Eight air traffic controllers carried out exercises using a TRACON II Air Traffic Control (ATC) Simulator. After a training and familiarization day, each controller carried out four simulation exercises, two low and two high traffic load. His performance during each exercise was recorded by the simulator, a self-assessment questionnaire for fatigue and a test of event-related potential (ERP) were applied and a sample of saliva was taken for cortisol analysis before and after each experimental session. The NASA-TLX was completed after each exercise and a test of alpha-rhythm attenuation was carried out at the start and end of each day. The NASA-TLX is the (US) National Aviation and Space Authority Task Load Index, a widely used self-assessment method, which combines six major aspects of workload to form a general index. It is widely used in Aerospace, Aviation Air Traffic Control and other studies of dynamic human operator activity.

Controllers rated the ‘mental demand’ scale of the NASA-TLX higher on the first, training, day. During measured exercises, their rating of their own performance was higher during the high traffic exercises, although their measured performance contradicted this assessment. The alpha-rhythm attenuation test showed no significant variation during the study, although subjective self-assessment of sleepiness and fatigue (different concepts) showed a clear circadian rhythm, in particular the ‘post-lunch dip’. After the final session on day 2, however, sleepiness was reduced, while fatigue increased.

EEG spectral analysis of the delta, theta alpha and beta frequencies. During the learning day, an increase of theta was observed from low to high traffic, consistent with the suggestion that this is related to learning. (During the second, measured day, more high frequency EEG was observable in high load exercises.)

The Event-Related Potential, particularly P300, showed a significant post-exercise reduction after the high-traffic scenarios. Salivary cortisol showed a strong circadian component. In addition, although eight subjects are not really sufficient to establish a significant difference, controllers appear to form two groups, one showing high cortisol values, the other low values. The higher cortisol group performed better and rated their workload higher during the training day. During the measured exercises, however, the high cortisol group had better performance in low workload, but showed a strong deterioration of performance in the high-load exercises.

The high cortisol group slept more, and felt more tired on waking. Apparently, they were more ‘fatigueable’. Cortisol analysis, Event-Related Potentials and fatigue/sleep questionnaires are recommended for further use in Real Time (RT) simulations.

Because the TRACON/Pro simulator can be used with keyboard or mouse/pointer control, the controller need not speak during the exercise, which greatly facilitates EEG studies. Further studies are now being carried out using more EEG channels, to investigate inter-hemispheric differences as potential measures of the completion of training.