Risk assessment A note on F—n curves, expected numbers of fatalities, and weighted indicators of risk

Abstract The paper considers one of the weighted risk indicators used by the Major Hazards Assessment Unit (MHAU) of the Health and Safety Executive in formulating advice to local planning authorities on the development of land in the vicinity of hazardous installations. It is shown that MHAU's ‘Risk Integral’ can be recast into the form of an expected utility function, suitable according to classical decision theory for reaching consistent decisions on risk tolerability. It is also shown that the weightings that the Risk Integral implicitly attributes to multiple fatality accidents are not out of line with those proposed by others.