DMAS_4 _3_ - Risk Analysis DOI...

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Risk AnalysisDOI: 10.1111/j.1539-6924.2011.01589.xRisk Compensation and Bicycle HelmetsRoss Owen Phillips,Aslak Fyhri, and Fridulv SagbergThis study investigated risk compensation by cyclists in response to bicycle helmet wearing byobserving changes in cycling behavior, reported experience of risk, and a possible objectivemeasure of experienced risk. The suitability of heart rate variability (HRV) as an objectivemeasure of experienced risk was assessed beforehand by recording HRV measures in nineparticipants watching a thriller film. We observed a significant decrease in HRV in line withexpected increases in psychological challenge presented by the film. HRV was then usedalong with cycling pace and self-reported risk in a field experiment in which 35 cyclist vol-unteers cycled 0.4 km downhill, once with and once without a helmet. Routine helmet usersreported higher experienced risk and cycled slower when they did not wear their helmet inthe experiment than when they did wear their helmet, although there was no correspondingchange in HRV. For cyclists not accustomed to helmets, there were no changes in speed, per-ceived risk, or any other measures when cycling with versus without a helmet. The findingsare consistent with the notion that those who use helmets routinely perceive reduced riskwhen wearing a helmet, and compensate by cycling faster. They thus give some support tothose urging caution in the use of helmet laws.KEY WORDS:Bicycle; heart rate variability; helmets; risk compensation1. INTRODUCTIONBicycle helmets have the potential to reducehead injuries according to several cross-sectionalcase-control studies.(1,2)Other evidence suggests thatthe introduction of helmet laws does not result inclear safety effects.(35)One explanation given forthe ambiguous effects of helmets is that cyclists per-ceive the risk of injury to be lower when wearing ahelmet, and instinctively compensate by cycling moreaggressively, according to the theory of risk compen-sation.(4,6,7)There is some support for this idea, witha recent study of children running over an obsta-cle course observing significant risk compensation inresponse to helmet and wrist-guard wearing.(8)How-ever, there is no published evidence of risk com-pensation by cyclists in response to bicycle helmetwearing.Address correspondence to Ross Owen Phillips, Gaustadalleen21, 0349 Oslo, Norway; [email protected]The concept of risk compensation has a firmbasis in the domain of driver behavior research,which typically describes how perceived risk influ-ences various safe driving behaviors. In this tradition,risk perception is often only inferred from observedbehavior or accident rates—it is rarely measured.This contrasts with research in the risk perceptiontradition, in which survey methods are often usedto try to explain the components of risk perception,but behavioral outcomes are rarely measured.(9)Themost convincing evidence for or against risk compen-sation would need to be gathered using a research

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