The risk of an air accident as a result of a serious incident of the hybrid type

Safety in air traffic is a multilayered concept and consists of many safety barriers. The practical side of increasing safety is mainly based on analysing the causes of accidents and incidents. This analysis leads to finding gaps in the safety structure and to developing corrective recommendations in order to eliminate them. In this paper we indicate that this practice is insufficient. Most incidents could transform into accidents with fatalities. The standard method of investigating incidents does not answer the question as to whether safety barrier is permanent or whether it was activated accidentally. This paper proposes a new method for analysing incidents aimed at finding their consequences rather than their causes. This makes it possible to find areas that need improvement. Stochastic, timed, coloured Petri nets were used for the analysis. There are three types of air traffic incidents, distinguished according to events that lead to a transformation of an incident into an accident: causal and temporal. The hybrid case, in which both types are important, has been discussed in detail. The method is useful in evaluating the current level of safety in air traffic. Applicability of this method has been shown on the example of the runway incursion problem. - Highlights: • Current accident investigation procedure is not sufficient. • New method aimed to study incident's conversion into accident was proposed. • The Petri net model of air traffic accident was developed. • Method allows calculating accident probability. • The hybrid case in which both causal and temporal events are important is discussed