Several methodological approaches have been specifically developed in other areas for the analysis of occurrence and consequences of human errors. They are suitable for the analysis of safety risks based on the contribution of human fac-tors. In spite of the efficiency of these approaches in terms of safety improve-ment, they have some limits. They do not take into ac-count the contribution of human operator to the management of the unknown situations and the lack of knowledge of operator. This contribution discusses a predictive model based on trial-and-error process for generate the possible human behaviour coping with unknown situations.