The complexity of failure: Implications of complexity theory for safety investigations

Complexity theory suggests that we see performance as an emergent property, the result of complex interactions and relationships. This can clash, however, with what stakeholders see as legitimate and normal in accident investigations. When systems fail, it is still common to blame components (e.g. human errors) and when they succeed spectacularly, to think in terms of individual heroism (e.g. the A320 Hudson River landing). In this paper, we lay out the contrast between a Newtonian analysis of failure that can be recognized in many efforts at safety analysis and improvement. It makes particular assumptions about the relationship between cause and effect, foreseeability of harm, time-reversibility and the ability to produce the "true story" of an accident. With inspiration from complexity theory, failures are seen as an emergent property of complexity. We explore what that means for safety science and work towards a post-Newtonian analysis of failure in complex systems. © 2011 Elsevier Ltd.