1.  You could fall asleep at the wheel and kill yourself (or others).

2.  You could be driving along thinking about how tired you are and not about which freeway exit you want to take, and all of a sudden you’re faced with a choice–East, West, North, South–and you won’t remember which the hell it is because it’s almost 1 a.m. and you just…don’t…know, even though you’ve driven this route many times and have always made the correct decision before–seriously, it’s not that hard–but right now, for some reason, you’re thinking, “East…west…whuzza diff’rence…who cares…” and then you remember, “WAIT!  WAIT!  THERE IS A DIFFERENCE!  I CARE!  BUT WHICH IS IT?  WHICH IS IT?  IT’S EAST!  NO, IT’S WEST!  IS IT WEST?  YES, IT’S WEST!  WHICH WAY DID I JUST GO?  WAS IT EAST?  IT WAS EAST, WASN’T IT?  CRAP!”  Which wouldn’t be such a big deal, except that when you’re going east, the next freeway exit isn’t until, like, Idaho, and as lovely as Idaho is this time of year, it is very far removed from where you need to be, which is in bed, sleeping.

* Note:  I didn’t really have to drive all the way to Idaho before turning around and heading west.  That was an exaggeration, for dramatic effect.  In reality, there is at least one exit between Portland and Idaho.  Unfortunately, it drops you off in the middle of ##$*(#$ nowhere, where there are no street signs–not that it matters because there are no streetlights, either, and it’s pouring down rain because it’s Oregon, so you wouldn’t be able to read the signs even if they were there.  On the plus side, you are starting to wake up.  On the minus side, you feel pretty much ready to kill yourself (or others), which is also dangerous.  Incidentally, where you read “##$*(#$,” I want you to think of the filthiest word you know, because even if it wasn’t the word I was saying last night, it was certainly the word I meant to be saying.

And that’s why you shouldn’t drive when you’re really, really tired.  Tell your friends, etc.