Driver stress and fatigue are common problems that may impact safety. This study focuses especially on the threat to safety posed by driving in monotonous environments which elicit both subjective tiredness and performance impairment (Thiffault & Bergeron, 2003). It is important to distinguish between states of stress and fatigue, and traits that may predispose the driver to stress.
Subjective stress and fatigue state responses can be assessed using the Dundee Stress State Questionnaire (DSSQ: Matthews, Campbell, Desmond, Huggins, Falconer,
& Lucy, 1999), which evaluates stress states and arousal on the dimensions of Task Engagement, Distress, and Worry. The driver's general proneness towards stress may be assessed using the Driving Stress Inventory (DSI: Matthews, Desmond, Joyner, & Carcary, 1997). States of fatigue may also be measured using cerebral blood flow velocity (CBFV), assessed by transcranial Doppler sonography (TCD). Previous research in this laboratory has shown that the temporal decrement in vigilance performance is accompanied by declining CBFV and that CBFV responses to demanding tasks predict subsequent vigilance (Reinerman et al., 2007).
The aim for this study was to investigate whether the utility of CBFV as a diagnostic index of stress and fatigue generalized from traditional vigilance paradigms to the task of driving. Consistent with previous research, driver performance deteriorated over time and the drive elicited increased distress and loss of task engagement. Additionally, CBFV decreased with time on task and the DSI fatigue proneness scale predicted lower task engagement during driving.
On the whole, results of the present study offer support to the supposition that CBFV has some potential as a valid diagnostic index to predict fatigue while driving but further research is needed in this area.