Uncertainty treatment in risk analysis of complex systems: The cases of STAMP and FRAM

Several approaches to systems thinking have been proposed to understand and model complex socio-technical systems and potential accidents, including the System-Theoretic Accident Model and Processes (STAMP) with the associated hazard analysis method System Theoretic Process Analysis (STPA), and the Functional Resonance Analysis Method (FRAM). It is argued that these approaches are suitable for the risk analysis of complex socio-technical systems. The purpose of this paper is to look more closely into this thesis, with a special focus on the treatment of uncertainty and potential surprises linked to the operation of such systems. A key finding is that these approaches may, indeed, reduce the potential for surprises by increasing the system and risk understanding but need to be supplemented with other approaches to adequately support the decision-making on risk issues.