For safety-critical operations in the nuclear and chemical industries, Petri nets have proven to be useful for the compositional specification of appropriate accident risk assessment models. For air traffic operations, the development of such model is more challenging due to the high distribution of and complex interactions between the multiple agents involved. The specific problems are: A) Need for a hierarchy from low level Petri nets to the complete Petri net; B) Duplication of arcs and transitions within a low level Petri net; C) Cluttering of interconnections. The chapter develops adequate solutions for each of these problems. The solution approaches are first explained graphically, and next formally. The approach developed is illustrated for an air traffic operation example.

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In this paper we consider Nash equilibrium solutions in dynamic, games with exponential cost criteria. Feedback risk-sensitive Nash equilibrium solut,ions are derived for two-person discrete-time linearquadratic nonzero-sum games. Both the complete state observation case and the partially observation case are covered.

With increasing traffic there often are environmental and economical reasons to optimise Simultaneous Converging Instrument Approaches (SCIA) without sacrificing the high safety levels realised in air traffic. One of the well known safety issues of SCIA is the risk of a mid air collision due to a double go around. The aim of this paper is to show through a working example that there is a clear advantage to accomplish the safety protection through support of advanced accident risk assessment methodology. In this paper such methodology is applied to a specific example of SCIA at Schiphol airport. Comparison of the obtained results against FAA established SCIA criteria shows that there are situations in which these FAA criteria are not met, while the collision risk is not higher than for other situations that satisfy these criteria. The implication for Schiphol airport is that a specific change can be introduced as being risk neutral. The implication for other busy airports with converging runways might be that there is room to develop new or improved SCIA without compromising safety.