What if you get a fine or lose your driver’s license because you’re tired? Our new study just published in Nature and Science of Sleep has found that if you slept less than five hours last night, you are just as likely to be in a car accident as if you were over the legal limit for alcohol.
We know about 20% of all vehicle accidents are caused by fatigue. Over the past 20 years, the number of accidents caused by alcohol has increased has dropped significantly.
However, little progress has been made in reducing fatigue-related accidents over the same period. We wanted to know: Can this be changed?
A ‘line in the sand’ about bad driving
The recent decrease in alcohol-related car accidents has happened for a number of reasons:
- a significant investment in public education
- drivers have easy-to-follow guidelines for deciding if they are too drunk to drive (eg the advice to have “two drinks in the first hour, then one drink every hour after that”)
- strong enforcement strategies, including roadside testing
- highly publicized drunk driving lawsuits.
In addition, drivers are legally deemed to be impaired if their blood alcohol concentration exceeds 0.05%, regardless of their driving ability. This blood alcohol limit is an effective “line in the sand” for determining if someone is legal allowed to drive.
We conducted a study to find out if we could reduce the number of fatigue-related accidents on Australian roads by following a similar strategy. Is there a time when we can consider a driver disabled due to fatigue?
A minimal amount of shuteye?
To do this, we evaluated the scientific evidence from lab and field studies that looked at how much prior sleep you need to drive safely.
After summarizing the findings of 61 unique studies, we found that getting less than four to five hours of sleep in the past 24 hours is associated with an estimated doubling of the risk of a car accident. This is the same risk of an accident as drivers with a blood alcohol concentration of 0.05%.
Not only this, but a driver’s risk of an accident increases significantly with every hour of sleep lost the night before. In fact, some studies suggested that if a driver had slept between zero and four hours the previous night, he could sleep up to 15 times. more chance of a crash.
Our research suggests that, based on scientific evidence, it may be reasonable to require drivers to have a certain amount of sleep before getting behind the wheel. If we were to tune in to the degree of risk considered acceptable for drunkenness, we might consider requiring a minimum of four to five hours of sleep before driving.
However, we need to consider more than just the scientific evidence. For the most part, drinking alcohol is something people choose to do. Many people can’t decide to sleep more – for example new parents, shift workers And people with sleep disorders. Not only that, but to regulate fatigued driving would require significant public support.
Read more: When is it time to stop driving? Will mandatory assessments of older drivers make our roads safer?
Is the law even an option?
We also need to think about how such a law will be implemented. There’s currently no way to evaluate roadside fatigue — no breath test or blood test that can assess how much sleep you’ve had or how bad you are. As a result, regulating fatigue should probably happen in the event of a crash. Was the driver at a disadvantage due to fatigue at the time and is he therefore legally responsible?
Regulating fatigued driving is not a new idea. In New Jersey, “Maggie’s Law” legislation states that drivers are legally disabled if they have had zero hours of sleep in the previous 24 hours. This law, introduced in 2003 after a tired driver killed a student, would be considered by many to be quite tolerant. That is, many people would expect you to need more than zero hours of sleep in the past 24 hours to drive safely. However, in Australia in 2023 there is no similar requirement to ensure you are well equipped to get behind the wheel.
We are currently consulting with a range of community members and road safety stakeholders about what the next step could be to regulate fatigued driving in Australia. Preliminary findings indicate that at least more specific public education and guidance for drivers on how to avoid driving while fatigued would be welcome. For example, easy-to-follow advice on how to decide whether or not you’re too tired to drive is likely to be well received.
While it may take some time in Australia to legislate on how much sleep you should get before you get behind the wheel, we recommend taking into account how much sleep you’ve had in the last 24 hours. If you’ve slept less than five hours, you probably shouldn’t be driving.
Read more: Why tailgate people? A psychology expert explains what’s behind this common (and annoying) driving habit