A Method for Rating the Severity of Runway Incursions

Risk is a function of the probability of an event and the severity of the consequences of that event. Any discussion of issues of risk in surface operations must include a valid and reliable measure of the severity of the outcome of runway incursions. This paper describes an automated method for rating the severity of the outcome of runway incursions. This model was developed using the same criteria and decisions that experts currently use to determine the severity of an incursion. The model assigns a severity rating based on the information contained in the preliminary report of the incident. This includes: the geometry of the situation that resulted in the incursion and the closest proximity (horizontal or vertical), visibility, type aircraft, and whether or not (and characteristics of) the avoidance maneuver. The initial validation was conducted by comparing the model’s assessment of 307 runway incursions to the assessment conducted by a panel of subject matter experts in the FAA Runway Safety Office. In 92% of the incidents, the model matched the group’s ratings (of three levels of severity). Patterns of discrepancies are well defined and discussed. Ongoing validation efforts are also described. Finally, possible applications to losses of standard separation in the air are explored.