Risk Compensation and Bicycle Helmets
Ross Owen Phillips,?Aslak Fyhri, and 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.
The full paper is here:
A comment from Cyclehelmets.org
Researchers in Norway have looked into possible reasons why there is no good evidence of reduced injury benefit in countries that have enacted cycle helmet legislation despite studies showing that helmets have the potential to reduce injuries.
It was found that the cyclist population 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 bene?cial is that they disproportionately discourage the safest cyclists. Discouraging cyclists with the lowest accident risk increases the overall average risk per cyclist and thus any potential safety intervention, such as a helmet, has no (or possibly even a negative) net benefit.
The researchers conclude that this shift in the cycling population caused by helmet laws is a more likely explanation of why laws do not work than risk compensation (whereby cyclists take more risks because they feel better protected).