RSAmodellering

RSA-modellering refers to a family of modelling approaches used to assess reliability, safety and availability of complex systems. It integrates probabilistic methods to evaluate how often systems fail, how long they take to recover, and how these failures affect overall performance. The term is widely used in safety-critical industries, but there is no single standard; RSA modelling encompasses multiple techniques and viewpoints.

Common formalisms include Markov chains (including continuous-time Markov chains), reliability block diagrams, fault tree analysis, event trees, Petri nets, and Bayesian networks. These models can quantify metrics such as mean time to failure, mean time to repair, system availability, failure probabilities, and sometimes safety integrity levels or risk metrics. The choice of formalism depends on system structure, data, and the questions asked.

A typical workflow involves defining system boundaries and interfaces, identifying components and failure modes, assembling data on failure rates, repair times, and maintenance practices, and selecting an appropriate modelling approach. The model is built and solved or simulated to produce outputs. Sensitivity analyses and uncertainty quantification are often performed, with validation against historical data.

RSA modelling is applied in aerospace, nuclear power, rail transport, oil and gas, automotive, and process industries, as well as in software and safety analyses. It supports maintenance planning, spares optimisation, safety and regulatory compliance, and risk-informed decision making.

Challenges include limited or biased data, simplifying assumptions, modelling rare events, incorporating human factors, and ensuring results are transparent and usable for decision makers.