Modelling lateral spacing and separation for airborne separation assurance using Petri nets

Airborne separation assurance is seen as a promising option for the future air traffic management concept to provide an increase in capacity and flight efficiency while maintaining flight safety. Sofar, studies or expectations are largely based on assumptions about the achievable spacing and separation criteria. These assumptions range from optimistic to reserved, when comparing these separation criteria to currently used radar surveillance-based values. In any case, there is a clear knowledge gap on this subject. Thus, it is important to assess the relationship between spacing and separation distances on one hand and safety on the other hand. This relationship directly affects the effectiveness of airborne separation assurance. The aim of this paper is to address this issue by conducting an accident risk assessment, including a bias and uncertainty assessment and an assessment of risk sensitivity to spacing and separation values. Each stage in the methodology used is illustrated by examples. It is shown that the methodology provides valuable feedback on both the airborne separation assurance operation and the accident risk assessment.