Cycling UK Forum

Bananaman wrote:One of the things about statistical inference is that is just too suceptible to the large number of factors to prove a useful basis for reasoning in many situations. Some (most visibly politicians and spin merchants) often make an art form out of twisting statistical inference.

One of the arguments in the OJ Simpson defense was that several million woman in the UK suffer from domestic violance, but only a few 1000 of these end up begin murdered, therefore the probability of OJ doing it was one in a few thousand.

Others have pointed out, that of the few thousand abused woman murdered most (70-80%) were murdered by their partner. Therefore OJ probably did it.

Some times common sense is a much better guide than stats. Helmets are designed to absorb 12 mph of impact. Thats a significant cushion that anybody involved in an head impact is going to appreciate.

We do not need 'proper statistical analysis' to reason. There are many other, more reliable ways of doing it.

Common sense is just as bad imo. Given that helmets can skew injuries by creating new ones, the common sense argument that something between an hard object and your head is the best bet can (but not necessarily) fall apart.

Whilst extrapolation of 'other' data sets is a bad idea, I'm sure enough cyclists are being killed/injured each year both with and without helmets for sensible statistics to be created.
Obviously it'll never be perfect (since not all accidents are reported for example), but I'm sure if helmets did offer protection it would show up fairly well.

Bananaman wrote:

Helmets are designed to absorb 12 mph of impact. Thats a significant cushion that anybody involved in an head impact is going to appreciate.

We do not need 'proper statistical analysis' to reason. There are many other, more reliable ways of doing it.

Let's be clear about this.
Helmets are designed to cope with the forces involved in a 12mph accident. That is not the same as absorbing 12mph of impact. Crash forces increase as the square of the speed. A 24mph crash has 4 times the force of a 12mph crash. So at 24mph a helmet won't absorb half the force or 12mph.

http://www.jasmine.org.uk/dogfood/story/article_20.html

Well if you guys are really worrie that 12mph of impact isnt enough you are welcome to where Motorbike helmets.

The fact that cycle helmets conform to minimum international standards set by people like the EU and ANSI tends to make me think its probably enough to be a usefulcushion in most situations bicyclists are likely to experience.

A 12mph cushion does not mean innaffective over 12mph.

The cushion is incredibly important because it lengthens the period of impact:

http://www.independencepolice.org/pdf/C ... July06.pdf

This is useful whatever the speed.

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As well as reducing the force felt, a helemt is likely to distribute that force over a wider energy.

It's really not about the energy, something as small and light as my brake blocks and rims can absorb the deceleration energy from 30-0 in a few seconds without barely heating up.

It's about how big and how concentrated the force is. A hammer can crack a skull, it doesnt have to have a lot of energy, it just applies a short sharp concentrated force to a V. vulnerable area.

Bananaman wrote:It's about how big and how concentrated the force is. A hammer can crack a skull, it doesnt have to have a lot of energy, it just applies a short sharp concentrated force to a V. vulnerable area.

The very same reason a knife proof vest is a much harder proposition to make than a bullet proof one.

Bananaman wrote:Well if you guys are really worrie that 12mph of impact isnt enough you are welcome to where Motorbike helmets.

The fact that cycle helmets conform to minimum international standards set by people like the EU and ANSI tends to make me think its probably enough to be a usefulcushion in most situations bicyclists are likely to experience.

A 12mph cushion does not mean innaffective over 12mph.

The cushion is incredibly important because it lengthens the period of impact:

http://www.independencepolice.org/pdf/C ... July06.pdf

This is useful whatever the speed.

[/url]

Motorbike helmet? The point is I don't like wearing any helmet. I think the risk of me having an accident where a cycle helmet would help is low enough I am prepared to take it.

There are enough examples of helmeted riders being killed that in the unlikely event I was involved in serious accident I'm not convinced it would make any difference. Accidents can be thought of as falling into 3 categories. Slight enough that no serious injuries will be suffered with or without a helmet. Serious enough that you'll be killed whether or not your wearing a helmet. Somewhere in the middle where a helmet might make a difference.

I think the chance of me having an accident in the third group are so low I choose not to wear a helmet. I don't wear one walking down stairs either but people are killed in falls on stairs. If I thought cycling was dangerous I would drive my car to work.

Other peoples assessments of their personal risk depending on their ability, experience and riding environment might differ.

I don't suggest anyone else rides without a helmet just that lawmakers and pressure groups don't prevent me from having the choice.

iaincullen wrote:If I thought cycling was dangerous I would drive my car to work.

Which is exactly what most people do in every country where helmets are considered normal apparel for cycling, even when their commute is easily short enough.

Bananaman wrote:

Some times common sense is a much better guide than stats. Helmets are designed to absorb 12 mph of impact. Thats a significant cushion that anybody involved in an head impact is going to appreciate.

We do not need 'proper statistical analysis' to reason. There are many other, more reliable ways of doing it.

Fine. Just show me the casualty savings...

The point of helmets is to make life safer, i.e., reduce casualties. So before you go about telling people they should wear helmets (never mind "must"...) you should be able to demonstrate useful casualty savings. I have yet to see that beyond speculative anecdotes, and that's really not good enough.

Beyond that, the "significant cushion anybody involved in an head impact is going to appreciate" applies just as much to other things where people bump their heads. Like trips and falls. Last couple of times I've banged my head resulting in pain I could have done without has been around the house, but despite a selection of helmets available I don't wear one around the house. That rather suggests that "common sense" appears to have different answers to the same question, depending on whether or not a bike is involved. On the other hand, "common sense" also says that that must be wrong...

