Human factors impact on risk analysis of complex systems

This paper discusses the methods and techniques that are applied for including human factors considerations into risk analysis of modern plants. The application of new control design principles and the extensive use of automation have strongly modified the role of operators, who have progressively become supervisors of automatically performed procedures and decision makers in a context of shared management processes. This implies that cognitive functions and organisational factors affect risk analysis much more than behavioural and physical performances. Another crucial issue of human reliability assessment concerns the dynamic nature of human-machine interaction. This feature covers a wide spectrum of real situations, but demands quite complex and extensive data. These considerations favour the development of new and evolutionary techniques which must be confronted with the requirements and needs of different types of risk analysis be carried out for different objectives, such as quantitative risk analysis, safety management, accident investigation, risk-based decision making and risk-based regulations. Advantages and areas of application of different techniques are briefly discussed, without attempting to develop a detailed comparison.