Examining the moderating effect of workload on controller task distribution

Efforts to characterize controller workload - a key factor in limiting en route capacity - have produced mixed results. Subjective workload ratings reveal significant variations in minimum/maximum workload across individuals and show a categorical jump in perceived workload with a linear increase in aircraft count, making it difficult to predict workload limits with increased traffic. In addition, workload seems to be actively moderated by the controller to reduce monitoring tasks during high traffic/workload situations. In this paper, we examine this strategy shift by associating bookkeeping tasks and route/altitude clearances with online workload ratings. Overall, the data suggest that the controllers shed peripheral tasks related to monitoring and bookkeeping as the traffic ramps up and their perceived workload transitions from low to high. Whenever workload reached a maximum, some bookkeeping tasks were delayed and performed in "groups" after the peak traffic subsided.