Way back when(mid-late 70's) a big-for-the-times guy fell asleep while he was moldboard plowing with his 130-06 Deutz and plowed right across a town road. Through both ditches and 2 lanes of blacktop. Couldn't even blame the help, it was the boss driving.

I have dozed off and woke up just in time a couple times. It can happen plenty easy.