CityCyclingEdinburgh Forum » Debate!

Helmets!

(91 posts)
  • Started 14 years ago by chdot
  • Latest reply from wee folding bike

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  1. wee folding bike
    Member

    I did suggest that you shouldn't use Rivara and Thompson. There was a reason why I advised that you not reference them. Using the same data as Rivara and Thompson you will also find that helmets reduce skint knees.

    Check the para on Problems with the Seattle Study

    They conflate all kinds of injury. I accept that minor scrapes can be reduced but serious injury is increased.

    You're assuming there is no down side to wearing a helmet. This is not supported. Evidence shows that the incidence of serious injury increases where helmet wearing has been made mandatory.

    Opinion is not very strong evidence. I used to use a helmet, I read more about it and found it was a poor choice so I moved on.

    Are you disputing the drop in mileage in Australia? Some of the information on that comes from road side surveys and some comes from the national census. They show the same pattern from different sources. This is a good thing to have in evidence.

    Australian figures being 20 years old does not invalidate them. Helmets were actually made to a higher standard then.

    Here are some more recent things.

    Flaws in Cochrane

    UK report from 2005

    Magazine article about helmets and decline in standards over the last 20 years.

    And consider this. Every time you see a face cream ad on TV there is a wee line about how 7 out of 10 women in a sample of 80 through it had some effect. I drive Volvos and for years their USP was safety. They would put some data in their about collisions at 30 mph, SIPS, crumple zones and so on. There is big money to be made selling helmets. If there was any good evidence in favour of them we would see it but we don't. I had a look at Specialized's web page. Their helmets are known to be the best for standards compliance. I didn't find any claims about their effectiveness outwith compliance with standards. They talk about weight, ventilation and comfort but they do not try to sell their magic hat safety device on evidence of safety. Why would that be?

    Posted 14 years ago #

  2. wee folding bike
    Member

    chdot,

    Can you tell me the flaw in Australian data which shows a decrease in miles cycled and an increase in serious head injuries per mile?

    Assumptions about the beneficial effect of helmets impinge on me. Why should these assumptions not need to be supported?

    The Australian law came in 20 years ago. How would we find more up to date information? Why does the age invalidate it?

    You then accuse me of assumptions. Young, inexperienced cyclists are over represented in collisions on a per mile basis. Those who have been cycling longer have learned tricks like looking for moving wheels because it's easier to tell what a vehicle is doing that way. If nothing else Darwin would say that if you have been cycling a long time then you are fit.

    Left turning lorries will not be mitigated by a magic hat. As I have mentioned before they are rated for a 12 mph impact on a flat surface.

    Cycling is safe, roads are a reasonably safe environment. Cycling is safer than not cycling.

    Posted 14 years ago #

  3. steveo
    Member

    http://xkcd.com/386/ ;)

    any way... No i fully accept there was a down turn in the cycling mileage in Aus but i have also pointed out on two separate occasions now that there is a similar drop in the UK which is unexplained by either group and points to a potential flaw in the reasoning of the study.

    My quote wasn't from Rivara and Thompson it was from J Adams and M Hillman both from the anti helmet group! They agree that a helmet reduces the damage from knocking ones head. I agree the methodology employed by Rivara et al is flawed.

    Helmets were made to an arguably higher standard but were less comfortable and made the user more hot this is a very important point when considering the location. Would the results be the same now? I doubt it, but again there is "nothing in evidence" from either side.

    "You're assuming there is no down side to wearing a helmet. This is not supported. Evidence shows [citation needed] that the incidence of serious injury increases where helmet wearing has been made mandatory."

    What evidence! The studies posted on both sides are rubbish, inconclusive and vague. This is all based on opinion. In fact your own exibit suggests this is non sense
    "Results:There is little evidence in UK from the subset of road collisions recorded by the police corresponding to the overall benefits that have been predicted by the results of a number of published case controlled studies. In particular, no association could be found between differing patterns of helmet wearing rates and casualty rates for adults and children."
    http://www.informaworld.com/smpp/content~db=all?content=10.1080/15389580590931590

    Posted 14 years ago #

  4. wee folding bike
    Member

    steveo,

    I had a look and can't see it but are you actually claiming a 40-60% drop in cycling in the UK in the early 90s? Are you saying that the drop in Aus cycling was not related to helmet laws? The BMJ would not agree nor would anyone else I've read and I'v read a lot on this.

    Did you mean the "Cochrane review OF Rivara..." rather than BY?

