Graphic representations of the causal flow of accidents have been very important tools in industrial risk management for decades. Causal trees, event trees, and cause-consequence-charts have been applied extensively to manage the complex flow of events to consider during post event analysis to understand accidents and during predictive risk analysis for design of protective systems. Such graphic representations have been very effective in creating an overview of complex occurrences and for communication of assumptions and findings within a risk analysis and design team. Representational schemes have quite naturally been focused on the propagation of the effects of `abnormal' events such as technical faults and human errors through the functional structure of a technical system, because a substantial part of the development has been focused on industrial process plants. It has, however, been increasingly acknowledged that organisational and social factors should be included in risk analyses leading to the development of tools such as MORT - the Management Oversight and Risk Tree (Johnson, 1973). Recently, the authors have found that the present fast technical and social changes call for a further development of these graphic tools. It has become increasingly necessary to consider highly adaptive socio-technical systems for which deterministic, causal models developed for technical installations become inadequate. Furthermore, due to the fast pace of change of technology and financial conditions, emphasis is increasingly on proactive risk management strategies replacing reactive methods based on analysis of accidents in the past. The paper presents a set of graphic representations, the authors have found useful in this situation, to structure analyses of hazardous work systems and to identify the interactions in a socio-technical system shaping the landscape in which accidents may unfold themselves. Also, and not the least, these representations serves as a vehicle in support of discussions during field work and system auditing. The authors do not pretend to present a full developed and tested tool, but to illustrate a line of development that we find important for reasons discussed below. The idea of "AcciMapping" to structure the socio-technical system behind an accident and to indicate the preconditions, the functions on the different system levels involved and how they have contributed to the developments has been adopted in "Lessons from Longford: The Esso Gas Plant Explosion", (Hopkins, 2000). (A)
Abstract