Bicycle helmets – A case of risk compensation?

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swansonj
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New academic study on risk compensation

Postby swansonj » 21 Mar 2011, 8:51pm

I get sent the contents of the journal Risk Analysis as part of the day job and noted the following abstract (but unfortunately I can't justify the day job paying to access the whole paper):

Risk Compensation and Bicycle Helmets
Ross Owen Phillips, Aslak Fyhri, Fridulv Sagberg

This study investigated risk compensation by cyclists in response to bicycle helmet wearing by observing changes in cycling behavior, reported experience of risk, and a possible objective measure of experienced risk. The suitability of heart rate variability (HRV) as an objective measure of experienced risk was assessed beforehand by recording HRV measures in nine participants watching a thriller film. We observed a significant decrease in HRV in line with expected increases in psychological challenge presented by the film. HRV was then used along with cycling pace and self-reported risk in a field experiment in which 35 cyclist volunteers cycled 0.4 km downhill, once with and once without a helmet. Routine helmet users reported higher experienced risk and cycled slower when they did not wear their helmet in the experiment than when they did wear their helmet, although there was no corresponding change in HRV. For cyclists not accustomed to helmets, there were no changes in speed, perceived risk, or any other measures when cycling with versus without a helmet. The findings are consistent with the notion that those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster. They thus give some support to those urging caution in the use of helmet laws.

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hubgearfreak
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Re: New academic study on risk compensation

Postby hubgearfreak » 21 Mar 2011, 9:07pm

that's interesting, but i think it's measuring the wrong things. i'd even go as far as to say irrelevant.

what someone does with regards to risking their own bones is entirely up to them.

it's how those in their cars and vans alter their behaviour around the vulnerable (or percieved to be less so) that's the crucial thing, and sadly ignored in that abstract :(

snibgo
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Re: New academic study on risk compensation

Postby snibgo » 21 Mar 2011, 9:42pm

I wouldn't say it is irrelevant. My own "risky" behaviour includes not being properly aware of other road users and the daft things they might do. I routinely wear a helmet, so this research implies I might take greater care when bareheaded.

But, like Hubbers, I'm more concerned about what other road users do around me. I'd like to see a study comparing the effects of (a) ordinary clothing, (b) ordinary clothing with one or both of hi-viz and helmet, (c) lycra etc.

I bought some lycra gear at Lidl's, and it's almost getting warm enough to wear it, so I'll be able to do my own trials.

Ellieb
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Re: New academic study on risk compensation

Postby Ellieb » 21 Mar 2011, 9:55pm

I agree with both of the above, but this does not seem like great research to me in any case. For a start:

a: It is based on only two rides of 400m
b: It doesn't make any comparison of the speeds between the two cases. (ie did those who normally ride with a helmet ride faster when wearing it than those who were not habitual wearers.)
c: It ignores the fact that those who wear helmets regularly may be more risk averse & thererfore be more likely to slow down without a helmet.
d: It is surely significant that those who don't normally wear a helmet did not appear to speed up when they put a helmet on. This is surely significant as well but does not seem to be commented on.
Last edited by Ellieb on 22 Mar 2011, 3:41pm, edited 1 time in total.

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meic
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Re: New academic study on risk compensation

Postby meic » 21 Mar 2011, 9:58pm

I am convinced by the idea of risk compensation and consider taking a fall at 40mph down a hill in my full motorcycling armour to be quite safe (unless I get tangled with any thing solid like a motorbike) compared to coming off in shorts and t-shirt, OUCH!
I ride accordingly.

However a silly little plastic cycling hat doesnt fill me with any feelings of security at all.
Yma o Hyd

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hubgearfreak
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Re: New academic study on risk compensation

Postby hubgearfreak » 21 Mar 2011, 10:31pm

Ellieb wrote:d: It is surely significant that those who don't normally wear a helmet did not appear to speed up when they put a helmet on. This is surely significant as well but does not seem to be commented on.


that's easily explained. those that don't normally wear them don't do so because they know the helmets to be worthless. so putting something on that's known to be worthless would, as you'd expect, make no difference.

those that normally wear them are of the belief that when they haven't got one on they're more vulnerable

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Bicycle helmets – A case of risk compensation?

