• Experiment demonstrates reaction times are significantly slower and the risk of falling asleep at the wheel significantly increases with lack of sleep even in the short term
  • Driving after suffering from disrupted sleep can be as dangerous as driving after no sleep
  • Further research reveals 83 percent of UK drivers have driven tired
  • 28 percent of passengers of tired drivers have felt scared for their safety

An experiment that took place at the UK’s Transport Research Laboratory (TRL) with a set of triplets has revealed how dangerous it is to drive whilst tired.

The triplets
To ensure the experiment was as fair as possible, a set of male triplets, aged 27, was sourced; Robert Davis, Steven Davis and Patrick Davis.

The night before
The experiment involved the triplets having differing levels of sleep. After picking straws, Robert chose the longest, which meant he had the luxury of a full night’s (normal) sleep, whereas Steven picked the mid-length straw, meaning he had a night of disrupted sleep thanks to a lifelike robotic baby. This was to mimic the sleeping patterns of a parent with a young child. Finally, Patrick selected the shortest straw meaning he was awake all night, to demonstrate the full effect of sleep deprivation on driving and to highlight the dangers of those that work at night and then drive home the next day.

The driving test
The next day the triplets each drove the same driving simulator at TRL, a provider of independent and impartial research, consultancy, testing and certification for all aspects of transport. This was a 90-minute drive in a real car surrounded by projections of a motorway, ensuring the experience was as true to real life as possible.

Each drove whilst wearing a heart rate monitor which gave alerts when the triplets’ heart rate dropped to a level classified as fatigued observed by principal psychologist, Simon Tong from the control room next door. Each triplet was asked to stick to the inside lane of the three-lane motorway and drive at a constant speed of 60mph. Every five minutes they were asked to rate their own level of sleepiness, with 1 being ‘very alert’ and 9 being ‘very sleepy’.

Throughout the drive they were also asked to flash their headlights whenever a red bar appeared above the motorway, for the scientists to monitor their reaction times. The driving simulator recorded driver and vehicle movements throughout each drive so that there was a detailed record of speed, acceleration and lane keeping.

Robert, who had a full night’s sleep had no fatigue alerts from the heart rate monitor, had the fewest lane departures (30 departures and a total of 39 seconds out of his lane). Steven had four fatigue alerts and left his lane a total of 58 times for a duration of 1 minute and 40 seconds. Patrick not only received 12 fatigue alerts but his ability to stay in the same lane was severely reduced, with 188 separate lane departures, equivalent to 6 minutes and 26 seconds travelling out of his lane.

Interestingly it was Steven, with disrupted sleep, who had the slowest reaction times, which highlights that even people who have managed to have some sleep are still putting themselves and others at risk by driving. He failed to react ten times, which was twice as often as Patrick and substantially more than Robert who had no missed reactions.

The research was commissioned and funded by Time4Sleep.co.uk, who also commissioned a survey of 1000 UK drivers to support the experiment. The data discovered that over three quarters of drivers (83 percent) have driven tired with 1 in 10 confessing to do it regularly.

A third of people (33 percent) admitted to feeling like they had put people at risk in the past whilst driving tired with 23 percent saying they didn’t feel in control and 19 percent saying they felt they would fall asleep at the wheel. A further 19 percent said they felt they had been in danger of causing a collision and a quarter (25 percent) revealed they felt their reactions were slower and they shouldn’t be driving.

55 percent of respondents also said they had been a passenger of a tired driver in the past. 28 percent of those said they had been scared for their safety and a further 20 percent felt they were going to crash. Worryingly 19 percent also said they didn’t feel comfortable asking the driver to stop.

Simon Tong, principal psychologist at TRL, said: “The findings of our experiment reveal just how important it is to only undertake driving when feeling alert and having had sufficient sleep. The key finding here was how affected Steven was with disrupted sleep as this is most common to real life.”

“One dangerous aspect of fatigue is how it can come and go quite suddenly.”

“You can get a false impression that you’ve overcome it, only to find that it strikes again a short time later when you perhaps aren’t expecting it. This was clearly seen when we observed Steven doing his drive.”

“Robert’s drive was near perfect, which is to be expected of someone who has had 7-8 hours sleep as Robert did the night before. However, Patrick was driving on a different level, with terribly slow responses, imprecise motor skills and a self-confessed lack of control. He was unable to stick to a lane or speed and his driving performance was akin to being drunk, if not worse.”

For more information on how the experiment took place, please visit the information hub at www.time4sleep.co.uk/dont-drive-tired