Tiredness and visual reaction time among nighttime cab drivers: a roadside survey

The present roadside survey seeks to elucidate the incidence of tiredness among nighttime cab drivers by comparing self-assessed level of tiredness with the results of a simple visual reaction test. Attempts to separate various forms of fatigue from sleepiness are not made, as it appears less important in studies of everyday traffic than in experimental investigations. One-hundred-and-twenty cab drivers of vacant cabs were stopped by the police on a major highway just outside the city of Copenhagen. Eighty drivers declared themselves rested, 38 tired, and 2 very tired. The reaction test showed considerable individual variation, but subdivision of the drivers according to level of tiredness demonstrated a statistically significant and uniform difference throughout the night (p < 0.0001). One self-assessed tired driver was reclassified to the group of very tired based on the questionnaire and reaction test. The investigation indicates that accidents due to "driver asleep" would be expected among the three (2.5%) very tired cab drivers. The questionnaire and visual reaction test turned out to be complementary in the present study and are both useful implements for future roadside surveys of tiredness in nighttime traffic.