On Communicating the Uncertainty of Risk

Abstract

There are now a number of guides to help civil engineering professionals communicate risk. However the available techniques to deliberate on, identify and manage risk still require development especially for dealing with uncertain open world ‘wicked’ problems with low probability and high impact as confirmed by a recent high level government review in the UK. A well known, but not well understood, paradox at the heart of practical life is that on the one hand we routinely make risky practical decisions perfectly well but on the other hand our judgements about statistically testable risks are sometimes significantly in error. We maintain that managing uncertainty is the key; that classifying uncertainty as either aleatoric or epistemic is insufficient; and that standard probability theory has to become an interval measure which we characterise as an ‘Italian Flag’. A framework is proposed, based on evidence theory, through which all types of uncertainties about risk can be expressed in a way which is simpler to communicate, easier to understand and hence is a basis for improved risk management