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Comment by carlob | Hacker News Reader

Two important things about helmets:

1. Helmets are very very useful if you're riding fast. In fact they are mandatory in all cycling sports. However most people don't commute to work going much faster than they would if running, hence they are not very useful for them.

2. In countries where helmets are compulsory, the chilling effect of risking a fine for not wearing a helmet has meant a decrease in the number of cyclists. Now, since bike accidents are relatively rare, but the health effects of cycling to work rather than driving benefit every single cyclist, helmet laws tend to have a negative effect on public health.

This said, whenever I'm going for a sporty ride (longer, or faster than usual) I usually wear a helmet. When riding 5 minutes to meet a friend for a beer I don't.

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helmets are really useful if you are riding slow too, I was pulling out of a driveway, there was a little bit of black ice that I didn't see, my front wheel went out from me and before I knew it I was down: could not react, one second I was upright, the next second I was on my side and yes, my helmet was cracked by this fall (hit the side of my head on the cement), if I didn't have it it'd have been a much worse day than the very mild headache I got from it.

I really don't understand all these "helmets don't help" folks, having ridden motorcycles and bikes all my life you would not catch me dead without a helmet: a helmet is not an invulnerability cloak but in the end if you fall down and hit your head and you don't have one, you are not going to be in a good place, whether you are going at walking speed or 30mph.

The reason some are sceptical, is the extra weight and leverage of the helmet is supposed to increase the chance of you breaking your neck in in accident.

I have no idea if its true or not.

Then why don't you wear a helmet when you're walking on ice as well?

I'm not saying helmets don't work, I'm saying it's not very likely to hit your head at high velocity on the ground if you were going 10 km/h. And if that means you're not gonna ride a bike at all because you forgot your helmet you're probably having a higher risk of cardiovascular disease further down the line than you have of breaking your head now.

Well, I do wear a helmet while skiing - largely because I witnessed an accident where a stationary skier was hit on the head by a flailing T-bar.

Having known someone who died to a head injury from falling down from a standing position; speed matters little, other than giving you more time to react. Just the acceleration from gravity is enough to fuck your head up pretty badly.

Head injuries are nothing to take lightly.

> Then why don't you wear a helmet when you're walking on ice as well?

Because bikes constrain falls. Millions of years of evolution plus my own personal practice means I'm pretty good at falling safely. But when I am wrapped around a bike, a lot of that goes out of the window.

Also, I'd like to see some stats on your "not very likely". In 20 years of adult riding, I've fallen twice at low speeds hard enough to crack a helmet. And that's not counting the time as a kid I knocked myself unconscious on a low-speed ride.

> because you forgot your helmet

Is this a problem people have? When I'm not riding, I clip my helmet to my bike. This doesn't strike me as a particularly challenging habit to develop. Maybe just keep necessary equipment together? That sounds easier than trying to decide whether the odds are small enough to risk traumatic brain injury.

> Also, I'd like to see some stats on your "not very likely". In 20 years of adult riding, I've fallen twice at low speeds hard enough to crack a helmet. And that's not counting the time as a kid I knocked myself unconscious on a low-speed ride.

And in 28 years of both adult and kid riding, with some years totaling over 3000 km, I've fallen several times, even cracked a couple of ribs, but never once hit my head. See that's the problem with anecdotal evidence.

> I clip my helmet to my bike

Do that in Rome, you'll come back to find none.

> See that's the problem with anecdotal evidence.

I'm not the one who said "not very likely". I'm not offering my story as evidence, just as an explanation for why I'd like evidence.

> Do that in Rome, you'll come back to find none.

I was speaking of the "I am going riding now" case. In Rome can you leave your bike outside overnight? In SF you can't, so people store bikes and helmets indoors. In which case, I'd submit that storing them together is a pretty good idea.

Helmet theft might be a problem here in the "I am already out riding" case. Where I worry about that here, I clip my bike to my bag, so again it's not a "I forgot my helmet" problem.

> I'm not saying helmets don't work, I'm saying it's not very likely to hit your head at high velocity on the ground if you were going 10 km/h.

Because if you fall over while walking, you're likely to manage to get your hands down before you head hits the ground. You have nothing to lose by getting your hands down quick.

By contrast, when you run into problems while cycling, your instinct is to try and regain control of the bike. You don't immediately drop the handlebars, You keep your hands on the bars and try to steer/brake. Moreover you're likely to go over sideways and only one hand tends to be able to break the fall.

A fall from a bike and a fall from your feet is a massively different thing.

> my helmet was cracked by this fall (hit the side of my head on the cement)

I'm not sure whether helmets really work, and just to be on the safe side I almost always wear one, but I seem to remember one European biking site -- possibly mentioned here in HN... I forget -- where the author argued that helmets are designed to crack so that it seems they work. But, he argued, whether they crack or not bears no relation to protecting from head injuries; the crack simply leaves you satisfied that the helmet "saved" your life.

The article seemed convincing. Sadly I cannot remember where I read it.