Pete.

pjclinch wrote:

Bananaman wrote:

Some times common sense is a much better guide than stats. Helmets are designed to absorb 12 mph of impact. Thats a significant cushion that anybody involved in an head impact is going to appreciate.

We do not need 'proper statistical analysis' to reason. There are many other, more reliable ways of doing it.

Fine. Just show me the casualty savings...

The point of helmets is to make life safer, i.e., reduce casualties. So before you go about telling people they should wear helmets (never mind "must"...) you should be able to demonstrate useful casualty savings. I have yet to see that beyond speculative anecdotes, and that's really not good enough.

Beyond that, the "significant cushion anybody involved in an head impact is going to appreciate" applies just as much to other things where people bump their heads. Like trips and falls. Last couple of times I've banged my head resulting in pain I could have done without has been around the house, but despite a selection of helmets available I don't wear one around the house. That rather suggests that "common sense" appears to have different answers to the same question, depending on whether or not a bike is involved. On the other hand, "common sense" also says that that must be wrong...

Pete.

Of course if you look at the actual figures, i.e. Cohort studies of hospital admissions, cyclists are way down the tables, often not even appearing as significant when compared to other causes.

Kennedy showed that if all cyclists admitted to a particular group of hospitals had worn helmets the 14 lives would have been saved in 15 years.

However if this is aplied to pedeatrians then 174 lives would have been saved in the same time.

Lets just assume that the helmet would have performed in each case:


So do we save 14 lives by making cyclists wear helmets or 174 lives by making pedestrians wear them?

Beyond that, the "significant cushion anybody involved in an head impact is going to appreciate" applies just as much to other things where people bump their heads. Like trips and falls. Last couple of times I've banged my head resulting in pain I could have done without has been around the house, but despite a selection of helmets available I don't wear one around the house. That rather suggests that "common sense" appears to have different answers to the same question, depending on whether or not a bike is involved. On the other hand, "common sense" also says that that must be wrong...

Just because a helmety might help in other situations does not negate ita efficacy when in a bike accident.

As for cleaiming that a typical accident will involve collisions where a helmet cant possibly help, people make the same argument about wearing safety helmets around heavy lifting equipment or on building sites- 'well if that object which weighs a couple of tonnes and needs heavy lifting equipment falls on me, the helmet isnt going to help.'

The reason why you wear safety helmets in these environments is because people have a habit of leaving loose objects like screwdrivers/bricks sitting in places where they might fall. Its those types of events you are mitigating.

Kennedy showed that if all cyclists admitted to a particular group of hospitals had worn helmets the 14 lives would have been saved in 15 years.

However if this is aplied to pedeatrians then 174 lives would have been saved in the same time.

What exactly does this tell me, other than people tend to walk a lot more than cycle?

Its not death by bike acident that scares me, but brain damage by bike accident:

http://www.helmets.org/stats.htm

Bananaman wrote:

What exactly does this tell me, other than people tend to walk a lot more than cycle?

...... maybe that a large number of deaths to both pedestrians and cyclists are caused by head injuries?

Bananaman wrote:
Just because a helmety might help in other situations does not negate ita efficacy when in a bike accident.

But why do you feel there is need for them to be used in case of an accident on a bike, but not elsewhere, when the accidents elsewhere are at [i]least[/ii] as likely (a) to happen and (b) to cause a serious head injury? It's just a simple case of a double standard: if you want to wear one for your own reasons then fine, but unless you're saying folk should wear them for anything else similarly risky you're coming up with different answers to similar risks on no other basis than if you happen to be on a bike, which is ridiculous.

As for cleaiming that a typical accident will involve collisions where a helmet cant possibly help, people make the same argument about wearing safety helmets around heavy lifting equipment or on building sites- 'well if that object which weighs a couple of tonnes and needs heavy lifting equipment falls on me, the helmet isnt going to help.'

The reason why you wear safety helmets in these environments is because people have a habit of leaving loose objects like screwdrivers/bricks sitting in places where they might fall. Its those types of events you are mitigating.

Exactly: in other words building sites are high risk environments for quite a few different sorts of accidents, major and minor. So all you need to do is prove that people are falling off bikes and whacking their heads more than in what are seen as low risk environments not warranting a helmet (say, around the home and on the streets as pedestrians) and you'll have a good case. But you can't really do that...

Why not promote helmets for use on stairs? They get more people killed every year in the UK than bikes, so why not? This is a serious question. If you can make a case for it being worth it on a bike, why can't you make the same case for using stairs?

Pete.

Bananaman wrote:Its not death by bike acident that scares me, but brain damage by bike accident:

http://www.helmets.org/stats.htm

"the very eminent QC under whose instruction I was privileged to work, tried repeatedly to persuade the equally eminent neurosurgeons acting for either side, and the technical expert, to state that one must be safer wearing a helmet than without. All three refused to so do, stating that they had seen severe brain damage and fatal injury both with and without cycle helmets being worn. In their view, the performance of cycle helmets is much too complex a subject for such a sweeping claim to be made"

That from Brian Walker, the chap who runs Head Protection Evaluations which is the company that tests cycle helmets in the UK.

There remains no good evidence that cycle helmets reduce serious head injuries. Brain injuries are serious head injuries.

It is further the case that plenty of folk get brain injuries from trips and falls, so why not wear a bike helmet when on foot? Being a pedestrian is just as productive of serious head injuries, mile for mile on UK streets, as being a cyclist.

Pete.