I usually dont have that problem, almost every person in my family is a truck driver so It runs in the familly.
But there are the rare ocassions when I start to dose off, I just roll the window down and stick my head out leting my hair and lips flap in the wind like a big ol' saint Bernard. (If you drool it helps even more)
Just a thought.
Be carfull man we dont need no dead folks on here.