Safer cycling? Don't get a helmet and cross red light

[tillson]

Can you point to any credible research that support this? It does not from what I can gather come close to reflecting the Australian Standard on bicycle helmets (or motor cycle helmets) nor does it reflect the findings of research such as:

Cripton, P. A., Dressler, D. M., Stuart, C. A., Dennison, D. R. (2014). Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts. Accident Analysis and Prevention, 70, 1-7.

so very interested in what evidence you have to support your view.

Thanks
Andrew

I can point you in the direction of Newtonian Mechanics and the laws of physics:

For example,

a = ((v1*v1) - (v0*v0)) / 2d

Where:

a = acceleration (a high value of (a) on the brain is what does the damage)

v1 = final velocity (ie 0 when the head has come to rest)

V0 = initial velocity (ie the velocity the head is travelling just prior to it or the helmet striking a solid immovable object such as the ground or piece of street furniture.)

d = the distance over which the head stops. This will be the amount of compression in the helmet foam.

As you can see, if (d) is small (ie very little compression) then (a) is high which is dangerous. With a motorcycle helmet, (d) is many times the value of that of a bicycle helmet because it has much thicker padding and this is why it offers a sensible level of protection.

A bicycle helmet is usually constructed from polystyrene which has very little compressibility. On the inside, you usually find thin strips of sponge which again hardly compress any distance before your skull is hard up against the incompressible shell of the helmet. The sponge is mainly there so that the shell sits nicely on your head, nothing to do with protection.

Sometimes the bicycle helmet will fracture and this may have the effect of slightly increasing (d) in the equation of motion quoted above, but no where near to the levels of (d) found in a motorcycle helmet.

The above is simple Newtonian Mechanics and requires no further reference or proof. The only point open for discussion is the relative values of (d) between wearing a helmet and not wearing one. My position is that (d) is about the same in the two cases. I do accept that a bicycle helmet offers some protection agains abrasions.

 

[halfer]

The above is simple Newtonian Mechanics and requires no further reference or proof.

Your Newtonian mechanics may be sound (I'm not qualified to say) but the scientific method specifically requires claims to be peer-reviewed. If the science is as obvious as you say, there simply must be papers out there that support this view, and contradict the others. This is how non-scientists (i.e. most of us) can be able to decide between two contradicting claims requiring expert knowledge.

 

[KeithH]

No helmet d=0 , a cycle helmet d=1cm or more.
divide something by 0 and you get infinity. the difference between infinity and any other number is.......

 

[flecc]

I'm not a statistician, but I don't think we can extrapolate from that data that helmets make no difference. Even if all cyclists killed on the road in the UK are wearing one, it does not take into account the cyclists who were involved in an accident but survived, nor the types of injuries that were sustained in fatal cases.

Like Aushiker, I think peer-reviewed scientific research is the way forward in this discussion - since anecdotes and personal experience aren't statistically significant.

True Halfer, I would never say they make no difference, nor did I, drawing attention to what they could do. But the stats serve to balance the opposite extreme views on helmet efficacy. In particular they show that they are nothing like effective enough for the introduction of enforced wearing.

 

[Aushiker]

For those interested in being informed, there is a monograph published in 2010 which whilst tending to focus on mandatory helmet laws, also looks at the research to 2010 on the effectiveness of helmets and in particular hospital data. If nothing else it is a good starting point to the literature in the area.

Haworth, N., Schraman, A., King, M. & Steinhardt, D. (2010). Bicycle helmets research.CARRS-Q Monograph Series – Monograph 5. Kelvin Grove, Qld: Queensland University of Technology Centre for Accident Research & Road Safety – Queensland.

Andrew

 

[TREF]

It looks to me that there is a great opportunity for a manufacturer to make a better quality (more effective) helmet for cyclists.

 

[Aushiker]

Your Newtonian mechanics may be sound (I'm not qualified to say) but the scientific method specifically requires claims to be peer-reviewed. If the science is as obvious as you say, there simply must be papers out there that support this view, and contradict the others.

and to follow on from this point it becomes hard to understand why the paper I linked to before concluded in part if the effectiveness of helmets clearly not effective...

In the 2 m (6.3 m/s) drops, the middle of our drop height range, the helmet reduced peak accelerations from 824 g (unhelmeted) to 181 g (helmeted) and HIC was reduced from 9667 (unhelmeted) to 1250 (helmeted). At realistic impact speeds of 5.4 m/s (1.5 m drop) and 6.3 m/s (2.0 m drop), bicycle helmets changed the probability of severe brain injury from extremely likely (99.9% risk at both 5.4 and 6.3 m/s) to unlikely (9.3% and 30.6% risk at 1.5 m and 2.0 m drops respectively). These biomechanical results for acceleration and HIC, and the corresponding results for reduced risk of severe brain injury show that contemporary bicycle helmets are highly effective at reducing head injury metrics and the risk for severe brain injury in head impacts characteristic of bicycle crashes. (my emphasis)

The journal which the paper is published in is what is known as a A* journal, i.e., highest ranked group of journals in the world in its subject area. You would think therefore that the editorial board and the peer reviewers would have a clue.

