Special Edition 1999 VOL3Philosophy of SafetyArticle 1 THE CONCEPT OF HUMAN ERROR: IS IT USEFUL FOR THE DESIGN OF SAFE SYSTEMS?

Analyses of industrial accidents have often concluded that 'human error ' is a determining factor in 70-80% of the cases. Furthermore, multiple contributing errors and faults are normally found, because several defenses against accident have been used to protect a hazardous process. Typically, it is also concluded that the 'root cause ' of the accident was a human error on part of a person involved directly in the dynamic flow of events, a pilot, a process operator, or a train driver. Consequently, great effort has been spent to improve safety by better training schemes, by safety campaigns motivating the work force to be safety conscious, and by improved work system design to prevent human errors. In addition, considerable resources have been spent on human error research and comprehensive programs are established to define and categorize human behaviour fragments in terms of errors without any significant success; 'human error ' data bases still do not exist. The concept of human error is very elusive. At a closer look, the frequent allocation of accidental causes to human error appears to be subjective and guided by the tool box of the analyst. This is a simple reflection of the nature of causal analysis and the fact that no objective stop rule exists to terminate the causal back tracking in search of a root cause. The search stops when an event is found for which a cure is known to the analyst