ATSB – RO-2018-004
had no high-risk factors, such as a body mass index greater than 40, which would trigger a referral for a sleep study.
Sydney Trains, like other Australian rail operators, is not required to automatically send all employees in safety-sensitive positions for a sleep study. The National Health Standards for Health Assessment of Rail Safety Workers specifies certain criteria for sleep study referral and the driver of A42 did not meet these criteria.[1]
Another factor that increased the likelihood of a microsleep was that the driver had been awake since 0215, more than 7 ½ hours prior to the time of the incident. It has been reported that both feelings of fatigue and the occurrence of microsleeps increase as duty time progress.[2] The National Transport Commission recognises that the duration of a duty period is a contributor to fatigue-impaired work performance.[3] Early morning shifts are associated with high levels of fatigue and this can affect performance for the duration of the shift.[4] Also, some research has shown that shifts ending around the time of this accident show an increase in mental tiredness for train drivers. [5]
The driver was rostered to have 3 days off (Friday, Saturday and Sunday) before the incident day, Monday. Instead, he was phoned on Friday by the roster clerk and asked to work an overtime shift the next day, Saturday. He said he worked from 1500 to 2300 on Saturday and went to bed at 0200 in the early hours of Sunday morning. He awoke at 0830, having slept approximately 6 ½ hours. The driver said he was used to early morning shifts and he would rather have not worked the afternoon/evening shift on Saturday. This change in shift meant that he changed his sleeping pattern from going to bed in the late evening (2130-2200) for the previous 5 days, to going to bed in the early hours of Sunday morning.
On Sunday, instead of resting at home and taking the opportunity for an afternoon nap, the driver went shopping with his family from approximately 1300-1630. Originally, the driver thought that he had napped that afternoon but an analysis of mobile phone records showed otherwise. The driver went to sleep Sunday evening at 2000 and set an alarm for 0215. The driver had the opportunity for approximately 6 hours sleep the night before the accident, and 6 ½ hours sleep in the previous 24-hour period. Research has shown that limiting sleep to six hours or less over successive nights can result in a deficit in performance[6] and that sleep of only six continuous hours is associated with an elevated likelihood of a fatigue related incident.[7] It is suggested that the average amount of sleep required per 24-hour period for most people is approximately 8 hours.
There were two opportunities for the driver to increase his sleep hours. Firstly, after he completed his Saturday shift at 2300 when he did not go to bed until 0200. It is accepted that often people need a period of time to wind down after work before going to bed, but the 3 hours taken this evening may have been detrimental. Secondly, during the day on Sunday, he did not take the
- ↑ The NTSB, in their 2019 Most Wanted List, has targeted reducing fatigue-related accidents as a priority. It is noted that the Board has recommended the Federal Railroad Administration to require rail operators to screen employees in safety-sensitive positions for sleep apnea or other sleep disorders. National Transportation Safety Board. Most Wanted List of transport safety improvements 2019-2020. www.ntsb.gov/mostwanted
- ↑ UK Rail Safety and Standards Board (2004). Human Factors study of fatigue and shift work. Appendix 1: Working patterns of train drivers implications for fatigue and safety. p.66.
- ↑ National Transport Commission (2008). National Rail Safety Guideline. Management of Fatigue in Rail Safety Workers. p.5.
- ↑ Folkard S, Robertson KA, Spenser MB (2006). The development of a fatigue / risk index for shiftworkers. p.17
- ↑ UK Rail Safety and Standards Board (2004). Human Factors study of fatigue and shift work. Appendix 1: Working patterns of train drivers implications for fatigue and safety. p.65.
- ↑ Folkard S, Robertson KA, Spenser MB (2006). The development of a fatigue / risk index for shiftworkers. p.12.
- ↑ Stutts JC, Wilkins JW, Osberg JS, Vaughn. Driver Risk Factors for Sleep-related Crashes, Accident Analysis and Prevention, 2003.
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