The paper for anyone interested is:

Cripton, P. A., Dressler, D. M., Stuart, C. A., Dennison, D. R. (2014). Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts. Accident Analysis and Prevention, 70, 1-7.

Then comes into question all the science behind the standards for helmet design for both motor cyclists and cyclists ... seems a lot of people must have got that wrong which simply does not seem logical.

Andrew

 

[tillson]

No helmet d=0 , a cycle helmet d=1cm or more.
divide something by 0 and you get infinity. the difference between infinity and any other number is.......

Let me put some numbers to this:

a = ((v1*v1) - (v0*v0)) / 2d

Say you are travelling at 20 MPH v0 = 9 m/s

d = 2 mm of foam (say for a cycle helmet) a = 20250 or 2025G (most likely fatal even though the G force is for a very short duration)

d = 50 mm of foam (motorcycle helmet) a = 810 or 81G (most likely survivable)

I hope this illustrates that it is mainly about the value of (d) and a bicycle helmet gives you very little.

As TREF says above, these bike helmet need a re-think. I believe that the way forward is a lightweight aluminium honeycomb outer shell which distorts on impact (giving a greater value of (d). The current polystyrene ones are a con (very little (d)).

 

[JohnCade]

Bit expensive though....

http://www.theguardian.com/environment/bike-blog/2012/may/22/airbag-bike-helmet-way-forward

 

[SRS]

Surely the question must be, if you were going to fall head first onto a kerb stone, would you prefer to do it with or without a cycle helmet fitted.

Personally, I'd try it with a helmet fitted.

 

[tillson]

Surely the question must be, if you were going to fall head first onto a kerb stone, would you prefer to do it with or without a cycle helmet fitted.

Personally, I'd try it with a helmet fitted.

Under the circumstance that you outline, a helmet would provide some protection to your scalp, but as far as protecting against a brain injury is concerned, you may not be any worse off without a helmet (see my explanation above for the reason why). Then there is the fact that the helmet only protects part of the head. Contact with the kerb could be with the face, lower side of the head or upper part of the neck. Helmet or no helmet, the result will be the same.

You must also consider a glancing blow which causes the head to rotate. Rapid angular acceleration of the head is a common cause of severe brain and neck injury. The edges of many cycling helmets extent well beyond the forehead, and around the circumference of the head too. This has the effect of providing an extended mechanical level when the helmet receives a glancing blow and will exacerbate the effects of the impact. So it is likely to be detrimental to wear a helmet in these circumstances.

As you can see, it isn't really as simple as saying, "I'd rather be wearing a helmet if I smacked my head on a kerb stone." There is much more to consider.

 

[stevieb]

you first mentioned that you wore a helmet to keep your head warm,
if thats the only reason then why not just wear a hat as there are a lot of varieties to choose from?
but you DO wear a helmet so i suspect that you believe they provide some degree of protection.
thank you for explaining the physics involved when an impact occurs it is very interesting and i will bear this in mind when i buy my next helmet .
i can understand the points that you are trying to make.
But in the meantime i,ll continue to wear mine until something better comes along as my previous two helmets DID save me from impact injuries.
thanks

 

[daveboy]

On a number of occasions I have banged my head on the up and over garage door. I've done this with and without a helmet and it hurts more without. What more proof do you want.

 

[drsolly]

[quote="tillson, post: 221326, member: 991"
A bicycle helmet is usually constructed from polystyrene which has very little compressibility.[/quote]

I certainly agree that Newton's laws apply, but I think your assumption that polystyrene has very little compressibility, is not correct. And that, of course, invalidates your whole analysis. The protection isn't from the 2mm of padding, it's from the 15mm of polystyrene.

It's fairly easy to find offcuts of expanded polystyrene; they are often littering our roads (or try a polystyrene cup). Try the following experiment: press your thumb into the offcut, and notice how your thumb sinks into the offcut. That's the material demonstrating compressibility.

Bike helmets are made of expanded polystyrene that is somewhat less compressible than the pieces you might find lying around; nevertheless, still compressible. If you no longer need your bike helmet, you can experiment with it to verify that for yourself.

The reason it is less compressible than the pieces you might find lying around, is that it's designed for a different purpose - to give protection to a head in the case of severe impact, yet to maintain integrity when mildly bumped on (for example) a branch.

However, if someone else prefers not to wear a helmet, I'm fine with that. It's not my head that could be broken.

