Incorporating human dependent failures in risk assessments to improve estimates of actual risk

Abstract

This paper outlines ongoing research into incorporating Human Dependent Failures (HDFs) in risk assessments. It describes how dependent failures are dealt with for both hardware failures and human errors. Problems associated with including HDFs in task analysis and risk analysis techniques, in an either qualitative or quantitative assessment, are illustrated using a simple process engineering example. In particular, the ways in which event tree analysis and fault tree analysis are able to cope with multiple human actions are examined. Certain methodological issues are raised concerning the identification, representation and quantification of HDFs in risk analyses. Recent research indicates ways to enhance risk analysis and current Human Reliability Analysis (HRA) techniques for coping with HDFs within a risk assessment framework. Current developments and suggestions for future research into HDFs are presented for each of these areas.