This paper discusses the concept of `sustainable safety', first proposed in 1992, which has become the basis of Dutch road safety policy. According to this concept, road design should consider the limitations of human functioning, which show various human errors. Three types of error were distinguished: (1) strategic-tactical-operational, at the different hierarchical levels of the traffic task force; (2) knowledge-rules-skills, at different task performance levels; and (3) perceptual and judgement errors in information processing. The sustainable safe environment was to be designed to prevent these errors from occurring, and distinguished three sources of error. Thus a sustainable safe environment would prevent unintended infrastructure use, interactions with high speed or directional differences, and insecure behaviour. Tables in the paper present some characteristics of these different road categories. There were several difficulties in proceeding from these design principles to design specification. Various experiments show that people indeed use an implicit road classification, and adapt their expectations to the perceived road class on which they are driving. Several road sections have been implemented that at least approximate to the sustainable safe design specifications.
Abstract