Air traffic controller performance and workload under mature free flight: Conflict detection and resolution of aircraft self-separation

The effects of conflict detection and self-separating aircraft resolution on the mental workload and performance of en-route air traffic controllers were examined. An air traffic control simulator was used to manipulate traffic loads and traffic complexity. A mature stage of free flight was simulated by having controllers monitor self-separating aircraft. Four 30-min scenarios were created to combine moderate (11 aircraft) and heavy traffic loads (17 aircraft) in a 50-mile radius sector with the presence or absence of self-separating and conflicting aircraft. Conflicts (defined as a loss of separation of 5 nm laterally and 1,000 ft vertically) were indicated to the controller by the appearance of a red circle around each of the aircraft invoked. A self-separation event was defined as an evasive maneuver (either altitude or speed change) made by 1 aircraft to avoid a potential conflict with another aircraft. Performance and workload measurements indicated that controllers had difficulty both in detecting conflicts and in recognizing self-separating events in a timely manner in saturated airspace. Controller mental workload also increased, as indexed both by subjective and secondary task measures. Implications for the design of automated tools to support controllers under free flight environments are discussed.