What makes us tired in a car if other passengers are sleeping?

Are You Always Tired? 33 Reasons You're Tired All the Time

Driver fatigue: why does driving make you tired and how to avoid it – Engage Driving

Drowsy driving is a major problem all over the world. The risk, danger and often tragic results of drowsy driving are alarming. Drowsy driving is a dangerous combination of driving and sleepiness

CHP: Drowsy driving is dangerous driving

Dash cam video shows semitruck driver apparently falling asleep before crash

If you are sleepy, park and take a nap

Why You Feel More Tired When Your Sleep Is Interrupted

Tips for Sleeping Comfortably as a Passenger in a Moving Car – UnbuckleMe®

Driver fatigue: why does driving make you tired? - Optalert