Fatigue in road traffic
Fatigue has different causes. A distinction is often made between sleep-related fatigue and task-related fatigue. Given the many causes, almost everyone is tired sometimes. Consequently, fatigued driving is fairly common. For example, in a large-scale international survey between 20 and 25% of the car drivers indicated that, during the last month, they had driven at least once while they were so sleepy that they had trouble keeping their eyes open. Fatigued driving is relatively common among (international) truck drivers, people working in (night) shifts, young men, people with untreated sleep problems/disorders. Taxi drivers are also seen as a specific risk group for fatigued driving.
People who are tired tend to be less attentive and react less quickly and less adequately (e.g., more steering movements, more variation in speed and headway distance). Fatigue also affects mood and thus behaviour: tired people tend to get irritated and frustrated more easily. It is estimated that driver fatigue is a contributing factor in 15 to 20% of serious crashes, though the results of individual studies vary widely. Shares are higher for crashes involving trucks, for fatal crashes and for motorway crashes. When driving while fatigued, the risk of a crash increases considerably. A meta-analysis of 14 studies showed an increase in crash risk of 29% for fatigued drivers compared to those who were not fatigued.
Countermeasures
Almost all drivers acknowledge the dangers of driving while fatigued. Most drivers also recognise the signs of fatigue, but often this does not effectively prevent them from driving. They do tend to take actions to counteract fatigue, but these are generally less effective actions such as opening a window or talking to a passenger. More effective responses include taking a nap or asking a passenger to drive, but these are much less common.
Since it is difficult to quantify fatigue objectively, it is not possible to set and enforce legal limits for fatigued driving. For truck and bus drivers, driving time and rest period regulations can help prevent fatigue, provided that companies and drivers comply with these rules. Company fatigue management programmes emphasise the employer’s key role in setting fatigue-proof working conditions and informing employees. For non-professional drivers, education and information campaigns can help raising awareness of the problem of fatigue, but behavioural effects are likely to be limited.
In terms of infrastructure, the provision of sufficient locations and facilities allowing truck and car drivers to take a rest can help to prevent fatigued driving. Other infrastructure countermeasures can help to mitigate the consequences of fatigued driving, e.g., rumble strips to prevent running off the road. New vehicle technologies are promising, but the overall effects are still unknown. Automatic fatigue detection systems aim to warn drivers when they get tired. Advanced driving assistance systems (ADAS), e.g., lane keeping systems and forward collision warnings, aim to prevent the consequences of fatigued driving such as running off the road or colliding with a vehicle in front. The new EU Regulation on type approval requirements for motor vehicles makes a driver drowsiness and attention warning system mandatory for all vehicle categories.
