Dangers of driving after night shifts

Authors: Ian Morrison, Renata L Riha, Neil Douglas, James A Horne 

Publication date:  05 May 2012

Ian Morrison and colleagues revisit the evidence and dangers of driving after a night shift

A recent debate in the Scottish Parliament[1] has again raised the issue of the safety of hospital workers when driving home after a night shift, a matter that was highlighted five years ago by the Royal College of Physicians in a survey of junior hospital doctors.[2]

Hospital working patterns in the United Kingdom have changed with the introduction of the European Working Time Directive. Overnight cover can last around 12 hours, and medical staff are expected to work throughout the night. Although breaks are possible, the minimum requirement is only 20 minutes if the shift exceeds six hours. Many hospitals now expect their medical staff to stay awake throughout the night and have withdrawn on-call bedrooms, a move opposed by the BMA and the Academy of Royal Colleges.[3]

Doctors who have been awake for more than 20 hours, which may occur at the end of their first night shift, often experience increased sleepiness compounded by their daily circadian (body clock) trough. The combined effect leads to performance impairment similar to that resulting from a blood alcohol concentration of 100 mg/100 ml,[4] well over the UK driving limit.

The effects of this reduced performance on the care of patients has been a focus of concern,[5] but doctors may also suffer. Those on night shifts are up to three times more likely to be involved in a road traffic incident than those working other shifts.[6] [7] The situation is aggravated by longer commutes by doctors required to rotate through several hospitals during their specialty training.

Although adaptation to night shifts is possible with time, for junior medical staff such shifts occur in relatively short blocks in an attempt to maximise training opportunities during the day. These blocks are often too short for adequate adaptation, even with judicious use of light[8] and other countermeasures. Of further concern is the finding that young drivers are more affected by sleep loss than are older drivers.[9] Apart from greater sleepiness, sleep loss also tends to subtly elevate mood among younger drivers, as well as impairing decision making, which together can result in drivers feeling overly optimistic about being able to drive safely.[10]

Although short naps (<20 minutes) during the night can help maintain alertness on duty,[11] there is no evidence that these could reduce end of shift sleepiness during monotonous driving. A 200 mg dose of caffeine (two or three cups of coffee) taken 30 minutes before driving might work for around 30 minutes.[12] However, self medicating with relatively high doses of caffeine in this manner implies awareness of being unsafe to drive, and in the United Kingdom drivers have a legal duty to ensure that they are fit to drive.

Many recent medical graduates experiencing night shifts for the first time will be unaware of the risks of sleep deprivation. It is important that they recognise these and accept that working a night shift, particularly on the first night, requires adequate preparation. Likewise, those who set the rotas should do so in accordance with best evidence to ensure the safety of their employees, even if this affects training.

Any doctors who are excessively sleepy at the end of a night shift should acknowledge the dangers and not drive. Provision must be made to get them home safely, especially if and when such work hours are wholly and necessarily part of their duties.

Competing interests: None declared.


  1. Alex Salmond under fire over hours worked by junior doctors. Daily Record  2011, Nov 13.
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  3. BMA Junior Doctors Committee and Academy of Medical Royal Colleges’ Trainees’ Committee. Joint position statement on on-call rooms, June 2006.
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  9. Lowden A, Anund A, Kecklund G, Peters B, Akerstedt T. Wakefulness in young and elderly subjects driving at night in a car simulator. Accid Anal Prev  2009;41:1001-7.
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  11. Folkard S, Tucker P. Shift work, safety and productivity. Occup Med  2003;53:95-101.
  12. Reyner LA, Horne JA. Early morning driver sleepiness: effectiveness of 200 mg caffeine. Psychophysiology  2000;37:251-6.

Ian Morrison consultant neurologist   Department of Neurology, Ninewells Hospital, Dundee, UK
Renata L Riha consultant sleep physician  Department of Sleep Medicine, Royal Infirmary of Edinburgh, Edinburgh, UK
Neil Douglas professor of respiratory and sleep medicine  Department of Sleep Medicine, Royal Infirmary of Edinburgh, Edinburgh, UK
James A Horne professor of psychophysiology  Sleep Research Centre, Loughborough University, Leicestershire, UK


Cite this as BMJ Careers ; doi: