Of critical importance: Toward a quantitative probabilistic risk assessment framework for critical infrastructure

Abstract

Critical comments can be made to the current risk assessment framework for critical infrastructure used in The Netherlands: the Dutch National Risk Assessment (DNRA). The DNRA uses a qualitative approach to risk assessment, based on, for example, ordinal risk scoring and the risk matrix. Even though qualitative risk assessment methods are internationally popular, there is no scientific evidence that a qualitative approach to risk assessment actually works. In the case of the DNRA, the main points of criticisms relate to the usage of a subjective concept of risk, dependency on subjective risk experts, the use of risk matrices and the absence of decision rules. To combat these criticisms, this article proposes a quantitative probabilistic risk assessment framework for critical infrastructure based upon four design principles, that a methodologically justified risk assessment method for critical infrastructure should meet. The proposal made for the quantitative risk assessment framework uses a Bayesian approach, a standardized measure for negligible risk in the form of a yearly mortality probability of 10−6, and Disability Adjusted Life Years to quantify human life years for social cost–benefit analysis. Finally, the proposed quantitative method is demonstrated in a case study.