Costing for ALARP

A key principle for achieving Tolerable Risk under the UK Health and Safety Executive’s (HSE) approach is the reduction of risks to “As Low As Reasonably Practicable” or ALARP. This principle is founded on the ideal of reducing risks to a point of diminishing returns where additional risk reduction would cost “disproportionally” more than the risk reduction benefit achieved. The HSE approach of estimating the degree of disproportionality between the cost and benefits associated with a potential risk reduction measure is a variation of the Cost Effectiveness approach to ALARP Evaluation. A probabilistic cost-benefit analysis method is outlined for evaluating design options and establishing whether the conditions of ALARP are met. This paper demonstrates the value of probabilistic cost-benefit analysis for the selection of a target safety level and also presents an example of its practical application by way of a case history.