Fietser said:
As E =MVV (MV squared) increasing velocity increases energy exponentially. In other words a wind blowing at 20 mph is 10 times as strong as a wind blowing at 10mph, or getting hit at 20mph involves ten times the force of getting hit at 10mph. I am argueing that cycle helmets are not designed to protect your head in the event of colliding with a motor vehicle. No manufacturer claims any protective effect in such an instance as the materials they are constructed of are not strong enough. Helmet standards these days are below what they were 10 years ago in general. They have got lighter and better ventilated but this is more to do with manufacturers trying to make them more appealing to wear.
My arguement here is that when helmets fail, they fail catastrophically. The energy from the impact is no longer absorbed. Please see
http://www.cyclehelmets.org/mf.html#1045 for a full explannation if you have time. The writer is an internationally acknowledged expert on the subject and works in the helmet testing industry.
I would most welcome your comments.
I had a very quick look at the site - quite informative but I question the motives of thoise behind the site. I am always a bit suspect of sites that push a particular argument and therefore deal with the information on that site with what I hope is a healthy degree of doubt.
I do not think we are in total disagreement. I do not believe cycle helmets offer the claimed 85% and 90% protection that some have claimed - I believe they offer a degree of protection and will, in most circumstances, lessen the extent of injuries. Put simply, I think you are better off wearing a bicycle helmet than not. While I accept there may be some risk that in some circumstances a bicycle helmet might cause injuries that would not have occurred if a person had not been wearing a helmet, I think those risks are worth taking. There is a degree of commonsense in this - if my head is going to hit something, no matter how hard, I'd rather there be something to absorb some of the energy (or shock, as some might express it).
I accept you are correct on the formula for calculating momentum - takes me back to 1st year undergrad physics (when I owned the Peugot referred to in my earlier post - memories of a 6 pack stomach and no mortgage). If I can indulge you by working in metric (the only imperial measures I understand are feet and nautical miles), work through the example you promoted. Assume my head weighs 5000g and I have an impact at 13 mph, which is 22 kph or 6.11 m/s. The momentum of my head at the point of collision will be 186.66 KN (?). Assume, for the sake of the argument, that the helmet will absorb that force and leave my pretty head without injury. Then increase the speed of my head at the point of impact to 27.5 mph, which is 45.8 kph or 12.7 m/s - the momentum of my head will be 806.45 KN. My argument is that, all things being equal and subject to that questionable assumption, my head will receive 619.79 KN less force if I was wearing a helmet in the 27.5 mph collision than if I wasn't, and that has got to be better than copping the full 806.45 KN impact.
I agree it would be good to have a clear scientific study on the pros and cons of wearing helmets. There is not much evidence that I have seen, inclkuding on the site you referred me to, that stacks up from a scientific perspective. However, people have to work with what they have, and the main problem seems to be that each bicycle accident is unique and hard to pin together from a statistical perspective.
I am not convinced by one part of the site refering to what a Court found in a particular case in which the author of that part was a witness for, I assume, for a bicycle helmet manufacturer. The fact that a Court makes a finding that was contrary to the evidence of the author is relevant in determining liabilities between the parties to the proceedings and adds to the common law. But that because a Court makes a factual finding in a particular case before it does not make something factually, or scientifically, correct.
I am a solicitor with extensive litigation experience, both as an advocate and instructing counsel and Queens Counsel, and it is wrong, in my opinion, to use a finding of a Court to prop up a particular perspective in what is a scientific debate. Courts make findings on the evidence they are presented with, and often have to weigh up complex and contradictory evidence from experts in fields that they have no experience. In my experience few judges have scientific qualifications or experience. Courts get it right sometimes and they get it wrong sometimes.
Why does the author of that article seem to think the position he put in his evidence, which was not accepted by the Court in that case, has less worth than the contrary evidence put the experts engaged by the other party? Was the author giving evidence that he actually believed, or was he giving the evidence his client wanted him to give? If the former is true then he can still hold that opinion. If the latter then he is a "gun for hire", and that is soemthing most Courts in Australia are working to weed out of the judicial system by imposing clear rules on the role of experts when giving evidence to a Court.
In summary, I agree that some of the stats are a but suss, but at the end of the day I believe I am better to wear a helmet than not, and I accept it will not protect me from all injuries I might sustain if my head hits something, but I hope it lessens those injuries. If wearing a helmet was utterly useless then I would agree that helmets should not be worn, but whilst there is some benefit I will wear one. It is worth noting that I grew up at a time when no one wore helmets, and I hated wearing helmets when wearing them became compulsory in NSW (a state of Australia, for those who might not know). However, current helmets are more comfortable and seem easier to adjust so they fit correctly.
My 2 cents worth, which might only be worth less than 1 pence elsewhere.
