Fatigue
Fatigue
What fatigue is
Fatigue is a physiological condition that can occur long before you fall asleep at the wheel. It has a negative impact on your reaction time, your ability to concentrate and your general understanding of the road and traffic around you. There are 3 main causes of fatigue.
Sleep loss — this is the most commonly known cause of fatigue. Different individuals require different levels of sleep, although the average is 7 to 8 hours of sleep a day. If you do not get a full night’s sleep, it is likely to cause fatigue and this can build up over time if your sleep continues to be restricted.
Circadian rhythms — everybody has a built-in body clock in their brain that biologically determines when they will feel sleepy. These circadian rhythms programme us to feel at our most sleepy between 3am and 5am, and between 3pm and 5pm.
Time spent driving/working — research shows that the longer people spend driving without a break, the greater their level of fatigue. Also, the time spent in other activities such as work, school, and so on, can increase fatigue and affect subsequent driving.
Research shows that fatigue is difficult to identify and recognise as having a role in a crash (Williamson and Chamberlain, 2005), so the contribution of fatigue to crashes may be under-represented in the police-reported crash system that has been used for this factsheet.
Summary for 2023
In 2023, there were 25 fatal crashes, 59 serious injury crashes, and 455 minor injury crashes where driver fatigue was a contributing factor.
In these crashes, 30 people died, 80 people were seriously injured, and 576 people suffered minor injuries.
Deaths in crashes involving driver fatigue since 1984
Casualties in crashes involving driver fatigue as a contributing factor
Crashes involving driver fatigue as a contributing factor
Contribution of driver fatigues to crashes
Over the years 2021 - 2023, driver fatigue was a factor in 9 percent of fatal crashes, 3 percent of serious injury crashes, and 5 percent of minor injury crashes.
Percentage of crashes with driver fatigue as a contributing factor (2021 - 2023)
Alcohol/drugs, speed and fatigue in fatal crashes (2021 - 2023)
Alcohol/drugs and/or speed were also contributing factors in 61 percent of fatal crashes that involved driver fatigue.
The faster people drive, the less time they have to react (Patterson, Frith and Small, 2000); this becomes even more dangerous when combined with the slow reactions already caused by fatigue. Similarly, even small amounts of alcohol/drugs can combine with fatigue to give a high crash risk (Phillip et al, 2001).
Driver fatigue in fatal crashes by road type (2021 - 2023)
Between 2021 and 2023, 86 percent of the fatal crashes that involved fatigue as a contributing factor occurred on the open road. The remaining 14 percent occurred in urban areas.
Who dies in crashes involving fatigue
For every 100 drivers or riders who died in road crashes where their fatigue was a contributing factor, 35 of their passengers and 37 other road users died with them.
Who dies in crashes in which fatigue is a contributing factor (2021 - 2023)
| Age | Fatigue involved driver' | Passengers with fatigue involved drivers | Other road users | Percent of all deaths in crashes by age group |
|---|---|---|---|---|
| 0 | 0 | 0 | 0% | |
| 0-14 | 0 | 3 | 2 | 17% |
| 15-19 | 4 | 3 | 0 | 7% |
| 20-24 | 11 | 3 | 1 | 12% |
| 25-29 | 6 | 2 | 2 | 10% |
| 30-34 | 7 | 2 | 1 | 9% |
| 35-39 | 6 | 1 | 1 | 11% |
| 40-44 | 0 | 0 | 2 | 4% |
| 45-49 | 3 | 1 | 2 | 12% |
| 50-54 | 3 | 3 | 1 | 10% |
| 55-59 | 4 | 2 | 1 | 11% |
| 60+ | 16 | 1 | 9 | 10% |
| Total | 60 | 21 | 22 | 10% |
Drivers affected by fatigue
Drivers involved in fatal crashes by vehicles type (2021 - 2023)
From 2021 - 2023, driver fatigue a contributing factor in fatal crashes for 7.3 percent of car and van drivers, 1.8 percent of motorcyclists, and 1.6 percent of truck drivers.
Drivers affected by fatigue in fatal or serious injury crashes by age group (annual average, 2021 - 2023)
License status of fatigued drivers in fatal crashes (2021 - 2023)
Note: Unknown/other includes drivers with an expired, unknown or incorrect licence class. Disqualified includes drivers who have been forbidden to drive.
Types of crashes with fatigue
Types of fatal crash where driver fatigue was a factor (annual average (2021 - 2023))
Fatal and injury crashes with driver fatigue as a contributing factor by time of day (annual average (2021 - 2023))
Between 3 am and 5 am our body clocks (circadian rhythms) program us to feel sleepy. There is also a secondary peak in sleepiness between 3 pm and 5 pm. This is the time of day when physical and mental performance is at its worst. There are broad peaks in fatigue related fatal and injury crashes in the early morning and through the afternoon.
Note:
For further information on the causes of fatigue and how to prevent them, see
References
Patterson, T.L., Frith, W.J., and Small, M.W. (2000) Down with Speed: A review of the literature, and the impact of speed on New Zealanders Accident Compensation Corporation and Land Transport Safety Authority. Wellington. https://transport.govt.nz/assets/Uploads/Report/ACC672-Down-with-speed.pdf [PDF, 1.1 MB]
Phillip, P., Vervialle, F., Le Breton, P., Taillard, J., Horne, J. A. (2001) Fatigue, alcohol, and serious road crashes in France: factorial study data. British Medical Journal. 322 p 829-830
Williamson, A., & Chamberlain, T. (2005). Review of on-road driver fatigue monitoring devices.
Based on data extracted from the Crash Analysis System 2024-09-18.