Road safety linked to driver fatigue
Mar 06 2014
The South Australian transport department (SATD) mentions fatigue as a major factor in causing road crashes, although its contribution to individual cases is hard to measure and is often not reported as a cause of crash. Driver fatigue is particularly dangerous because one of the symptoms is decreased ability to judge our own level of tiredness. SATD believes that fatigue is more likely to be a factor in crashes in rural areas as they can involve long trips and extensive periods of continuous driving; however, the fact is that anyone can be affected by fatigue.
If you don’t get enough sleep, you go into sleep debt and you owe yourself more sleep. The only way to repay this debt is by sleeping. Until you catch up on your sleep, you will have a greater risk of having a fatigue-related crash. SATD says that not sleeping for more than 17 hours has an effect on driving ability the same as a blood alcohol concentration (BAC) of 0.05. Not sleeping for 24 hours has the same effect of having a BAC of 0.10, double the legal limit. Thus, the accumulation of fatigue is a non-linear process.
To quote prominent sleep physician, William Dement: “Drowsiness is the last step before falling asleep, not the first”. Drowsiness means you are seconds away from falling asleep. Dement goes on to explain that: “The crucial event that occurs as we fall asleep is an abrupt shut down of the neural processes that allow us to perceive the world around us. At one moment we are awake, and can see and hear. A fraction of a second later, we are asleep, and we are completely blind and completely deaf.” In fact, many sleep experts think of sleep as the “default programme”, the state that exists when we are no longer working to maintain wakefulness. When we can no longer resist sleep, when our alerting centres can no longer prevent sleep, we transition to sleep.
Fatigue might lead to loss of vehicle control. The good part is that there are several warning signs of fatigue. The bad part is that we often don’t understand them or worse yet, choose to ignore them. Some of the warning signs include: feeling sleepy or tired, being unaware of your environment or not always knowing where you are, erratic driving similar to drunk driving, unable to get comfortable, tired or burning eyes, rubbing your neck or face to wake up, and driving off the shoulder or crossing the centre line.
It is also interesting to see how fatigue might interact with other factors in the environment. According to New Zealand’s transport department (NZTD), driver fatigue often combines with other factors, such as alcohol and speed, to cause road crashes. The first interaction with alcohol is dangerous. For example, of the 134 fatal crashes in which driver fatigue was a factor between 2002 and 2004, 39 also involved driver alcohol. As per NZTD, these figures are likely to be on the conservative side, because alcohol can affect a driver’s alertness long before the legal limit is reached. Any amount of alcohol can combine with fatigue to affect your driving.
As per NZTD, speed and fatigue are also a bad combination. The faster you drive, the less time you have to react to the unexpected. When you’re tired, fatigue slows your reactions. Speed was a contributor to 12 of the 134 fatigue-related fatal crashes between 2002 and 2004, says NZTD. As with alcohol, it’s possible that speed makes up a larger proportion of fatigue-related crashes than we can identify. Speed often goes unreported in crashes because drivers don’t often admit they were speeding, especially if they’ve admitted they were tired.
So, the question is how can we reduce fatigue or improve our alertness? The first advice that is given by most transport departments is to get plenty of sleep before a long journey. It is advisable to plan to drive during times of the day when you’re normally awake, and stay overnight rather than travelling straight through. Thus, one should avoid driving during times when we’re programmed to be sleepy.
The second advice is to schedule a break at least once every two hours, and whenever you begin to feel sleepy. During a break, get out of your vehicle and have a walk, or some form of exercise, to increase alertness. If you realise you need a nap, don’t wait. Find the first safe place and pull over. Try to avoid napping in the driver’s seat, and try not to nap for longer than 40 minutes. Naps up to 40 minutes can be very refreshing, but naps longer than 40 minutes can leave you feeling groggy and disoriented for up to 10 to 15 minutes after you wake up. (This is called sleep inertia.)
Lastly, eat sensibly throughout the journey, but avoid large meals. In addition, caffeine drinks (tea, coffee and cola drinks) help you stay alert, but they take time to be effective. Research has shown that drinking a caffeinated drink, followed by a 20-minute nap, improves alertness in the short term. And if you have a driver on the next seat, please share your driving.
(The writer is on the faculty of Indian Institute of Technology, Mandi, India)