How fatigue, drowsiness and sleep affect driving

Although pointing out the cause of a traffic accident fatigue or sleep is somewhat complicated (unless those involved recognize it), insurance companies and experts agree in pointing out as two of the main causes of traffic accidents in Spain.

In 2015, the CEA Foundation made a report on the influence of these two symptoms on traffic accidents. Today we are going to analyze this report.

Physiological factors that affect driving: differences between fatigue, drowsiness and sleep

As for those physiological factors that people “can” control and which will directly affect our driving skills and reaction to the wheel, the most important are fatigue, drowsiness and sleep . And there are differences between the three, despite being related to each other and being precursors of others and in turn consequences of them.


As the pure definition of the word says, fatigue is ” the fatigue that is experienced after an intense and continuous physical or mental effort “. In this case, driving involves a continued mental effort to maintain 100% attention, since any minimal distraction can have fatal consequences. It is one of the most dangerous physiological states and is directly and dangerously related to sleep . As for physical fatigue, there is a question that many people ask themselves: does a manual change car or an automatic change car cause more fatigue? .

As a result of a long trip in which we do not make the appropriate stops (however much we think we are not fatigued), people tend to relax and stop paying attention even if we do not realize, thus lowering the guard during our driving .

Continuous movements and changes of posture , as well as constant blinking, heaviness of head, headaches, rubbing the face, stretching, etc. are clear symptoms that we are suffering, or beginning to suffer the onset of fatigue and, therefore, , we must stop as soon as possible .

According to the European Transport Safety Council (ETSC), driving fatigue causes almost 20% of the accidents of commercial transport vehicles in the European Union. Luckily, technology advances every time and brands like Toyota already have some devices and systems that prevent or help reduce the effects and consequences of fatigue behind the wheel .

The somnolence

Sleepiness is the ” intermediate state between sleep and wakefulness in which there is still no loss of consciousness and in which there is a feeling of tiredness, heaviness, sleep, dullness of the senses and awkwardness in movements “. This is determined mainly by four factors:

  1. The time of day: the late hours of the morning (between three and five or six in the morning) and the hours “of the meal ” (between two and five in the afternoon) are the periods of the day in the that usually appear the most clear symptoms of drowsiness. Despite the number of hours we have slept before the trip, these hours correspond to periods in which our body, usually due to circadian rhythms , usually finds itself sleeping.
  2. Environmental stimulation and level of activity of the driver: the trips made by a habitual road (monotonous) , by highways with great straight lines and without changes of speeds or curves and those that we do alone are the most dangerous, since to maintain a certain degree of activity during the same (talking to the companion, changing speeds, roads with curves in which we must always pay attention …) helps to avoid being distracted and drowsy. And not. Go talking on the phone does not help at all (well, the Civil Guard itself).
  3. Individual “performance” of the driver: there are people who drive better during the day and others who do it better at night, so we must try to make the trips in those hours in which we know or intuit that we are going to be within our full performance .
  4. Time that remains awake continuously: Obviously, the longer we spend awake continuously , the more difficult it will be to avoid falling asleep.

In addition, we must point out that to combat drowsiness the use of caffeinated or energy drinks can be counterproductive, since being temporary its effect, this can lead to overconfidence, relapse after a while and, as a consequence, have an accident (unfortunately this point I can confirm from my own experience)

Causes involved in the onset of sleepiness during driving

Without going too far into the details of each, some of the most common causes that can influence the onset of drowsiness while driving are:

  • Sleep deprivation : that is, not having enough sleep . Adults usually need to sleep between seven and nine hours, so sleeping less could mean an increase in the possibility of drowsiness during the trip (however short it may be).In addition, if this deprivation of sleep is prolonged over time, it can cause “chronic numbness”.
  • Fragmented dream : to speak of fragmented sleep we do not necessarily have to wake up. Sometimes, noises, lights or any disturbance external to us (sometimes even due to being under stress) can cause us to not reach the deepest phases of sleep , so we will have a “light sleep” even without getting to wake up and this will contribute to the phenomenon of fragmented sleep.
  • Changes in sleep schedules : normally people are used to sleeping at night and perform our activities for the day, so making a change in our sleep pattern the day before a trip can be counterproductive. For this, I personally recommend whenever possible to try to change this sleep pattern at least two days before the trip ( if we are going to travel at night , of course), to try as far as possible that our body adapts. At least it’s how I like to travel and what I usually do when I travel at night on vacation.
  • The use of substances with sedative effects : despite the infinity of advertising campaigns and information panels, even today there are many people who drive under the effect of drugs that, among other reactions, cause drowsiness (some because they are not read the prospect and others because they do not care and ignore it). And this is a very serious irresponsibility that can cause deaths on the road.Among these medications, some of the most common may be anti- asthmatics , flu medications or antidepressants. Among the substances with sedative effects we could include the consumption of alcohol or certain drugs, which cause similar effects.
  • Sleep disturbances : to link with the sleep section, we will talk about sleep disorders as one of the causes of the appearance of sleepiness due, as you can imagine to an alteration in sleeping patterns that will negatively affect our rest and therefore to our abilities to pay attention to driving and reacting.Insomnia , narcolepsy , hypersomnia , respiratory disorders such as sleep apnea or parasomnias , are some of the sleep disorders that can affect us while driving.

Consequences of sleepiness and its effect on driving

If we have not been able to anticipate and begin to suffer drowsiness during our trip, these are some of the consequences that we can suffer if we do not remedy it in time:

  1. Decreased concentration and increased reaction time
  2. Slow and sometimes clumsy decision making
  3. Increase in the number of errors in driving and maneuvers
  4. Emergence of the micro-dreams : periods of just a few seconds during which the person is slightly asleep and remains oblivious to what happens in traffic. They are one of the most negative effects of drowsiness behind the wheel and are related to numerous accidents of extreme gravity. The biggest problem is that they usually go completely unnoticed and we do not realize it until it’s too late.
  5. Alteration of the senses : when drowsiness appears, our senses are directly affected: the lights become more annoying for our eyes, we can partially lose sensitivity in the hands and feet, we do not control the distances equally …

The dream

By definition, it is ” the resting state in which the person or animal that is sleeping is, or the desire or need to sleep .” If we have reached this point, it is very likely that we have suffered or are very close to suffering a traffic accident.

Unfortunately, when we get to this point the consequences are usually already inevitable and result in traffic accidents (of greater or lesser severity, although as a rule they are usually almost always serious accidents) and, if they occur in urban roads can mean abuses of pedestrians or pedestrians .

Sleep apnea

The sleep apnea syndrome is one of the most serious diseases among the factors that can be classified within the sleep section. Said syndrome consists of the person suffering from it making stops in the breathing during brief periods of time during the sleep cycle or having shallow breaths.

It is usually a chronic problem, it causes a very bad quality sleep and, therefore, we spend the rest of the day tired and without the energy that we would have if we had rested correctly. In addition, the consequences caused in driving by this phenomenon are very similar to those produced by other substances such as alcohol and sleep deficit.

As significant data, comment that this disease tends to occur very often in obese people (as a direct result of overweight or obesity) and tend to suffer more men (about 24%) than women (about 9%).

Road safety

A subject and knowledge of road safety has been taught from the first courses for a few years in order to raise awareness of the importance of attending to the rules of the road for both drivers and pedestrians since the first ages. thus, accidents and victims who lose their lives as a result of distractions or recklessness could be drastically reduced.

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