The effects of split sleep on sleepiness on performance: A train simulator study

Fatigue and sleepiness are critical safety risks in train operations, particularly among train drivers. One contributing factor is poor sleep quality, which may result from split or fragmented sleep patterns due to operational schedules and personal time-use constraints. This study aimed to investigate the effects of split sleep on fatigue and sleepiness during simulated train operations. Fifteen male participants completed a 2.5-hour train-driving simulation under three sleep conditions: split sleep (05:00 a.m. – 10:00 a.m. and 00:00p.m. – 3:00p.m.), consolidated daytime sleep (05:00 a.m. – 01:00p.m.), and baseline nighttime sleep (09:00p.m. – 05:00 a.m.). Sleepiness was assessed using ocular measures (blink duration, blink frequency, and microsleep per minute), subjective video rating, EEG parameters (alpha and theta wave power), and the Karolinska Sleepiness Scale (KSS). Results showed that the split sleep condition led to a substantial increase in fatigue indicators, with ocular and facial measures increasing by 15–70% compared to baseline. The consolidated sleep condition produced moderate increases (9–31%). No significant differences were observed in EEG parameters, and subjective KSS scores showed only marginal changes. These findings indicate that, despite an equivalent total sleep duration, split sleep patterns significantly impair alertness. The results highlight the need for careful scheduling and the provision of appropriate rest facilities in operational settings to mitigate fatigue-related risks.