ABSTRACT
The response of a human system or organization to hazards may often be viewed in terms of self-organized criticality. That is, the operating point of the system, in terms of resources, scheduling, work methods, safety barriers, etc, evolves until a balance is reached between competing pressures such as the simultaneous desires for high work productivity and a low probability of accidents. From a safety viewpoint, the system may be viewed as having migrated away from high safety to a point where it is “on the edge of chaos”. Chaos in this case may be defined as a situation where a small perturbation may or may not be absorbed by the system; the outcome is often tragic. At this operating point “on the edge”, the frequency of small incidents already gives an indication that more severe incidents are distinctly possible, even though much less likely to occur. Empirically, a power law relates the frequencies of different severity events.
