Autonomic nervous system and subjective ratings of strain in air-traffic control.

The paper is aimed at studying the perceived strain in professional air-traffic controllers both through self-evaluation and physiological indicators from the autonomic nervous system (ANS). The number of aircraft to be monitored was the main independent variable and could evolve at random within 1 and 10. Five ANS variables were recorded continuously in 25 participants while they handled real traffic: skin potential, skin conductance, skin blood flow, skin temperature and instantaneous heart rate. The tonic level of each physiological variable was averaged to match the times spent monitoring a constant number of aircraft. After the session, participants reacted in compliance with the NASA-TLX rating scale. Subjective ratings and physiological values were closely correlated to the number of aircraft, especially when data were standardized thus reducing inter-subjects differences in baseline levels. Results provide objective information to prevent air-traffic controllers from overloaded situations as well as to improve passengers' safety.