Postby Vorpal » 3 Nov 2012, 10:10am

The Norwegian Government has funded a number of transport studies through the programme Risk and Safety in Transport (RISIT). I will be posting some other studies, as they all appear to be well-researched and interesting studies. I've emailed one of the authors of this one asking for permission to share the full text. But in the meanwhile, here are abstract, conclusions, and a link to a download. I think that the link requires a subscription, but as I have one, I can't be certain what others can access.

Abstract:
Several studies have shown that bicycle helmets have the potential of reducing injuries
from accidents. Yet, no studies have found good evidence of an injury reducing effect in
countries that have introduced bicycle helmet legislation. Two of the most promising
explanations for why helmet laws do not work as intended are risk compensation and
shifts in the cycle population as a response to the law.
The present article investigates whether the lack of effect of helmet wearing laws is due
to risk compensation mechanisms or population shifts (i.e. discouraging cyclists with the
lowest accident risk, and thereby increasing the overall average risk per cyclist). A random
sample of 1504 bicycle owners in Norway responded to a questionnaire on among other
things helmet use, bicycle equipment use, accident involvement, cycling behaviour and
risk perception. Data were analysed by using structural equation model (SEM). The results
show that the cyclist population in Norway can be divided into two sub-populations: one
speed-happy group that cycle fast and have lots of cycle equipment including helmets, and
one traditional kind of cyclist without much equipment, cycling slowly. With all the limitations
that have to be placed on a cross sectional study such as this, the results indicate
that at least part of the reason why helmet laws do not appear to be beneficial is that they
disproportionately discourage the safest cyclists.


Conclusions:
The results show that the cyclist population in Norway broadly consists of two sub-populations: one training-oriented
speed-happy group that cycle fast and have lots of cycle equipment including helmets, and one traditional, old-fashioned
kind of cyclists without much equipment, cycling slowly. In the latter group it seems like the most careful and those who
feel unsafe wear helmets.
The results of this study indicate that the lacking effect of helmet legislation most likely has to do with a population shift
effect, in which the introduction of mandatory bicycle helmet wearing will lead to a decrease of traditional cyclists in the
cycling population, who do not have much accidents anyway, whereas the speed-happy helmet- and equipment using cyclists
will remain. Reduced cycling will quite clearly have negative social health consequences (Cooper et al., 2008; Gidske
et al., 2007; Hendriksen, Simons, Garre, & Hildebrandt, 2010). Reduced cycling may also lead to a reduction in what is called
safety in numbers, i.e. the fact that the fewer pedestrians or bicyclists there are, the higher is the accident risk for these road
users (Jacobsen, 2003).
The results give less support to a risk-compensation explanation, in particular because the speeding behaviour of the
speed-happy group is more connected to other types of equipment than to bicycle helmets. The helmet is more or less just
one element in the total equipment package. So it is not because of the helmet that these cyclists ride fast; they use all the
equipment (including helmets) because they want to ride fast.
However, as these results are based on cross-sectional data, further studies using longitudinal data on cycling behaviour,
equipment use and risk perception is needed in order to resolve some of the issues concerning causal directions between the
variables.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

Steady rider
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Re: Bicycle helmets – A case of risk compensation?

Postby Steady rider » 3 Nov 2012, 10:37am

Robinson 1996 report shows data for children in NSW. The equivalent number of injuries for pre law level of number of cyclists increased from 1310 (384 head + 926 other injuries) in 1991 to 2083 (488 head + 1595 other injuries) in 1993

Robinson DL; Head injuries and bicycle helmet laws; Accid Anal Prev, 28, 4: p 463-475, 1996
http://www.cycle-helmets.com/robinson-head-injuries.pdf

I think risk compensation may be only one factor in the above result.

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Re: Bicycle helmets – A case of risk compensation?

