Predicting risk of near midair collision in controlled airspace

This paper predicts the risk of near midair collisions between airborne aircraft as a function of the type of controlled terminal airspace in which they occur, aircraft velocities, the geometries of approach patterns, and the number of flight operations which arise, end in or traverse these areas. Based on an analysis of near midair collision risk, the paper concludes that air carrier operations by themselves are safer than general aviation operations by themselves in radar-controlled environments such as a Terminal Control Area, but that general aviation operations by themselves are safer in less-controlled than in more-controlled airspace. By far the most risky flight appears to be general aviation aircraft interacting with other general aviation aircraft in positively-controlled environments such as a Terminal Control Area. The authors offer a model which describes the factors that influence near midair collisions and some reasons for a possible explanation of these surprising results.