ABSTRACT
People are used at critical points in processes to verify that inputs, processes and outputs match planned conditions, and also to capture previous failures before they result in costly incidents. This chapter describes, by means of a case study, one way in which checks can fail. It gives possible reasons for the failure and presents new design principles for reducing the likelihood of checking failures. The interviews and observations of the charging process made it clear that there were substantial deviations from the checking procedures. The main deviations were: The four checks were rarely repeated by a second operator and the barcode identity check was either not carried out at all, or not repeated by a second operator. The expected probability for the failure of the identity check is a product of the four individual failure probabilities, assuming independence between the checks.
