Safety Science 19 (1995) 217-225 Self-explaining roads Jan Theeuwes, Hans Godthelp TN0 Human Factors Research Institute, P.O. Box 23, 3749 ZG &ester-berg, The Netherlands zyxwvutsrqponm Abstract This paper discusses the concept of a structurally safe traffic system. The crucial question is how potential errors occurring in traffic can be reduced by revising the layout of the road environment. Two considerations play an important role: inherent safety and self-explaining properties. Inherent safety refers to the reduction of potentially dangerous encounters. Traffic systems having self-explain- ing properties are designed in such a way that they are in line with the expectations of the road users. The in this paper discussed “Self-Explaining Road” (SER) is a traffic environment which elicits safe behavior simply by its design. 1. Introduction One of the major problems of road traffic is its level of unsafety. It is commonly estimated that over 90% of the traffic accidents are related to human error. Because better education, information and enforcement only have a marginal effect on accident reduction, it is crucial that the road and vehicle environment is adjusted to the human capacity limitation. Safety should be considered as a system property to be built into the road and vehicle environment (see e.g., Godthelp, 1990; Roszbach, 1990; Twisk, 1991). The crucial question is how design principles can reduce the probability of an error when executing the traffic task. Two aspects play an important role: inherent safety and self-explaining properties. Inherent safety refers to the reduction of potentially dangerous encounters. Traffic systems having self- explaining properties are designed in such a way that they are in line with the expectations of the road user. The so-called “Self-Explaining Road” (SER) is a traffic environment which elicits safe behavior simply by its design. In recent years, the TN0 Human Factors Research Institute has studied several aspects of Self-Explaining Roads. For example, Riemersma ( 1988) investigated how drivers inter- nally represent different road categories. Theeuwes (1989, 1990, 1991a) investigated the role of drivers expectations on search strategies in traffic. Recently, Theeuwes and Godthelp ( 1992) applied the principles of enduring a safer road environment on rural 80 km/h roads, and inferred a list of design criteria for the development of SER. 092%7535/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDlO925-7535(94)00022-O