A driver may feel **drowsy** even if they have slept the necessary hours, if the **quality of rest has not been good**. This is because drowsiness is not only related to the number of hours of sleep but also to its quality. Poor sleep, even if for many hours, can cause drowsiness. Other factors that may contribute to this state include changes in the usual sleep schedule, driving at times of the day prone to drowsiness (such as early morning or after eating), and the consumption of alcohol or medications.

Drowsiness manifests through several **symptoms** that can affect driving ability, such as difficulty keeping the head upright, blurred vision, frequent yawning, and loss of concentration. These symptoms can appear before a person falls completely asleep, increasing the risk of traffic accidents. Therefore, it is crucial to recognize these signs and take measures to ensure quality rest before driving.