Simulator methodologies for investigating fatigue and stress in the automated vehicle

Research has shown beneficial performance gains from recent advances in automated driving systems. Although these systems show promise for mitigating potentially dangerous effects of driving, namely subjective feelings of stress and fatigue, there are some safety concerns, which may be investigated using simulator methods. This paper examines and illustrates the utility of using a driving simulator to investigate relationships between vehicle automation and driver fatigue. It offers several key criteria that simulator methods should meet in order to establish functional fidelity, so that simulators offer valid measures of subjective fatigue states as well as objective performance changes. The present paper reviews three recent simulator studies from the authors’ laboratory, which investigated the influence that required and optional automation use has on subjective ratings of stress and fatigue, as well as on driver performance. It appears that simulators can and do produce a patterned subjective stress and fatigue response, characterized especially by loss of task engagement. These states are similar to those found in real life driving, and reflect similar cognitive stress processes, including threat and challenge appraisals. Moreover, using a simulator may also capture the potentially damaging effects of fatigue on safety, as evidenced by slowed response to an emergency effect following automated driving. Automation use elicits a state of ‘passive’ fatigue, which can be associated with chronic under-stimulation. In addition, it appears that voluntary control of automation use does not mitigate against fatigue effects. Indeed, fatigue may encourage use of automation. The findings of these studies result in guidelines for traffic researchers in evaluating the effectiveness of simulator methods as well as the influence of automation use on fatigue and stress.