This (falling asleep at the wheel, not getting a company car as a tax
dodge, alas) is the theory that makes the most sense to me about a
trend I've seen out in the wide open spaces of the western US.  I can
hardly take a long road trip without seeing the aftermath of an
otherwise pretty inexplicable and often high-energy single-car
wipeout.   In one instance I was the first on the scene and discovered
that that was what had happened.  They were coming back from a weekend
of riding motorcycles in the desert, dozed off at the wheel, and, as
you said, "Boom!"    This discovery was in the dim light before dawn,
as I was just getting back on the road.

In that case, everybody was alright, though their pickup truck had
been stood on its ear and was a bit wrinkly -- -- when I left, they
were attempting to push it back onto its wheels, presumably to get out
of there before the cops showed up.   In other cases, what was left
was a meatball at the bottom of an embankment or stubbed up against
some large hard obstacle, and it was pretty likely that everyone was
not alright.

Of course, alcohol and sleep deprivation go together like tow trucks
and ambulances.

The five days cited in the original posting sounds like overkill for
most people.  By 36 hours without sleep I'm seeing things, and have
long since passed the point where I have any business behind the
wheel.

A key warning sign is the advent of  "microsleep" -- the feeling that
you just lost an infinitesimal slice of time from your consciousness.
There are other earlier warning signs (wandering attention, big yawns,
difficulty figuratively and literally focusing...)  but microsleep is
final notice from your body that a motel or rest area or a safe-
looking turnoff would be a *very*  timely discovery.    Keep pushing
it too long and you risk going into plain old macrosleep and waking up
in the ditch... or not at all.

--Joe