more riders on the road, the better other road users become at accommodating them.

"How fast you're travelling is mostly irrelevant, what matters is how hard your head hits the deck. The street surface is perpendicular to your velocity, so your head generally receives an impact no harder than if you had just fallen over while stationary."

Out on the street, there are plenty of vertical surfaces you can hit (lamp posts, trees, curb of the road, or just irregularities on the road surface)

That is why motorcyclists wear helmets, while pedestrians do not, although their center of gravity is higher than that of a motorcyclist.

    My 2nd guess as to why is that if helmets were
    effective when it matters, at higher speeds

It matters at low speeds. Falling over the handlebars of a near-stationary bike and on to your head is a serious injury. I've done it with a helmet on and taking some of the blow in my arms, and still had to lie down for an hour afterwards.

You should look up the speed car crash tests are done at. There are also really slow. The car industry---for obvious reasons---isn't very keen on raising the standards to some realistic speed (like 100km/h or 130km/h).

Marathon runners aren't generally dodging the mirrors of automobiles driven by inattentive people.

Do you really believe bicycle helmets are completely ineffective? I'm going to have to call [citation needed] on that, because having at some hard padded thing on my head seems like it should at least help somewhat. Concussions, etc.

It's contentious. It's suggested they may prevent certain injuries (fracture) but exacerbate others (rotational/shearing). So wearing a helmet may prevent a large number of lesser injuries at the cost of causing a smaller number of more permanently damaging ones (although this a problem people are working on) http://en.wikipedia.org/wiki/Bicycle_helmet http://www.abc.net.au/news/stories/2010/08/17/2985631.htm http://members.pcug.org.au/~psvansch/crag/h-i-mech.htm

There's plenty of advocacy sites if you google for them.

A very nutshell summary is that the minor benefits are accompanied by minor drawbacks. For example you'll not get much benefit if dragged under a 16-wheeler and research shows that drivers will come closer when overtaking someone wearing a helmet.

A major problem though is that well-meaning types want to legally enforce helmets in the name of safety. An immediate impact of this would be to reduce cycling amongst those who think helmets are a nuisance or uncool (as well as another reason for cops to hassle the poor/minorities for breaking laws that they won't bother the better off about). It's fairly well documented that more cyclists/cycling means safer cycling so anything that discourages cycling makes the remaining cyclists less safe.

I don't believe it's completely ineffective; it can certainly save your scalp from some road rash, and I'm sure you can find a couple of cases where a helmet avoided genuine head trauma.

But I'm not convince that the benefit of helmets for cyclists far exceeds the benefit of the same helmets on pedestrians, or on car passengers. Now, most people agree that there's a comfort/price/benefit compromise, which makes it inappropriate to enforce mandatory helmets onto pedestrians, although it would obviously save some lives. In order to accept that what applies to pedestrians doesn't apply to cyclists, I'd like to get some hard data, not some "gut feeling" from lawmakers who barely read what they vote for.

Also, I could understand that serious head traumas avoided in significant numbers would justify a law: in most civilized countries, the corresponding hospital bills and disability grants are paid by public insurance, i.e. taxpayers; cyclist are therefore accountable in front of them. But if it mostly saves scalps from roadrashes, I don't think that a law is appropriate.

There was a study that car drivers would benefit far more than cyclists from wearing bike helmets. Apart from there being 100x as many car drivers - there were a lot of accidents were the seatbelt saved them but they suffered injuries hitting the dashboard (this may have been before airbags).

Many years ago a neighbor of ours, riding his son's motorcycle at something around walking pace, collided with his daughter's bicycle, and fell off on his head. He died, she got away with a broken arm.

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