Evaluation of workload in air traffic controllers.

This study examined 20 air traffic controllers from the Rome Regional Air Control Centre for three successive work shifts: afternoon (13:00-20:00), morning (07:00-13:00) and night (20:00-07:00). The number of aircraft under control per hour was recorded as index of workload. Recordings involved subjective ratings (mood, physical fitness, fatigue) and objective measures (heart rate, vanillyl mandelic acid excretion, reaction times, critical flicker fusion, oral temperature). In addition, the subjects filled out questionnaires for personality traits (extroversion, neuroticis, anxiety) and behavioural characteristics (morningness, rigidity of sleeping habits, vigourness to overcome drowsiness). The volume of air traffic varied greatly with peaks during the day and low levels at night. Nevertheless, the heart rates of the group members showed quite constant levels in all the three shifts, irrespective of the workload. The same pattern appeared in the controllers' excretion of VMA, which remained high during both day and night shifts, regardless of the reduced workload. The subjective mood and physical fitness decreased similarly, while feelings of fatigue increased on all three shifts, particularly on the night shift. The circadian rhythm of the oral temperature showed a slight modification of the nocturnal depression during the night shift, caused by the state of awakeness and activity. However, the rhythm was not altered in its normal circadian phase, due to the fast shift rotation adopted. The psychophysiological responses were affected by personal characteristics, in particular morningness and ability to overcome drowsiness.