The Effects of Countermeasures for Preventing Vigilance Decrement During Manual and Automated Driving

Using driving mode (manual and automated driving) and countermeasures (chewing gum and auditory-tactile stimulation) for preventing vigilance decrement as experimental factors, this study investigated the effectiveness of chewing gum and auditory-tactile stimulation for preventing vigilance decrement during 2-hour simulated manual and automated driving. The observed reaction times and error rates for the unexpected events revealed the vigilance decrement in the latter half of the 2-hour experiment for both manual and autonomous driving conditions. The countermeasures contributed to mitigating vigilance decrement. The psychological rating on comfort and sleepiness evaluation by KSS during the 2-hour experiment indicated that the chewing gum was more effective than auditory-tactile stimulation. Vigilance decrement was less for the manual driving condition than for the Level 2 automated driving condition with less WWL score of NASA-TLX. The overload explanation applied to the vigilance decrement in manual driving, because the vigilance decrement for the higher workload condition (manual driving without a countermeasure) was more remarkable than that for the lower workload condition (manual driving with a countermeasure). Data of automated driving did not apply to either overload or underload explanation of vigilance decrement, and only the countermeasures contributed to the mitigation of vigilance decrement.