What visual sign can indicate that a driver is becoming fatigued?

A driver showing heavy eyelids is a clear indication of fatigue. When a person is tired, the body naturally reacts by causing the eyelids to feel heavy or droopy, which can lead to reduced awareness and slow reaction times. This visual sign is particularly concerning because it suggests that the driver may not be fully alert and could struggle to maintain focus on the road.

In contrast, wide open eyes typically signal alertness and not fatigue, while frequent blinking can be a normal response based on various factors, such as environmental conditions or eye strain, rather than a direct indication of drowsiness. A head held high might suggest attentiveness or good posture, which does not correlate with fatigue in a way that would influence driving safety. Recognizing the signs of fatigue is vital for maintaining road safety and preventing accidents caused by drowsy driving.