The concept of risk: A decision theoretic approach.

The concept of risk receives increasing attention in traffic safety research and control. However, there is much disagreement about the definition of the concept as well as about its importance. Sometimes, risk is defined statistically to provide a relative measure of safety (accident rates). Sometimes risk is used as a synonym for danger or threat. In this paper, the concept of risk is regarded as a synonym for expected loss, as defined in decision theory. This approach has several advantages. First, in the decision-theoretic model, risk is directly connected with the decisions that are taken by the individual road user. This approach also makes clearer the connection between individual risk and collective risk. Furthermore, the relation between individual behaviour and danger is not over-emphasized. Finally, the model is able to cope with the fundamental aspects of traffic behaviour, such as information sampling and processing, decision making and task performance. (A) This paper was included in the proceedings of a CEC workshop on risky decision-making in transport held at the TNO Institute for Perception, the Netherlands, 9-11 November 1986. (Brown, I. and Janssen, W., editors).