Dynamic reliability and human factors for safety assessment of technological systems: a modern science rooted in the origin of mankind

This paper discusses the needs and requirements for practical implementation of human-machine interaction paradigms in prospective and retrospective analyses for design and safety assessment. The original theories of Hollnagel can lead to a comprehensive and detailed analysis of the "joint-cognitive" system, enabling the identification of root causes of human inappropriate behaviour and the evaluation of potentially complex incidental scenarios. However, the rigorous application of such approaches is sometime too ambitious or simply not possible for the lack of data or for the intrinsic complexity of the modelling architecture. This paper presents two possible ways forward when an overall safety analysis has to be performed for the entire plant and control. On the other hand, when well-defined tasks and specific behaviours need to be studied, the methods proposed by Hollnagel are recognised as the most modern and accurate instruments available.