They are definitively designed to crack as that's a core way for it to absorb the energy of the hit. Similar to how a car crumbles in an accident. Otherwise it's just transferring the kinetic energy straight to your head.

This is also why you should replace helmets after a fall and every few years since the material they are made of degrades with age.

I don't remember if the following link was the site, but in any case it makes similar points (disclaimer: as far as I can tell, this seems to be a "helmet skepticism" advocacy site, so take it with a grain of salt):

http://www.cyclehelmets.org/1209.html

> "It's not a simple matter to draw conclusions about the benefit a broken or deformed helmet might have provided in a crash. However, the fact that serious injury to unhelmeted cyclists is as rare as helmet damage is common, suggests that most of the claims of benefit from damaged helmets are likely to be exaggerated."

> "The next time you see a broken helmet, suspend belief and do the most basic check – disregard the breakages and look to see if what's left of the styrofoam has compressed. If it hasn't, you can be reasonably sure that it hasn't saved anyone's life."

The point seems to be that anecdotes of the type "my helmet worked and saved my life, see? It's cracked" are not conclusive.

If a helmet cracks, it's absorbed energy, cracking is simply how it's designed to dissipate that energy. Whether it cracks or not, it should be replaced when it absorbs energy from a fall.

No. The helmet, in the ideal conditions for which it is designed, should /crush/. Cracking is a non-ideal failure mode as it absorbs much less energy.

hmmm ... interesting point

Looking into the documentation around bicycle helmet design, it appears that the outer surface is actually less for energy absorption, and more for preventing any "catching" on the road surface which would add torque to your head in a crash.

Cracking, in this case, is the expected failure model, since the material has to be hard to provide a sliding surface.

Helmets should not be re-used after a crash.

http://www.bhsi.org/ideal.htm point 5 - outer shell

Well, when we talk about a helmet cracking as opposed to specifying "the outer shell of the helmet" I think we're talking about the whole polystyrene core.

Definitely. The two accidents I've had where helmets have been helpful have been at low speeds. In one, somebody stopped suddenly in front of me while I was novice rider getting used to new brakes. The other, I hit a wet tram rail while making a turn. The problem wasn't total velocity, it was me falling over while being conjoined with a bike. (I also had one accident at speed, but there the bike and I parted ways and I supermanned through the air and kept my head up on landing.)

The study persuades me not at all for a few reasons. 1) it's Canada, 2) it's all of Canada, and 3) it's only in-patient hospital stays.

I'm biking in a US urban area. I know that Canada's automotive death rates are lower, and I'm happy to believe that's due both to Canada's famed niceness and to a more European attitude toward infrastructure. I might also not bother with a helmet tootling along some leafy Canadian rural road, but when dealing with California's drivers in an environment that's mostly cement and metal, thanks, I'll take the helmet.

I also get the theory that in-patient hospital stays might be a good index to help decide the public benefit of helmet laws. But I don't think my helmet kept me from two hospital stays. I think it kept me from two concussions. Given the long-term cognitive effects of even nominally mild brain injury, I'm again sticking with the helmet. Those here who think themselves so smart that a) this study proves it for them, or b) they have smarts to burn are welcome to go without.

I'm sorry, but you really have no basis for saying that "if I didn't have it it'd have been a much worse day than the very mild headache I got from it."

I think we can have it both ways. For a given rider, on a given trip, any fall will be safer if they are wearing a helmet. However, statistically, it is argued, many falls won't be much safer. And in fact, if they feel compelled to wear a helmet, the person won't ride at all. And many of the rides the don't take would be ones where the likeliest falls are likely to not be helped much by a helmet.

I subscribe to the above reasoning. A population may be healthier if not compelled to wear helmets when cycling. But for me, I never ride without one. Ever. Short trips, long trips, commutes to work. I have mine with me now.

As a corollary to your point #2, there is a clear safety in numbers effect in which as the number of cyclists goes up, the rate - and often the absolute number - of crashes and injuries goes down.

Yes I was going to edit to add that, but you beat me to the punch.

http://www.ncbi.nlm.nih.gov/pubmed/18481926

In Finland, wearing a helmet while bicycling is required by law, but there aren't any penalties set for not complying. Maybe this appeals to people whose moral includes unconditional law-abiding.

I don't buy the idea that requiring helmets truly reduces the number of riders long term. The kind of person who would not ride their bike because they don't want to wear a helmet is the kind of person who was only going to die for a couple of months anyway. Every dedicated rider I know wears a helmet, required or not.

Take a trip to any large city with a bike sharing program (say Paris or NYC) and you'll thousands of people renting a bike for a short ride, maybe just because they've missed the bus. As far as I know bicycle fatalities in Paris have gone down since the program was introduced even if the number of bikes on the road has increased by an order of magnitude.

Also you might not buy it, but the data is out there…

30% fewer cyclists in NZ and Australia

http://www.fubicy.org/spip.php?article191

Aye, there's the rub. I would not call myself a bicyclist, and certainly not a dedicated one.

