**Drowsiness** is a state in which the driver feels **tired and heavy**, which can affect their ability to drive safely. It is not necessary to fall completely asleep for an accident to occur. Symptoms of drowsiness, such as the feeling of sleepiness and fatigue, can appear **before falling completely asleep** and are already enough to increase the risk of an accident.

Drowsiness can be caused by several factors, such as sleeping fewer hours than usual, changing sleep hours, sleeping poorly, driving on roads with little traffic, consuming alcohol or medications, having sleep-related illnesses, and driving at times of the day such as early morning or after eating.

Therefore, it is important to recognize that accidents can occur **before the driver falls completely asleep**, due to the effects of drowsiness.