This review of the literature examines the evidence for the argument that the effectiveness of road safety measures can be reduced or even negated by changes in road user behaviour following the introduction of new measures. The report begins by looking at the various theoretical explanations that have been proposed in the past, concentrating on the three most influential positions - the theory of risk homeostasis, the risk compensation hypothesis, and the principle of behavioural adaptation. The main part of the report is in the form of a commentary on behavioural response to safety measures, based on an extensive search of the literature and drawing on over one hundred publications dealing with vehicle engineering, the road environment, and the road user. Special attention is paid to the issue of seat belt wearing, a topic that has been much debated over the years. It is concluded that there is little evidence to support the contention that homeostatic, compensatory or adaptation processes routinely act to reduce or nullify the effect of safety measures, and that they do not pose a threat to current road safety practice. An annotated bibliography of the main publications reviewed is given as an appendix to the report. (A)

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