Three horizontal distances determine risk judgments about conflict between two aircraft: (a) the distance between the crossing of the aircraft trajectories and the first aircraft to reach that point; (b) the distance between the two aircraft when they are horizontally closest; and (c) the distance between the two aircraft when their growing vertical distance reaches 1,000 feet. This paper proposes a model of conflict judgments in air traffic control (ATC). Two experiments tested whether the variables in the model reflect what controllers do. In the first experiment, 125 certified controllers provided risk judgments about situations in which the model variables were manipulated. The second experiment compared a population of certified controllers with a population of ATC students in order to investigate the relationship between the model and expertise. Results showed that, in both experiments, the model accounted for 44% to 50% of the variance in risk judgments by certified controllers but only 20% in judgments by ATC students. In the second experiment, the model described experts better than novices. There were major individual differences in the predictive power of the model as well as in the contributions of the three variables. It can be argued that an individual-differences approach is required when investigating the strategies involved in conflict judgment in ATC. Implications of these findings for the development of ATC training programs and user-friendly interfaces with conflict detection devices are discussed.
Abstract