    That older standard was better, go have a look. Snell is better than the EU or current US standard. We don't even know how many current helmets meet the standard because it doesn't have the same quality control as the old one.

    Then you rubbish all the data before you cite a paper which says that helmets don't work. Apply Occam's razor and what do you get?

    Have you an alternative explanation for why serious injuries increase with helmet use? I can give you a correlation and cause do you have that?

    Posted 14 years ago #

  5. steveo
    Member

    Lets have a quick round up so every one is clear:

    Anti-helmet contention 1: Helmets cause accidents to be exacerbated.
    "You're assuming there is no down side to wearing a helmet. This is not supported. Evidence shows that the incidence of serious injury increases where helmet wearing has been made mandatory."
    Support: The Aus Study.

    Anti-helmet contention 2: There is no link between helmet wearing and the out come of an accident.
    "You also appear to assume that a magic hat will reduce your chance of serious injury. This has not been demonstrated. "
    Support: UK report from 2005, http://www.informaworld.com/smpp/content~db=all?content=10.1080/15389580590931590

    Which is it? Either there is no link between helmet use or there is.

    Now for the Aus theory, the mandating of cycle helmets has meant that the instance of injury has increased and the cycling mileage has dropped. What is the critical mass theory?
    "Mandatory cycle helmets means that fewer people will cycle. Fewer cyclists makes it more dangerous for those of us who cycle."
    So could the reported 40-60% drop in cycling volumes have any impact on the injury rate since now there are less cyclists and drivers are even more oblivious to them? Seems to contradict your earlier assumption that mandated helmet use was to blame for the increase in accidents.

    My point is this: The results of ALL the studies are inconclusive and despite being reported as gospel they are just opinion.

    And just to muddy the waters, the critical mass theory is not really supported by the department for transports annual statistics.
    Cycle Volume (100 million vehicle kilometres) Change in cv Casualty Rate (KSI) Change in CR
    1990 53 88
    1991 52 98.4% 81 92.5%
    1992 47 91.6% 84 104.1%
    1993 40 84.7% 95 112.3%
    1994 40 100.2% 100 105.1%
    1995 41 103.1% 96 96.1%
    1996 41 98.4% 93 97.0%
    1997 41 100.1% 88 94.7%
    1998 40 96.9% 84 95.2%
    1999 41 103.2% 78 92.9%
    2000 42 102.0% 67 85.5%
    2001 42 101.8% 63 95.0%
    2002 44 104.2% 55 87.8%
    2003 45 102.2% 53 96.3%
    2004 42 93.1% 55 102.8%
    2005 44 105.4% 53 97.0%
    2006 46 104.7% 53 98.9%
    2007 42 91.6% 60 114.6%
    2008 47 111.7% 54 89.5%

    This will need copied to a spreadsheet to be of any use to any one.

    Posted 14 years ago #

  6. steveo
    Member

    Oh and before i forget:
    "Have you an alternative explanation for why serious injuries increase with helmet use? I can give you a correlation and cause do you have that?"

    Correlation<>Causation!
    http://en.wikipedia.org/wiki/Correlation_does_not_imply_causation
    http://www.statistics-help-online.com/node50.html

    Posted 14 years ago #

  7. wee folding bike
    Member

    I think you lose points for the correlation != causation thing. I know that and did not confound them. If this was Slashdot you might get a +1 for it.

    Do you want to ask about the causation?

    In s similar round up you first started with the equation for kinetic energy and didn't bother to reply to that one when it turned out I knew the equation too and understood how it related to helmets. Then you rubbished the numbers for the fall in cyclist numbers numbers in Australia. They came from good independent sources and showed the same pattern. The pattern is repeated in New Zealand and Canada I don't think you're quibbling about that anymore or do you still think there was some spooky action at a distance effect in the UK?

    Then you said you had an opinion that helmets would help but you rather sold the jerseys on that one since you now contend that nobody can tell.

    You're quote mining for your two points at the top of your recent post. The quotations you use for contention 1 and 2 seem to be different sides of the same thing. The quote you use for number 2 doesn't seem to say what you think it says. Helmets not improving the outcome does not mean they have no effect.

    I think I see where your confusion on critical mass and Aus results comes from. It's not just the number of injuries, it's the type which changed. Diffuse injury results from rotational impacts and is much more serious. This is one of the errors made by Rivara et all. They don't define injury.

    It's difficult to do rotation injury experiments on people but it has been done on dummies and monkeys. I'll supply the numbers if you like.

