ABSTRACT
The human factor gets a bad press. There are two approaches to studying human performance in high-technology hazardous systems: one involves the 'fly-on-thewall' observation of normal activities; the other is triggered by the occurrence of an adverse event. An 'event' is something untoward that disrupts the flow of normal or intended activities and which may, and often does, have harmful consequences. In Human Factors research, at least, there can be little doubt that the dominant tradition is the event-dependent one. Such analyses focus upon the errors and violations that either constitute or contribute to an event. The worse the event, the more intensive the investigation of the preceding decisions and actions. As a result, we have learned a good deal about the varieties of unsafe acts and, to a lesser degree, we know something of the circumstances that can provoke and shape them (Hollnagel, 1993; Reason, 1990).
