First, a confession: I have driven when I was sleepy, really sleepy.
Now, your turn. Chances are you too have driven while drowsy. Sleep researchers at the Liberty Mutual Research Institute in Hopkinton, Mass., estimate that every day 250,000 Americans drive while sleep-deprived.
According to National Highway Traffic Safety Administration figures, more than 6,000 people are killed every year in vehicle accidents blamed on an exhausted driver behind the wheel. That's second only to drunk-driving fatal accidents and ahead of those attributed to driver distraction, which includes texting.
For someone operating a motor vehicle, sleep deprivation can be as dangerous as driving intoxicated.
Just one sleepless night or chronic sleep deprivation causes all kinds of problems, and not just while driving. A lack of adequate sleep affects a person's judgment, memory and emotional mood.
A recent study reported in the Journal of the American Medical Association put the annual dollar figure for workplace accidents associated with sleep deprivation at $31 billion.
If you go onto YouTube you will find plenty of videos of workers snoozing on the job. They're usually played for laughs -- like the video of a New York City subway worker sound asleep while the people videotaping cackle hysterically. But being exhausted at work or while driving a car is no joke.
"Sleep is such a powerful drive," said Dr. Meir Kryger of the Yale Sleep Medicine Clinic in New Haven, Conn. "If you need it, the brain will say 'Sleep' and that can be an incredibly dangerous situation."
Experts say most people need seven to eight hours of sleep a night. If you're one of them and you aren't getting it, you could fall asleep at work -- maybe not that big of a deal if you have a desk job (aside from embarrassment if your colleagues catch you at it), but if you're operating heavy machinery or driving a 2,000-pound car at 60 miles an hour, you've got a problem.
In addition to the prospect of falling asleep, there's another, insidious phenomenon called micro-sleep that can happen when you're very tired.
Micro-sleep occurs when you nod off for a second or a few seconds, often without even being aware of it. In some instances, your eyes may even be open and you can perform a task as if on a kind of auto-pilot, but you're asleep.
"Micro-sleep is a brief transition from wakefulness to sleep and it can last up to maybe 20 or 30 seconds," said Dr. Charles Czeisler, chief of theDivision of Sleep Medicine at Brigham and Women's Hospital. "You're awake and then suddenly you're asleep."
I wanted to learn more about the effects of sleep deprivation on driving and to experience for myself. So, an ABC News crew and I traveled to the institute's offices outside of Boston. Before we arrived, I stayed awake for 32 consecutive hours to mimic the effect of a sleepless night or chronic sleep deprivation.
At the lab, I was hooked up to a brain wave monitor and a device that tracks eye movement.
Then, I got behind the wheel of the researchers' minivan.
My assignment: to try to drive on their closed track for two hours while members of the research team rode inside the vehicle with me and studied my reactions.
As tired as I was, I still thought I would be OK. After all, I'd pulled many an all-nighter in college and many more in my years as a reporter.
But I hadn't driven 10 minutes before I felt myself fading.