Assessing the variability of air traffic controllers’ workload: A comparative perspective

Controller workload remains the principal functional constraint on air traffic management system capacity, yet its measurement in operational settings is complicated by substantial inter-individual variability that aggregate traffic-based models fail to capture. This case study investigates whether physiological workload differs significantly between certified air traffic controllers (ATCs) exposed to identical operational conditions, a question with direct implications for both safety management and dynamic capacity planning. Three licensed tower (TWR) controllers were monitored during a standardised 50-min heavy-load simulation exercise. During the experiment, physiological stress indicators were monitored, specifically LF/HF, SDNN, and mean RR, in 5-min intervals measured by a single-lead ECG monitor with a sampling frequency of 1000 Hz, supplemented by a 3D accelerator for actigraphy. Simultaneously, photoplethysmographic (PPG) recording was performed in synchronization with a second single-lead ECG for control purposes. Despite identical traffic scenarios, statistically significant inter-individual differences were confirmed for all three parameters ( p ≤ 0.002). Median LF/HF values differed by up to 74% between controllers, SDNN by up to 45%, and mean RR by 5.83%. These differences exceed the magnitudes typically reported between low- and high-workload conditions in within individual aviation studies, demonstrating that individual physiological reactivity, rather than traffic complexity alone, is a primary determinant of operational workload. The findings challenge the current practice of treating airport capacity as a fixed threshold and support the concept of dynamic, real-time capacity management informed by continuous individual physiological monitoring. Practically, the approach enables identification of stress-susceptible controllers, supports personalised shift scheduling, and provides a foundation for deploying operationally compatible wearable ECG monitoring during actual ATC operations.