Quote Originally Posted by pomtzu View Post
Perhaps it's just that you find driving more boring than you used to, or the routes have been driven so many times that you could almost drive them with your eyes closed. Boredom can definitely lull you into a sleepy state.
Could be I5 connects northern california to southern california and its basically a straight 4 lane highway of nothing the twisty roads from the coast kept me awake but I get sleepy at my desk in the afternoons too and that is boredom too.