A Reappraisal of Probabilistic Risk Analysis

Its basically an abstract of the article written by John Whitaker from University of Alberta.

In this article, the author come up with critical assessment of fault – tree analysis, concept of probability calculus and concept of acceptable risk to address issues of public safety. To demonstrate the technological hazards’ safety, introduction of probabilistic risk analysis into public debate is done. In this method, fault – tree techniques of reliability engineering are used together with probability theory for calculating the rate of failure for an engineered system. In Probabilistic Risk Analysis, conventional engineering and scientific fields; mechanical engineering, atmospheric diffusion, toxicology etc are used for predicting the consequences of failure. However, the ability of Probabilistic Risk Analysis is questioned whether it is applicable or not because of the serious flaws in analysis’ methodology.  The main flaws that are addressed include inaccuracy, inappropriateness and incompleteness. The probability calculation using fault – tree is not accurate even if all the possible failures could be foreseen and diagrammed. Fault – tree thinking, which is fundamentally linear thinking, is not likely to include many interaction effects. There are several acts and situations addressed in the article that cannot be diagrammed using fault – trees. Due to its concentration technological and scientific causes, fault – tree analysis ignores the human errors/factors which are main cause of system misfortunes. These errors are indicated as Emotional stress, illness, fatigue, etc. The use of Fault – trees is questioned to evaluate system safety in a satisfactory manner because of the system requirements of all failure modes to be expected which is actually not possible. So, for the purpose of illustrating the above flaws, different examples are used from recent accidents. The author has given the reasons for the abandonment of the theory of the probability risk analysis and concentrating on refinement and development of the traditional hazard improvement procedures of mitigation and redundancy.