Abstract
The purpose of this study is to detect driver's low arousal level at an early stage of drowsiness to prevent traffic accidents. This paper deals with a method to evaluate sleepiness by using electroencephalogram (EEG). Possibilities of detecting a low arousal level, as well as timing of giving warning, are studied based on the correlation between deterioration in driving ability and a driver's EEGs. Driving simulator is used in tests. These tests reveal that lumped á waves obtained from EEG are closely related to deterioration in driving ability, indicating the possibility of warning a driver at an early stage of drowsiness.