If I’ve learned anything from the book The Promise of Sleep by Dr. William Dement it is to never drive while sleepy. While one may think that one can stay away, the book gives many examples of cases where the driver was not able to (despite thinking that they were okay).
Even when one goes to bed at night, it is quite difficult to predict the exact moment we fall asleep. It just happens and it is very fast (like a light switch). There may not be much warning when that switch is flipped. This is exactly what can happen when you drive sleepy. One moment you are awake, and the next moment you are not.
Dr. Demet gives plenty of example of sleep-deprived drivers getting in terrible accidents (some even accidentally killing their passenger spouse).
He writes …
“If you remember nothing else from this book, you must remember these stories and the extremely important principle they are intended to illustrate.”
and also …
“… one very simple life-saving principle should be embraced as gospel truth: If you become drowsy at any time during the day, you have a sizable sleep debt and you should resolve to be cautious in hazardous situations.” [page 226]
He is referring to driving as a chief among these “hazardous situation”.
For himself, he writes …
“When I’m driving and I begin to feel the desire for the delicious relief of falling asleep, I immediately feel intense terror and alarm. It is as if someone has pointed a gun to my head. The indelible memories of stories and photographs of dead children on the highway flash through my mind. I have vowed that I will never be the cause of such an accident. I always pull over and take a nap” [page 228]