Bus Drivers Working Hours and the Relationship to Driver Fatigue

Bus drivers often have irregular working hours like split shifts and their work involve high levels of stress. These factors can lead to severe sleepiness and dangerous driving. The purpose of this study is to highlight how split shifts affect sleepiness and performance during afternoon drive. The study is an experiment on real road with an equipped bus driven by professional bus drivers. The study design is a within subject design and the 18 professional bus drivers (9 males and 9 females) drove twice during afternoon; once after a day with bus driving in the morning and once after a day when they had been off duty the whole day. The hypotheses was that split shifts contribute to sleepiness during afternoon, which together can result in increased safety risks. The overall results support this hypotheses. In total five out of 18 drivers reached levels of severe sleepiness (Karolinska Sleepiness Scale ≥ 8) with an average increase in KSS of 1,94 driving in the afternoon the day that preceded with bus driving in the morning compared to the day off duty in the morning, an increase corresponding to the levels of shift workers comparing start and end of a night shift. The Psychomotor Vigilance Task showed significant increased Response Time with split shift (afternoon: 0.337s; split shift 0.347s), so did also the EEG based KDS mean/max. Blink duration also increased, even though the difference was not significant. One driver fell asleep during the drive. In addition, 12 of the 18 bus drivers reported that they in their daily work had to fight to stay awake while driving the bus at least 2-4 times per month. Even though the study showed significant induvial differences, it is clear that the bus drivers had to fight to stay awake and countermeasures are needed in order to guarantee safe driving under split shift schedules.