Theory of barrier crossing

This paper focuses on the analysis of a set of conditions under which tolerated use of a machine can be found. The analysis considers particular violation aspects: the barrier crossing and their associated risks. This operational risk assessment remains qualitative. The Operator experiences an operational risk for crossing a barrier which is a combination of a cost of the crossing, the immediate benefit after a crossing and a possible deficit due to the crossing. Benefits and deficits are related to a compromise between several criteria such as safety and production. For several application domains the approach to analyse barrier crossing will be illustrated.