Air Traffic Control Complexity and Safety

Abstract

“Air traffic control (ATC) complexity” can be defined as the interaction between air traffic and the sector characteristics through which this air traffic flies. Research indicates that complexity is the prime determinant of the air traffic controller's workload. Research has attempted to define and classify complexity variables that have been used to assess the capacity of en route airspace in Europe and North America. Such variables can also be used to assist in ATC sector design by highlighting those complexity factors that can lead to high workload and potentially risky scenarios for the controller. With the use of a structured interview technique, a study analyzed these ATC complexity variables for their impact on controller workload and safety. Seventy-nine air traffic controllers were interviewed about the factors that affected their workload. These controllers were based in 14 area control centers in Europe, including those of high complexity, such as Maastricht, Netherlands, as well as in nine centers in Asia, one in Africa, and Mumbai, India, a region with major traffic growth in recent years. On the basis of these interviews, a taxonomy of more than 50 complexity variables subdivided into 11 major groupings, such as traffic mix and entry and exit points, has been developed. In addition to rating of the impact of the individual complexity factors to assess their effect on airspace, interactions between complexity variables were deduced from the interviews. These interactions enable assessment of the factors that add to layers of complexity for controllers. Such a taxonomy can assist airspace planners in designing sectors that avoid complex ATC situations. How the impact of such complexity factors can be investigated in sector design is outlined.