Postby Vorpal » 3 Nov 2012, 10:45am

The main conclusion is that population shift is a bigger factor than risk compensation. There are a couple of follow-on studies, one of which was authored with the same Ross Phillips who authored the helmetted/unhelmetted risk compensation study published last year.

http://www.sciencedirect.com/science/ar ... 7512001169

Abstract:
It has been suggested that the safety benefits of bicycle helmets are limited by risk compensation. The current article tests if previous helmet use influences the response to helmets as a safety intervention. This was investigated in a field experiment where pace and psychophysiological load were measured. We found that after having removed their helmets, routine helmet users cycled more slowly and demonstrated increased psychophysiological load. However, for non-users there was no significant change in either cycling behaviour or psychophysiological load. We discuss the implications of these results for a hypothesis of risk compensation in response to helmet use. We also show that heart rate variability is a promising measure of psychophysiological load in real-world cycling, at least in situations where there is limited physical demand.


Conclusions:
Whatever the dynamics and confounders of risk compensation, the most important issue for policy-makers and planners remains whether helmet use should be encouraged or not. The results from this study show that helmet users cycle more slowly when the helmet is taken away. It also indicates that the lack of helmet results in a certain emotional experience. It is uncertain if this is a lasting effect. The possibility remains that helmet laws may increase cycling speed among certain cyclists, while discouraging those who find helmets unpractical from cycling. From a methodological perspective the observed differences in HRV measures are of value for other studies looking at effects of risk reducing interventions in other situations where it is possible to control amount of physical load. Using such measures is a practical and economical way of learning more about the role emotions play in decision making in hazardous situations.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

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meic
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Re: Bicycle helmets – A case of risk compensation?

Postby meic » 3 Nov 2012, 11:40am

This does imply that if cycle helmets were banned there would be a decrease in cycling fatalities and injuries!

Unfortunately it would not last long though. Unless some speed freaks decided that without helmets they would give up riding all together. Didnt the Dutch have similar ideas a little while ago?
Yma o Hyd

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Re: Bicycle helmets – A case of risk compensation?

Postby Steady rider » 3 Nov 2012, 6:50pm

http://www.cycle-helmets.com/P885.pdf

may provide extra details.

Vorpal
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Re: Bicycle helmets – A case of risk compensation?

Postby Vorpal » 3 Nov 2012, 7:32pm

Steady rider wrote:http://www.cycle-helmets.com/P885.pdf

may provide extra details.


That's the one I meant when I said,
helmetted/unhelmetted risk compensation study published last year
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

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Re: Bicycle helmets – A case of risk compensation?

Postby Steady rider » 4 Nov 2012, 10:47am

Risk Compensation and Bicycle Helmets
Ross Owen Phillips,∗Aslak Fyhri, and Fridulv Sagberg
http://www.cycle-helmets.com/P885.pdf

Bicycle helmets – A case of risk compensation?
Aslak Fyhri, , Torkel Bjørnskau, Agathe Backer-Grøndahl
http://www.sciencedirect.com/science/ar ... 7812000587

Sometimes small differences can affect the results, eg car braking in the wet on diferent tires.

Helmets add about 200 - 400 grams or perhaps more for a full face helmet to the effective head mass. probably adding about 5%-8%. Detailed investigations regarding riding stability may be worth while. i think there are detailed studies for motorcyclists on riding stability but only general studies for cyclists and not helmet specific, Jones, Bicycle Science details, not sufficient to establish to what degree helmets have an effect. In the case of braking and going over the handlebars this case can be precisely calculated. In many other riding modes a precise calculation cannot be provided or that is how it seems. Add in effects of risk compensation and together the hopeful benefits of helmets may not be the end result on a population basis. Add on top the health consequences of helmet laws, safety in numbers and the outcome is negative for both health and safety,

mikeymo
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"Bicycle helmets – A case of risk compensation?"

Postby mikeymo » 20 Jun 2020, 2:27am

Last edited by mikeymo on 20 Jun 2020, 10:23am, edited 1 time in total.

millimole
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Re: "Bicycle helmets – A case of risk compensation?"

Postby millimole » 20 Jun 2020, 8:22am

I'm not sure if they've answered their own question, but it's valuable all the same.
Fast riders will always wear helmets anyway, and slower -(safer) riders are discouraged by helmets (when laws are enacted).

What they seem to fail to address is whether the faster riders are wearing helmets because of fashion, or if those riders feel they can ride fast due to the helmet.

I might also be tempted to question the equicalance of slow being safe. Slow can be nervous and unsure.
Leicester; Riding my Hetchins since 1971; Audaxing on my Dawes; Riding to work on a Decathlon Hoprider