We understand a great deal about how and when alcohol will affect driving performance, and we have good technology available to evaluate drivers and to enforce drink-driving rules. Unfortunately, this is not the situation for fatigue.
There is no ready device to evaluate how tired and sleepy drivers are on our roads. As a result, our efforts to reduce driver fatigue have focussed mainly on telling drivers to note the symptoms of fatigue and to take breaks often, and at least every two hours.
The problem with this approach is that it has not been clear whether drivers are able to detect when they are too tired to drive. There is good evidence from many studies that people can drift into the early stages of sleep without actually being aware of it.
Being asleep at the wheel has obvious negative consequences for road safety and we need to avoid it at all costs. On the other hand, every driver knows the feeling of starting to feel tired and sleepy, and has experienced the discomfort of putting in more effort to stay focussed on the task of driving when tired.
To help direct our efforts to manage driver fatigue, we really need to know whether drivers have access to information about their current levels of fatigue and sleepiness sufficient to make a decision to do something about it.
A group of researchers from UNSW set out to try to answer this question. The project was a collaborative effort involving myself, Rena Friswell and Raphael Grzebieta, from Transport and Road Safety Research in the School of Aviation, and Jake Olivier, from the School of Mathematics and Statistics. It was funded by the NHMRC.
The aim of our study was to investigate the extent to which we have access to information about our current fatigue state and levels of drowsiness, and their implications for detection of changes in driving performance and the likelihood of crashes.
This research is significant because it will provide the much-needed evidence on which innovative fatigue policy can be developed for road safety, rather than the current make-do approach. That will show whether relying on subjective fatigue states will provide a valid estimate of safety-relevant driving performance effects or whether other indicators would be more useful.
The project involved studying the driving performance of 90 drivers in a two-hour drive in our driving simulator. They were asked to make ratings of their sleepiness and the likelihood of falling asleep and of crashing over the next few minutes. The participating drivers were encouraged to be tired during the drive: we asked them to have shorter than usual sleep on the night before the drive; we tested them in the afternoon, when fatigue is more likely; and we ensured that the drive was monotonous.
We found that almost all drivers experienced and could report increasing levels of sleepiness and likelihood of falling asleep, and of crashing, over the two hours of the drive. Most importantly, drivers who reported that they were possibly, likely or even very likely to fall asleep in the next few minutes, were over four times more likely to crash.
The research showed clearly that drivers can detect changes in their levels of fatigue and sleepiness that will clearly compromise their ability to drive safely. Clearly, if you are aware that you could even possibly fall asleep in the next few minutes while you are driving, you should stop driving.
Our results provide some new and clearer directions for road-safety policy. We need to do more than just ensure that drivers are aware of the signs of sleepiness when they are driving. We now know that they are aware of them. What is now needed is further efforts to encourage drivers to respond to these changes.
We need to educate drivers on the dangerous link between feeling sleepy and the strong likelihood that you could fall asleep and crash. We need to educate drivers on the best options for overcoming sleepiness when driving such as napping, avoiding at driving at all when tired, and the effective use of caffeine-containing drinks. We need to motivate drivers to do the right thing when they experience sleepiness while driving. This could include more frequent and more enticing places to pull over and stop. It could also include stronger and more emphatic penalties for drivers who choose to continue to drive and who crash due to fatigue.
This research is an excellent example of how good road-safety policy can benefit from research. Driver fatigue will continue to be a difficult problem but this research gives a more informed basis for directing action.
It shows that deciding to drive when sleepy or fatigued is a decision similar to deciding whether or not to drive after drinking: just as we encourage drivers to make safe decisions about when to drive in relation to alcohol and drugs, we need to encourage them to make safe decisions about fatigue.
Professor Ann Williamson is Professor of Aviation Safety in the UNSW School of Aviation and UNSW Transport and Road Safety.