Workload variation, intrinsic risk and utility in a simulated air traffic control task: Evidence for compensatory effects

Air traffic control operations provide a potential example of risk homeostasis theory (RHT) in a non-transportational domain. This paper addresses the issue of whether reductions in intrinsic risk can be negated by behavioural adjustments of operators. Following variations in mental workload, previous studies have suggested that air traffic controllers appear to adapt to changing demands through more active or more effective strategic control of performance. This effortful compensatory control of performance has the consequence of eliminating what would otherwise be concomitant variations in accident loss. However, most of the empirical support for this proposition is taken from observational studies in which the relative occurrence of different levels of workload is not controlled. Using a simulated air traffic control task, a study is reported here in which conditions of low, moderate and high levels of mental workload are presented in equal duration to participants. The findings indicate that number of errors differed significantly across these conditions of mental workload which is contrary to what RHT would predict Evidence is found for a general adaptation (or strategy switching) in response to different levels of workload. This supports earlier work in indicating that behavioural adjustments may not be of sufficient magnitude to restore previously existing levels of safety. However, on a notional measure of extrinsic compensation, participants did respond differently according to workload, thus lending limited support to RHT's prediction that utility and intrinsic risk should act in a multiplicative way to form a statistical interaction. Copyright (C) 1996 Elsevier Science Ltd