A Novel Experimental Strategy for Validating Human Failure Probabilities in Risk Assessment

Human error is a significant contributor to process accidents today. Human failure probabilities are mostly based on the judgment of experts; this makes conforming their validity difficult. In this paper we propose a novel experimental strategy for validation of human failure probabilities. Our strategy is based on the time taken by human participants to bring a plant to a normal state, in response to an abnormal event (like disturbance in flow rates or temperature). The inability of human participants to bring the plant within normal limits is considered to be human error (failure). The response times taken by human participants give the measured human response-time probability distribution. The response-time distribution enables us to validate the human response times and, consequently, human failure probabilities. We report the results obtained from a study of 72 participants controlling an industrially important process.