Role of Drowsy Driving in Traffic Accidents: A Questionnaire Survey of Thai Commercial Bus/Truck Drivers
Manoon Leechawengwongs MD*, Evelyn Leechawengwongs MD**, Chakrit Sukying MD*, Umaporn Udomsubpayakul MS***
Affiliation : * Vichaiyut Hospital, ** Samutprakarn Hospital *** Research Unit, Faculty of Medicine, Ramathibodi Hospital, Mahidol University
Objective : The authors assessed the relationship between traffic accidents and drowsiness.
Materials and Methods : A self-answered questionnaire survey of 4331 commercial bus/truck drivers was done.
Result: Sixty-nine percent of the drivers reported accidents and one third of these accidents was attributable
to drowsiness. Drowsy driving and microsleeps were experienced by 75% and 28% of drivers respectively.
Forty-five percent of drivers had excessive daytime sleepiness based on the Epworth Sleepiness Scale (ESS
score > 11). This excessive daytime sleepiness was strongly associated with feeling drowsy, microsleeps, and
accidents. The major causes of drowsiness were sleep deprivation (90%), medications that caused sleepiness
(78%), drinking alcohol the previous night (23%), and chronic loud snoring with or without obesity (17%).
61% of drivers worked longer than 12 hours with no days off. The feeling of drowsiness at the wheel was also
closely related to long hours of driving (> 4 hours). Countermeasures that drivers used to keep them awake
were talking to someone, drinking coffee or caffeinated-energy drinks, chewing snacks or gum and pulling
over to have a nap.
Conclusion : There is a strong relationship between accidents and drowsiness in commercial bus/truck driv-
ers. The main cause of drowsiness was sleep deprivation. The authors hope that this information will help the
public authority develop a policy to reduce the traffic accidents attributable to drowsy driving in commercial
bus/truck drivers.
Keywords : Drowsy driving, Traffic accidents, Bus/truck drivers
