Abstract

Using the database of vehicle accidents and traffic density on the Korean highway network during the last two years(1999-2000), the present study evaluates the relation between the hourly distribution of the relative risk (relative hourly probability of accidents corrected for traffic density) on the highway vehicle accidents and the circadian rhythm of sleepiness. It is found that the relative risk (for all the 3 categories: # of cases, # of the wounded, # of deaths) in the hours of 00-06h and 22-24h is significantly higher than in the rest of the hours, and that the relative risk is the highest during the 02-04h, then 04-06h / 00-02h, and then 22-24h. It is noticeable that in the category of # deaths, the relative risk of 02-04h(the peak) is more than 14 times higher than that of 12-14h(the trough). While based on based on the total accidents of all causes, the hourly distribution of the relative risk in the present study closely corresponds not only with the circadian rhythm of sleepiness/alertness but also with the other findings on the sleep-ascribed vehicle accidents (Garbarino et al., 2001: Home & Reyne, 2001). It is interpreted that sleepiness could be an important contributing factor in Korean highway vehicle accidents.