    So are you just left with the increase in serious injuries since you seem to have dropped the rest of it?

    Posted 14 years ago #

  8. steveo
    Member

    I may well have been quote mining but only becuase i want you to clarify since your arguments are contradictory and yes they are different sides of the same thing that is the point. You may understand this but the studies i've now looked at do not show causation merely correlation. I've also provided a plausible reason for the increase in injury, ie the critical mass effect which you have shrugged off. Equally the i've never seen any where state that the point of the critial mass was to change the type injury.

    I've never disputed the drop in numbers merely the cause. There was no legislation introduced in the UK therefore that is clearly not the case but a 25% drop was recorded just the same its not a huge leap to say that 40% drop in Aus may be a statistical anomaly that happened to occur at the same time as the legislation was introduced, after all we don't know what other factors were involved, one we do know is the end of the recession which generally means people have petrol money so jump back in the car. (Correlation)

    My opinion on the Helmet has not changed and my point remains there is no PROOF either way, i'm happy with that and with my earlier contention that the helmet is a very small inconvenience that i'm happy with. The anti-helmet position to me seems to be preaching though and i'd say that it is here that proof is required not opinion based on manipulated statistics, which is what this boils down to.

    As for the previous thread go check it was locked before i could not respond. Any way yes the helmet is under speced at 15mph but hopefully one could slow before hitting the ground, buggered on long steep down hill but still adequate on a normal road and i'm sure your aware sacrifices between utility and safety are common.

    I suspect that we two could go back and forward on this for ever but maybe some one else can will look at this and make up there own mind either way and not take the rubbish information out there as gospel.

    Posted 14 years ago #

  9. wee folding bike
    Member

    If you want to find the causation then google for diffuse axonal injury. Or have a look here at point 5:

    http://www.cyclehelmets.org/papers/c2022.pdf

    So do you contend that a matching post legislation fall in cycle numbers in NZ and Canada is merely a correlation too? I haven't seen any papers which dispute the cause but you could try looking.

    You might also like to check what happened to usage figures in Ontario when they stopped enforcing the law... can you guess what happened?

    Do you require proof of efficacy before you use a helmet or are you using common sense?

    The 12 mph/20 km/h takes no account of forward velocity. It's the speed of the average adult head after falling down.

    Gospel I don't do. I do use a trailer religiously when I take number 4 son out in it on a Sunday.

    Posted 14 years ago #

  10. steveo
    Member

    All i see is a similar drop in a country with no legislation, what conclusion would you draw?

    So DFI is up after helmet use is up? The obvious counter to that is that people are not experiencing TBI because they have their safety hat on. Much like whiplash was very uncommon before seatbelts were mandated.

    This is interesting and perhaps answers the criticisms that the rated speed for helmets is too low. No account is made for forward velocity becuase it is not necessary.
    "the surface of the road is almost parallel to the direction the motorcyclist moves in so only a small component of his velocity is directed perpendicular to the road while he is riding"
    "a perpendicular impact against a flat steel anvil at 5 m/s (11 mph) might be about as severe as a 30 m/s (67 mph) oblique impact against a concrete surface or a 30 m/s perpendicular impact against a sheet metal car door or windscreen."
    http://en.wikipedia.org/wiki/Motorcycle_helmet#Standards_testing

    Posted 14 years ago #

  11. SRD
    Moderator

    I still need more time to read the injury data, but Steveo is certainly correct that we cannot assume that a drop in cycling is caused by helmet law, unless we ask every single person who stopped cycling! Social science is like this -- many, many intervening (or preceding) variables which cannot be controlled for, and are often hard even to identify. This is why in the Canadian study, I said it was not enough to compare two provinces, but that we needed to look at actual numbers of helmets worn per cycling population etc. Otherwise the comparison might not be comparing 'like with like'.

    Posted 14 years ago #

  12. wee folding bike
    Member

    The one time I was hit by a car the speed of me and the road being different resulted in a few stitches. I hit the ground, her car hit the back wheel and nearside crank but the only thing I hit was road. That was in the days when I did wear a helmet and it didn't help one bit.

    Increase the radius of your head when it hits the ground and you get a bigger rotational effect.

    You're not going to get an increase in speed rating. They aren't sold on that basis. They aren't even sold on safety.

    You have a problem with the safety in numbers effect in Aus. How would it change the distribution of types of injury? Do you have a mechanism for that? I do.

    Posted 14 years ago #

  13. steveo
    Member

    Does this not fit under the same category as "the helmet saved my life" part of the cycle helmets site, basically discounting anecdotal evidence? I don't know the circumstances of your particular accident and so can't comment directly.

