Risk Homeostasis

A Theory about 

Risk Taking Behaviour

Common Misunderstandings

1. Risk homeostasis and Risk Compensation

 

The theory of risk homeostasis I originally labeled “risk compensation theory” in 1972, 1974 and 1976. And in choosing that label I clearly made a mistake. It was an unfortunate choice because of the confusion it has created in recent years.[1],[2],[3],[4].

 

The term “risk compensation” is, strictly speaking, incorrect because, according to risk homeostasis theory, road users are not expected to compensate for risk in such a way as to reduce it to zero, but instead to show some form of behavioural adjustment in response to what might be called “changes in intrinsic risk.” These are the changes in risk that would theoretically occur under the condition that road users would not alter their behaviour in the face of interventions, for instance, if they did not decide to drive faster when cars are made more crashworthy and slower if roads are narrowed.

 

However, risk compensation theory says that they will alter their behaviour. Thus, labels such as “conservation of risk” or “safety compensation” might have been more appropriate, but unfortunately, these do not clearly point at the mechanism of homeostasis. Quite a number of authors have referred to my work using the terms “risk compensation” or “danger compensation,” and some have made a distinction between “risk compensation” and “risk homeostasis” as if compensation were a soft-pedalling or watered-down version of homeostasis.[5] They suggest that compensation might be partial and "fall short of homeostasis, that is, complete compensation." That is not what I meant. The term homeostasis refers to a mechanism, a process that aims at providing an output that matches the target output, not to a constant output. Misunderstanding of the notion of homeostasis gives rise to comments such as: "The extreme views of risk homeostasis have attracted little support".[6]

 

Despite the relative unfamiliarity of the word “homeostasis,” the term “risk homeostasis” seems to be preferable to “risk compensation,” “risk conservation” or “safety compensation.” Another possible label would be “the theory of behavioural compensation in response to changes introduced in intrinsic risk.” But, although correct, this title is rather awkward. At any rate, all four labels are merely different names for the same fare.[7]

 

Ever since the publication of an OECD report in 1990 the term “behavioural adaptation” to technological safety interventions has become increasingly popular[8] although the possibility of the accident rate being controlled by a homeostatic process had already been suggested in a much earlier OECD report.[9] A problem with "behavioural adaptation" is that it does not spell out to what criterion, to what end effect, this “behavioural adaptation” is supposed to operate, nor whether it has a positive of negative effect on safety, nor why it should occur at all.[10] The term “risk homeostasis” would seem more appropriate.



[1]Wilde, G.J.S. (1974). Wirkung und Nutzen von Verkehehrssicherheitskampagnen: Ergebnisse und Forderungen - ein Überblick. Zeitschrift für Verkehrssicherheit, 20, 227-238.

[2]Wilde, G.J.S. (1972). General survey of the efficiency and effectiveness of road safety campaigns: Achievements and challenges. Proceedings, International Conference on Road Safety Campaigns. The Hague, October 19-20.

[3]Wilde, G.J.S. (1978). Theorie der Riskokompensation der Unfallverursachung und praktische Folgerungen für die Unfallverhütung. Hefte zur Unfallheilkunde, 130, 134-156.

[4]An unfortunate choice, also because it may be confused with the phenomenon of "risk compensation," which refers to extending extra pay for workers in hazardous jobs ("danger money").

[5]Grayson, G.B. (1996). Behavioural adaptation: A review of the literature. Report 254. Crowthorne, U.K.: Transport Research Laboratory.

[6]Hedlund, J. (2005). Risky business: safety regulations, risk compensation, and individual behavior. Injury Prevention, 6, 82-89.

[7]Wilde, G.J.S. (1994) Target Risk [first edition].Toronto, PDE Publications, p. 29-30.

[8]OECD (1990). Behavioural adaptations to changes in the road transport system. Paris: Organization for Economic Co-operation and Development; Road Transport Research.

         [9]Wilde, G.J.S., L’Hoste, J., Sheppard, D. and Wind, G. (1971) Road Safety Campaigns: Design and Evaluation. The Use of Mass Communications for the Modification of Road User Behaviour. Paris: OECD; Also published in French: Campagnes de Sécurité Routière, Calcul et Evaluation.

[10]Rudin-Brown, C.M. and Jamson, S.L, Eds. (2013) Behavioural adaptation and road safety. Boca Raton, CRC Press.