Contrasting safety assessments of a runway incursion scenario: Event sequence analysis versus multi-agent dynamic risk modelling

Recently we compared safety analyses for a runway incursion scenario based on an event sequence analysis, as a key exponent of a traditional risk assessment technique, versus one based on an multi-agent dynamic risk model (DRM), as an exponent of new techniques based on system complexity and variability-based accident models. We found that lower accident risk levels were assessed in the event sequence analysis and we compared various factors contributing to these differences. As the reasons of these differences were not completely understood, this paper sets forth additional analyses towards a better understanding of the relations between conflict recognition and resolution events that may occur in the runway incursion scenario and their relation to accident risk. To this end, such events were recorded in additional Monte Carlo simulations of the multi-agent DRM and a broader set of conditions was considered with agents being in or out of monitoring roles or control loops. The results of the DRM-based study uniquely make clear that the risk is not manifest from the performance of individual human operators and technical systems, nor from the sole relations between human operators and/or technical systems, but only from the totality of the performance and interactions of all human operators and technical systems in the operational context considered. In conclusion, we show that multi-agent dynamic risk modelling has considerable advantages over event sequence-based approaches. KeywordsEvent tree; dynamic risk model; runway incursion; air traffic control; accident risk; human performance; multi-agent