Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 263171
Loughborough University

School of Sport, Exercise and Health Sciences


Falling asleep at the wheel

Why do drivers fall asleep at the wheel? 

Falling asleep is always preceded by a period of increasing sleepiness, which drivers are quite aware of, to the extent that will do things to keep themselves awake (opening window, turning up the radio, stretching etc), but continue to drive rather than 'take a break'. Why do they fail to heed these warnings, believing they won't actually fall asleep and are 'safe' to drive? Young men are the most likely persons to do this, even when they are struggling to stay awake.

Driving and Obstructive Sleep Apnoea 

Very heavy snoring alternating with 'gagging' sounds, and a heaving chest are the usual signs of this disorder, which causes much disruption of sleep and, as a result, excessive daytime sleepiness. Sufferers can remain like this for many years until treated. The disorder is usually treatable, but requires referral to a sleep disorders clinic. Using our 'state of the art driving simulator', we are looking at the ability to 'drive alert' in those people who have been successfully treated.

Low Blood Alcohol Levels, Well Under the Legal Driving Limit, Worsen Sleepiness 

Just one lunchtime drink, giving a blood alcohol level that would easily pass the breathalyser test could still be dangerous for drivers, because of alcohol's impact on the natural afternoon dip in mental alertness. This combined effect of sleepiness and moderate alcohol intake is even worse for drivers who have not slept well the night before. We are looking at driving in the small hours of the morning (when one would normally be asleep), after having had only a few drinks that evening but are well under the legal limit.


Sleepy drivers should stop driving and take a 30 minute break at a safe place. We have shown (now recommended in the Highway Code) that a caffeinated drink immediately followed by a short nap before the caffeine kicks in, make an ideal combination for combating moderate sleepiness. Despite advertising claims, some caffeine products are much better and others in this respect, and drinks with a very high sugar content can worsen sleepiness. We are assessing these products and claims.