The paper reviews the significance of the concept of human error in three different applications: task analysis and human reliability estimation, causal analysis of accidents, and design of reliable socio-technical systems. It is concluded that the definition of error is ambiguous and depends on the purpose of analysis. For analysis of accidents, the causes identified depend on the stop-rule applied to terminate the analytical backtracking, and the stop-rule will be different depending on whether the purpose of the analysis is the explain the case, to identify a responsible person, or to improve safety. It is concluded that it can be difficult by a linear causal analysis to identify structural properties leading to such systemic failures which can be caused by adaptive features of the system. Finally, it is shown how adaptation guided by subjective process criteria serves to resolve the degrees of freedom in a work environment so as to remove the need for choice and decision in a stable environment. In a modern, varying environment,however, need for adaptation remains and the inevitable effect of adaptation will be various forms of error. Reliability and safety of socio-technical systems, consequently,depend on boundaries around acceptable performance that are reversible and allow recovery in case of violation. Improvement of safety depends on graceful loss of control and opportunity for learning to recover, rather than on withdrawal of boundaries from present normal operation.
|Number of pages||18|
|Publication status||Published - 1989|