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• The effects of vibration amplitude on driver drowsiness were investigated. • The onset of drowsiness varies with the vibration frequency and increases with amplitude (0.05–0.2 m/s 2 r.m.s.). • Vibration-induced drowsiness contours were developed, based on this study and the authors’ previous research. • The findings have critical implications for road safety and transport vehicle design. Introduction: Drowsiness is a significant cause of crashes in the various transport industries, including automotive, aviation, and rail. Our previous study investigated the differential induction of drowsiness in drivers caused by specific whole-body vibration (WBV) frequency ranges, with an amplitude of 0.2 m/s 2 r.m.s. The present companion study investigates the effects of different vibration amplitudes on the induction of driver drowsiness. Method: This study includes two experiments. In the first, 15 participants engaged in six 1-hour sessions of simulated driving, experiencing WBV at frequencies of 0 Hz (no vibration), 1–4 Hz, 4–8 Hz, 8–16 Hz, 16–32 Hz, or 32–64 Hz, with an amplitude of 0.1 m/s 2 r.m.s. In the second experiment, another group of 15 participants underwent three 1-hour sessions of simulated driving, exposed to WBV at frequencies of 0 Hz, 1–4 Hz, and 4–8 Hz, with an amplitude of 0.05 m/s 2 r.m.s. Results: As indicated by driving performance, reaction time evaluations, and subjective reports, the extent of drowsiness decreased with decreasing vibration amplitude. Practical Applications: Based on the results of this and our previous paper, discrete contours for WBV-induced drowsiness were developed. These contours will assist the transport industry in reducing the incidence of vehicle crashes caused by drowsiness.
Zhang et al. (Thu,) studied this question.