 

[tillson]

you first mentioned that you wore a helmet to keep your head warm,
if thats the only reason then why not just wear a hat as there are a lot of varieties to choose from?
but you DO wear a helmet so i suspect that you believe they provide some degree of protection.
thank you for explaining the physics involved when an impact occurs it is very interesting and i will bear this in mind when i buy my next helmet .
i can understand the points that you are trying to make.
But in the meantime i,ll continue to wear mine until something better comes along as my previous two helmets DID save me from impact injuries.
thanks

I have already stated that a cycling helmet will provide protection against superficial injuries to the scalp, and I think that we all agree on that. So yes, I am saying that they do provide some degree of protection.

But, I don't believe that a cycle helmet will protect against heavy impacts which a severe enough to cause a brain injury and I have tried to illustrate why by using basic mechanics in my previous posts. Further to this, I think that a cycle helmet can actually make injuries worse in certain circumstances, particularly to the neck. I have also tried to explain why this so.

I suppose that I wear a cycle helmet now because I started out under the misapprehension that I was protecting myself against serious head injury by using one. Now I realise that they don't provide the level of protection that I originally thought. Balancing all of the pros and cons and the fact that I have already paid for one, I continue to use it.

With hindsight, I think money set aside to buy a cycle helmet would be better spent on a decent rear view mirror. More safety to the pound.

 

[flecc]

On a number of occasions I have banged my head on the up and over garage door. I've done this with and without a helmet and it hurts more without. What more proof do you want.

The crucial words here are "on a number of occasions".

I believe in primary safety, not having the accident in the first place, much more than the secondary safety of protecting against accidents.

Why did you do it repeatedly Dave, not learning from the first time that it's undesirable?

I've never worn a cycle helmet in 68 years of cycling and didn't wear one during the first 23 years of motorcycling since it wasn't compulsory. And I haven't got a mark on me from a road accident, my emphasis on primary safety seeing to that.

But I have had two serious non-road accidents, one at work, one at home, which illustrates how the full-time conscious intention not to have a road accident is very effective. At home and at work I didn't have that conscious intention in mind all the time, hence having those two those accidents.

And of course having permanent no-claim bonus on my vehicles is a very real added benefit.

 

[KeithH]

On a slightly different tack.
How many non helmet wearers would let their children ride out without a helmet?
Despite knowing I should I didn't wear one until my kids refused to cycle with me without me wearing one.

 

[tillson]

[quote="tillson, post: 221326, member: 991"
A bicycle helmet is usually constructed from polystyrene which has very little compressibility.

I certainly agree that Newton's laws apply, but I think your assumption that polystyrene has very little compressibility, is not correct. And that, of course, invalidates your whole analysis. The protection isn't from the 2mm of padding, it's from the 15mm of polystyrene.

It's fairly easy to find offcuts of expanded polystyrene; they are often littering our roads (or try a polystyrene cup). Try the following experiment: press your thumb into the offcut, and notice how your thumb sinks into the offcut. That's the material demonstrating compressibility.

Bike helmets are made of expanded polystyrene that is somewhat less compressible than the pieces you might find lying around; nevertheless, still compressible. If you no longer need your bike helmet, you can experiment with it to verify that for yourself.

The reason it is less compressible than the pieces you might find lying around, is that it's designed for a different purpose - to give protection to a head in the case of severe impact, yet to maintain integrity when mildly bumped on (for example) a branch.

However, if someone else prefers not to wear a helmet, I'm fine with that. It's not my head that could be broken.

The polystyrene used to manufacture cycle helmets has nothing like sufficient compressibility to protect against serious injury. You might get 5mm if you are lucky and that would still subject your brain to a 580 G acceleration, which is likely to be fatal.

 

[tillson]

On a slightly different tack.
How many non helmet wearers would let their children ride out without a helmet?
Despite knowing I should I didn't wear one until my kids refused to cycle with me without me wearing one.

Children are often used by companies to blackmail parents into buying things that they don't need. Suggesting that you are a bad parent unless you buy XXX is a very powerful marketing and sales tool.

 

[Deleted member 4366]

Whenever we get these arguments, people always pick statistics that support their cause. You can prove nearly anything with the right statistics.

Any protection will give you more protection than nothing.

If a truck runs over your foot when you're wearing a helmet, you can be pretty sure that the helmet won't help you much; however, if you were wearing Totectors, it might not hurt so much. Plus, if you joined their Golden Shoe Club, and subsequently died from your squished foot, you would be able to claim the £10,000 insurance money.

Helmets have the additional benefit that they keep your head warm and can make you look more attractive, especially if you're folically challenged, but be careful: Many moons ago Motorcycle News did a survey that showed that motorcyclists were much more likely to go bald than the rest of the population, which they speculated was something to do with wearing helmets.

As it's too late for me to worry about that, I'm happy to wear my helmet most of the time. I don't want compulsion, but I would advise anybody to wear one. You can often get hardly used ones at car boot sales for £1 or not much more if you can't afford to pay £50 in a bike shop.

As I've said before, snowboarding ones are better than cycle ones. They don't look so daft, they offer more protection, and they don't let in wasps that make you crash.