    The Motorcycle crash standards would apply in part to bicycle standards in as far as the force applied is similar in direction if not in magnitude.

    I don't want an increase look at the link. The motorbike standard is for 4–7 m/s the bicycle standard is for 5.5 if its good enough for a motorbike doing 60 then it'll do for me doing 15.

    Did you deliberately misrepresent the bicycle standard or did you not understand the way the applied force works?

    Posted 14 years ago #

  14. wee folding bike
    Member

    Just commenting on how the mismatch in speed did have an effect. I was on a main road, nurse came out of a side road. It was 14/02/96 and I've still got the scar to show that the helmet didn't help.

    Try this:

    http://www.cyclehelmets.org/1182.html

    They find that rotation does occur.

    If "Un-helmeted post-mortem human surrogate data" means what I think it means then it's not a job I'd want.

    Not sure what you mean by misrepresent. Do you mean the 20 km/h?

    Posted 14 years ago #

  15. kaputnik
    Moderator

    Of course, helmet is better than no helmet for the purposes of protecting ones self from jakey-launched ice;

    BBC news article

    Posted 14 years ago #

  16. Kirst
    Member

    Well, yes.

    Look, helmets offer some protection in some circumstances, no protection in other circumstances and might make things worse in yet other circumstances. Now, can we get back to discussing something less pointless?

    Posted 14 years ago #

  17. Min
    Member

    Sums it up pretty well Kirst!

    Hope that guy is okay.

    Posted 14 years ago #

  18. gembo
    Member

    looks like Kirst has summed it up neatly (as much of the data is as old as me and biased - tho personally I found it interesting). Would I be correct then in concluding from Kirst's handy precis that helmet wearing therefore has a slight edge for the individual tho it might in some extrapolation of certain hypotheses lead to less people cycling which in turn may lead to cycling being more dangerous? Time for the wee red dot to close this string?

    Posted 14 years ago #

  19. Kirst
    Member

    Excuse me while I go and hit my head off a wall.

    Posted 14 years ago #

  20. wee folding bike
    Member

    Kirst,

    Well there are also lawyers trying to use them against cyclists, there are safety campaigners who reckon that if we all wear a magic hat they have ticked the box for sorting out cyclists - at no cost to anyone else, there is the concept of blaming the victim instead of controlling the cause... and probably a few other things.

    Posted 14 years ago #

  21. gembo
    Member

    lawyers trying to use walls against cyclists, typical

    i hope kirst was wearing her helmet when she hit her head off the wall, scottish govt., would take a dim view otherwise

    Posted 14 years ago #

  22. Kirst
    Member

    It's all right, my walls are made of cheese.

    Posted 14 years ago #

  23. wee folding bike
    Member

    I just had some Wensleydale with cranberries. It's OK but I'd prefer something with blue bits in it.

    Posted 14 years ago #

  24. wee folding bike
    Member

    On the topic of lawyers I used to cycle past this sign every day in 2006.

    Posted 14 years ago #

  25. wee folding bike
    Member

    gembo,

    No, you can't conclude that helmets have a slight edge for the individual.

    Posted 14 years ago #

  26. gembo
    Member

    Foldy, it wasn't me concluding anything (I was just inaccurately reading Kirst's summing up which caused her to hit her head off her cheese walls but if it was hard cheese I am still concerned about her not using her helmet - I favour manchego with some membrillo).

    All that can be concluded is that no matter what the data does or doesn't say, people will stick to their opinion. It is not a topic on which it is possible to be neutral.

    Posted 14 years ago #

  27. wee folding bike
    Member

    I would conclude more than that but then I know I'm not wedded to one side. I changed at least once already.

    Danish Blue.

    Stilton can't be made in Stilton.

    Posted 14 years ago #

  28. gembo
    Member

    yeah but you wouldn't want to be described as neutral? or would you? I once said I was neutral in the RangersVCeltic aggro but the teacher I was talking to, said (humourously) yeah but neutral kafflik or neutral prod?

    Posted 14 years ago #

  29. wee folding bike
    Member

    Thistle... but only because I have a friend who goes and I have my name on a sponsored brick in the stand.

    And I don't like football.

    Posted 14 years ago #

  30. gembo
    Member

    Used to stay next door to Firrhill for Thrills. NEver saw much football tho you would come across the odd half brick. My team DUFC about to plummet to relegation dogfight I predict.

    Posted 14 years ago #

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