Sleepy driving is a serious problem that can lead to car crashes. Sleepiness causes motor vehicle accidents because it impairs concentration and can lead to the driver falling asleep at the wheel.
Important aspects of driving impairment associated with sleepiness are reaction time, vigilance, attention, and information processing. The exact prevalence is not known in Singapore.
Sleepiness-related crashes is an under-recognised problem and may be categorised as fatigue and inattention.
Although society today gives sleep less priority than other activities, sleepiness and performance impairment are responses of the human brain to sleep loss/ deprivation. There is currently nothing that can reduce the human need for sleep. Microsleeps, or involuntary intrusions of sleep or near-sleep, can overcome even the best intentions to remain awake.
A typical crash related to sleepiness has the following characteristics:
- It occurs during late night/early morning, or mid-afternoon
- The crash is likely to be serious
- A single vehicle leaves the roadway
- The driver does not attempt to avoid a crash
- The driver is usually alone in the vehicle
Risks for Sleepy Driving Crashes
• Sleep loss
The need for sleep varies among
people - sleeping eight hours per
24-hour period is common, and
seven to nine hours is needed to
optimise performance. Sleeping
less than 4 consolidated hours
per night impairs performance on
vigilance tasks. Acute sleep loss,
even the loss of one night of sleep,
results in extreme sleepiness.
The effects of sleep loss are
cumulative. Regularly losing one
to two hours of sleep a night can
create a ’sleep debt’ and lead to
chronic sleepiness over time.
Only sleep can reduce sleep debt.
Sleep loss can be work-related or a
• Sleep quality
The quality of sleep is also
important. Sleep disruption and
fragmentation lead to inadequate
sleep and can negatively affect
functioning. Sleep fragmentation
can be caused by illness, including
untreated sleep disorders.
Disturbances such as noise, young
babies, children, activity and lights,
a restless/snoring spouse, or jobrelated
duties (e.g. workers who are
on call) can interrupt and reduce
the quality and quantity of sleep.
• Driving patterns: Late-night driving between midnight and 6 am, driving in the mid-afternoon hours and driving for longer periods without taking a break.
• Use of sedating medications, especially prescribed anxiolytic hypnotics, tricyclic antidepressants, and some antihistamines.
• Untreated or unrecognised sleep disorders, especially sleep-related breathing disorders, obstructive sleep apnoea syndrome and narcolepsy.
• Consumption of alcohol, which interacts with and adds to drowsiness.
A combination of these factors increases crash risk substantially.
Why Sleepy Driving Accidents Happen
Sleepiness leads to accidents because it impairs human performances that are critical to safe driving.
People can use physical activity and dietary stimulants to cope with sleep loss and mask their level of sleepiness. However, when they sit still to perform repetitive tasks like driving, sleep comes quickly.
Sleepiness leads to:
- Slower reaction time: At high speeds, delay in reaction time can have a profound effect on crash risk.
- Reduced vigilance
- It takes longer for information on the roads to be integrated and processed.
People at Highest Risk
- Young people (ages 16 to 29), especially males
- Shift workers whose sleep is
disrupted by working at night or
working long or irregular hours
- People with untreated Sleep
Apnoea Syndrome (SAS) and
Assessment for Chronic Sleepiness
The Epworth Sleepiness Scale (ESS)
is an eight-item, self-report measure
that quantifies individuals’ sleepiness
by their tendency to fall asleep ’in
your usual way of life in recent times’
in situations like sitting and reading,
watching TV, and sitting in a car that
is stopped for traffic.
People with a score between 10 to14
are considered moderately sleepy,
whereas a score of 15 or greater
indicates severe sleepiness.
To prevent sleepy driving and its consequences, you need to know the benefits of behaviours that help you avoid becoming sleepy while driving.
- Getting sufficient sleep and taking a short nap (15 to 20 minutes) when sleepy
- Not drinking alcohol when sleepy
- Limiting driving between midnight and 6 am
- Taking caffeinated drinks/food e.g. coffee
- Detection and treatment of illnesses that can cause excessive sleepiness like sleeprelated breathing disorders obstructive sleep apnoea syndrome and narcolepsy