Development of safety performance functions (SPFs) to analyse and predict aircraft loss of separation in accordance with the characteristics of the airspace

The occurrence of Losses Of Separation between aircraft in an airspace that could lead to Mid Air Collisions (MAC) is of major concern to Air Traffic Management. This paper uses an innovative approach to develop Safety Performance Functions to predict the occurrence of losses of separation. This will improve the safety conditions under which airlines operate. A data driven approach is used to characterise the Losses Of Separation between aircraft as count data with an excess of zeros and over dispersion. Subsequently, the relationships between the number of aircraft conflicts in a particular route segment and the airspace design and traffic flow characteristics are modelled using Zero-inflated models. Based on the characteristics of the route segment, the distribution that most closely matches observations of the number of conflicts in airspace segments is a Zero-inflated negative binomial probability distribution. It also takes account of the large amount of null values that characterise safety occurrences in aviation.