Definition and Analysis of a New Risk Priority Number Concept

Abstract

Risk Priority Numbers (RPNs) are a powerful qualitative method for discovering and prioritising critical issues in early design phases. They have become very popular in particular as a tool in automotive or software Failure Modes, Effects, and Criticality Analysis (FMECA). However, it has been shown that the existing RPN concept is seriously flawed. This paper presents a theoretical approach towards a new RPN concept, called the Improved Risk Priority Number (IRPN), which is based on a sound model of risk and can be used with equal ease, but does not suffer from the shortcomings of the existing RPN concept. A particular example from a railway application is discussed.