In October 2007 the Insurance Institute for Highway Safety published a Status Report (PDF: 1MB) complaining about my article “Britain’s Seat Belt Law should be Repealed” (PDF: 0.2MB) (published as “Seat Belt Laws – Repeal them?” in the June 2007 issue of the statistical journal Significance). It went on to denounce all those who invoke the risk compensation effect to question the efficacy of seat belt laws. It concludes: “Don’t believe them, not until they produce credible evidence that people compensate for safety”.
I first produced evidence on the subject sufficiently credible to pass peer review for publication in the Society of Automotive Engineers Transactions in 1982 – “The Efficacy of Seat Belt Legislation” (PDF: 0.2MB). I have revisited the evidence that people monitor their environments for signs of safety or danger, and adjust their behaviour in response to perceived changes, in numerous publications since, including two books: Risk and Freedom: the record of road safety regulation (1985) and Risk (1995).
The idea that people compensate for safety was considered outrageous in 1982, and still is by the Insurance Institute for Highway Safety: “To believe Adams you’d have to believe that people have a certain tolerance for risk and that their levels of risk are regulated by a homeostatic mechanism so that, if forced to “consume” more safety than they voluntarily would choose, people will balance the safety increase by taking more risk. It’s a stretch, isn’t it?”
The “stretch” appears to be now becoming conventional wisdom. It underpins the increasingly popular concept of shared space (PDF: 15KB); Hans Monderman, the Dutch originator of the concept spoke to an enthusiastic sold-out meeting in London’s City Hall this week. And it is even finding its way into government planning guidance in Britain. This quotation can be found in the Department for Transport’s Manual for Streets: evidence and research (PDF: 10MB): “One of the most important variables that needs to be taken into consideration is ‘risk homeostasis’ – the way in which drivers adjust their behaviour to maintain a consistent level of risk. As drivers feel safer they begin to take more risks, whereas conversely, if road conditions make them feel unsafe, drivers are likely to adjust their behaviour to take fewer risks.”