Chris Watling, a sleep technician and masters student at Queensland University of Technology’s (QUT) Centre for Accident Research and Road Safety – Queensland (CARRS-Q), said the study also found that even when subjects said they felt alert after a rest break their response times did not demonstrate this.
Mr Watling gave 20 participants aged 20 to 25 years a simulated driving task to test their ability to detect and respond to potential hazards such as merging vehicles or vehicles that brake suddenly.
He said that during the simulated hazard-perception driving task participants had to click a button when they recognised a potential hazard while watching a video of driving on real roads. The simulated ‘trip’ included city and country driving.
“Hazard perception is a very important driving skill and it has been shown to be the only driving skill that has a consistent relationship with crashes,” he said.
“Our participants were slightly sleep-deprived before undertaking the driving task as many people in the community are.
“Instead of the recommended eight hours’ sleep, the participants had had six to seven hours’ sleep before the task.
“We attached electrodes to the participants to record their brain activity levels so that we could get an objective measure of sleepiness.
“Participants undertook a simulated-driving task for two hours; each participant then had either a 15-minute nap or a 15-minute rest break that included 10 minutes of brisk walking, followed by another hour of simulated driving.
“We tested each participant in the nap mode and the rest break mode on separate occasions.”
Mr Watling found that the nap group’s brain activity levels showed a decrease in sleepiness after the nap, which was to be expected, but the rest break group showed no decrease in sleepiness although they reported feeling more alert after the rest break.
“The rest break group showed a significant increase in the time it took to respond to potential hazards, an increase of more than half a second,” he said.
“This increase in reaction time corresponds to travelling approximately an extra 10 meters at 60 km/h and an extra 16m at 100 km/h. Whereas, those who napped had no change to their response time during that last hour of driving.
“Immediately after the rest break, the participants reported feeling less sleepy. This effect could give a false sense of safety as the objective brain activity levels showed no change in sleepiness levels.”
Mr Watling said the results from this study suggest that a rest break, even with light exercise, does nothing to improve hazard perception ability or for decreasing sleepiness levels but, a short nap has a restorative effect for drivers.
He also stressed that longer nap durations could lead to suffering from what is called sleep inertia, which is a short period of time of excessive sleepiness.
“Of course this is a safety concern itself, so it is important to wait until the sleep inertia has ended before driving again,” Mr Watling said.
“It would appear that if you are driving on a long trip, pull over every couple of hours or at the first sign of sleepiness and have a quick 15-minute kip. It could help you to survive your drive. “
Mr Watling described some of the signs of sleepiness to watch out for when driving, these include:
- Yawning or rubbing your eyes repeatedly
- Shifting in your chair frequently
- Daydreaming or wandering thoughts
- Increased blinking of the eyes but at a slower speed than normal
- Drifting within your lane
Media contact: Niki Widdowson, QUT media officer, 07 3138 1841 or firstname.lastname@example.org.