ACCIDENT RISK AND DRIVER BEHAVIOR

The concepts of risk compensation and risk homeostasis are often used to describe or to explain drivers' tendencies to react to traffic syst em changes whether in roads, vehicles, weather conditions or in their own skills. However, it is important to distinguish between the genera l phenomenon and mechanisms underlying it. This paper first points out that to understand the basic mechanisms it is necessary to split acci dents and exposure into smaller entities to arrive at basic units of e xposure which also represent fundamental driver tasks. Risk-related be haviour should be considered at several hierarchical levels with diffe rent mechanisms to produce 'risk compensation'. At a high level, trip decisions modify populations at risk in different circumstances, somet imes attenuating, sometimes amplifying population risk differences. At a low level of vehicle control and guidance in real dynamic traffic s ituations, simpler control mechanisms which result in behavioural adap tation can be identified. All these effects influence the end result o f accident risk as separate mechanisms. Copyright (C) 1996 Elsevier Sc ience Ltd