Effects of light and heavy workload on air traffic tactical operations: A hazard rate model

This paper introduces a class of event history analysis used to examine how the operations of an air traffic controller change under light and heavy traffic workload. The analysis begins by assessing the hazard rate, h(t), of a transition (or spell) between the controller's communication and flight progress activities. h(t) is the instantaneous rate of going from one state (i.e. an activity of communication or flight progress) to another in a unit of time, given that the controller has been in the first state until time t. Results indicated that the spell distribution closely followed a Weibull distribution, a prerequisite for this analysis. The results also indicated that h(t) was more likely regulated by time in heavy than in light workload conditions, and that under heavy workload, indirect speech from the planner controller would decrease the h(t) for communication to flight progress spells. The results suggest that a dynamic model for the analysis of air traffic control may be necessary, and that the implications of using modular automation may not be straightforward. This technique may be of general use to examine temporal regularities in operating real-time control tasks.