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The short-term effect of verbally assessing drivers' state on vigilance indices during monotonous daytime driving

Institut für Experimentelle Psychologie, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf; Daimler AG; Research and Development, GR/PAP, 50-G024, D-71059, Sindelfingen, HPC; Wilhelm-Schickard-Institut für Informatik, University of Tübingen, D-72076, Tübingen
Transportation Research 07/2013; 14:251-260. DOI:10.1016/j.trf.2011.01.005

ABSTRACT To investigate the effects of verbal assessment of subjective driver state on objective indicators of vigilance state during a monotonous daytime drive, a real road driving study was conducted. During a 4-h drive participants’ subjective state (sleepiness, inattention,
monotony) was assessed every 20 min by an investigator accompanying the drive. The
assessment procedure consisted of roughly 1 min of verbal interaction. Physiological
indicators (EEG alpha spindle rate, blink duration, heart rate) revealed a significant
improvement of vigilance state during the communication episode as compared to a
pre-assessment baseline. The activation persisted for up to 2 min following the end of
the verbal interaction. Reaction times supported these findings by indicating a significant
decrease after the communication. The P3 amplitude of the auditory event-related potential
did not show any consistent results. It can be concluded that a short verbal assessment
has positive effects on drivers’ vigilance state. However, these effects persist only for a very
limited time. The implications of these findings for the frequency of verbal assessment
during experimental studies and for the use of verbal communication as a fatigue countermeasure are discussed.

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