Modelling operators in accident conditions: advances and perspectives on a cognitive model

In this paper the developments and issues identified in modelling humans and machines are discussed; the possibility of combining them through the system response analyser (SRA) methodology is presented as a balanced approach to be applied when the objective is the study of safe management of systems during abnormal sequences. Attention is then devoted to the human behaviour model implemented or being developed for SRA, and the general frame in which manual and cognitive human activities interact with each other and are carried over by operators in controlling the evolution of transients in complex plants. The model considers two levels of cognitive processes: a high-level decision making, whereby the reasoning about the plant as a whole takes place and a low-level decision making, in which the actual actions of control are carried over. Accounts are also given for the mechanisms of error making and recovery.