I just ride bikes when it's convenient: there's a pretty good public transport network around my city, you can walk short distances, and car traffic is also reasonable; biking supplements these three options very nicely, esp. now that there's a bike-sharing thing in the city (unlock a bike via an app, ride it wherever, lock it via the app again, minimal fuss). Lugging a helmet around, just in case I should decide to use a bike, is rather inconvenient (I tried). If there were a mandatory helmet law, it would certainly increase the gap between "casual rider" and "dedicated bicyclist," driving out people like me.

(OTOH, if I'm on a bike trip, I do have my helmet, as I usually go beyond paved streets, longer distances and probably higher speeds. Different tools for different purposes.)

TL;DR: assuming "bicycling requires dedication" reduces ridership by definition.

What kind of riders are you thinking of?

In Copenhagen, where everyone rides bikes (young, old, hipster, business guy, dad, child - not only "dedicated riders"), there are plenty who would bike less by simply dropping some bike rides if they choice was between bike+helmet and eg. walking, bussing or cardriving.

Urban commuters and casual bikers in Holland who wear helmets: approximately 0. I don't know what would happen if they made helmets mandatory, but subjectively, needing to put on safety equipment to go to the supermarket three blocks away, or to the pub, is a significant difference in convenience and ease. Mostly because you need to keep the helmet somewhere. In Holland this would likely mean a table for six at the pub has five helmets on or near it. Might be a small problem in the grand scale but it would be annoying.

The Dutch are able to dispense with helmets only because they have pervasive, well-maintained bicycle infrastructure and flat terrain. I'm on the fence about helmet laws in the U.S., but given our road conditions I think everyone should choose to wear one.

And because drivers here are on the hook in any accident involving a bike short of someone throwing themselves under your car.

Yes, drivers here can quite literally get away with murder.

Sure. I think conditions vary from city to city, neighborhood to neighborhood even. That's why I don't support helmet laws. They impose inconvenience and reduce personal freedom. Holland happens to be entirely flat and suited for safe biking, so it's a good example for why helmet laws are not universally a good idea.

I think it's worth mentioning that re #1 this is because of the increased probability of falling off while riding at the limits of human reaction in a dense pack. It is also worth noting that there is no demonstrated prophylactic effect from wearing a helmet in those situations for life-threatening head injuries.

> Helmets are very very useful if you're riding fast.

I can't find a reference with a short Googling, but as I recall helmets only help in a fairly narrow window, something like 18-23 mph or so. If one's going sufficiently fast, they're unable to do much good (because the forces are too much for a flimsy assembly of foam and plastic to reduce enough to prevent injury or death).

> In fact they are mandatory in all cycling sports.

They're the equivalent of a elephant-repelling rock.

> I can't find a reference with a short Googling, but as I recall helmets only help in a fairly narrow window, something like 18-23 mph or so

I'd really like a citation on that. I'm into motorcycles and while helmet design is different, every motoGP season has plenty of examples of riders tumbling at +100kph and walking away after.

The problem is, almost any non-biking helmet is way better than the usual biking-helmets. So no conclusion can be gained from those for biking.

I too would like a citation. Plus calling a bike helmet's foam "flimsy" makes me question your argument. If you've ever removed the outer plastic (which is designed to crumble), you'd know that the foam is extremely tough.

You could likely make the argument that over a certain speed your other body parts will sustain large enough injuries for the bike helmet to not matter, but that's not what you're arguing, you're arguing that the bike helmet itself stops working at an extremely low speed of 23 MpH or above.

I actually Googled this a bit. Cannot find anything on it.

Ah, here's one from a pro-helmet resource: http://www.bhsi.org/limits.htm

It indicates that helmets in the U.S. are only tested for 14 mph impacts.

It's not that the helmet stops working altogether, it's that the helmet's protection really isn't sufficient. It'd be better to wear a full-face motorcycle helmet, but of course that'd be miserable on a bike.

Helmets are generally designed to handle the vertical component of the fall, not your forward velocity.

If your torso hits a solid object at 30mph, there's about ~50% chance you'll rupture your aorta[1]. Hit something like a narrow signpost pole at 30mph and you'll be in a whole world of trouble - I'd post a link to a thread on a motorcycle forum, but it's a bit grisly. Guy survived, but he had to be opened up to treat the internal injuries.

Motorcycle helmets have mostly the same minimal impact requirements of preventing brain injury from the vertical component, but also need plenty of abrasion resistance.

[1] I heard this on London Met police BikeSafe day, a day-long course where London police do a presentation to motorcycle riders and go on an ride with a police observer. But for specific reference, see http://www.nhtsa.gov/people/injury/research/pub/HS809012.htm... - "UK Department of Transport Traffic Advisory Leaflet 7/93 (TAU, 1993), figures quoted are, for 20 mph impact speeds: 5 percent death, 65 percent injured, and 30 percent uninjured; for 30 mph impact speeds: 45 percent death, 50 percent injured, and 5 percent uninjured"

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