Subjective and objective fatigue dynamics in air traffic control

Fatigue is a longstanding issue in air traffic control (ATC), closely associated with shift work and time-related factors. However, the dynamics of fatigue across morning, evening, and night shifts in an area control center (ACC) remain largely underexplored. This study examined sleep duration and fatigue progression across different shift types. Both objective (three-minute Psychomotor Vigilance Task, PVT-B) and subjective (Stanford Sleepiness Scale, SSS) measures were conducted at the beginning, middle, and end of each shift. Results indicated that pre-shift sleep duration was shortest before night shifts, likely increasing sleep pressure and reducing alertness during the window of circadian low (WOCL). Subjective fatigue remained stable throughout morning shifts but increased towards the end of evening shifts, reflecting circadian influences. Night shifts exhibited peak fatigue during the WOCL, driven primarily by circadian rhythms rather than task load. Objective measures revealed a mid-shift decline in performance, with only partial recovery in the latter half of night shifts. Compared to day shifts, night shifts resulted in significantly higher fatigue levels, underscoring the critical role of circadian rhythms in fatigue dynamics. These findings highlight the need for targeted fatigue mitigation strategies that address circadian vulnerabilities and irregular sleep patterns in ATC shift systems.