When doing long trips, you will eventually start getting 'tired' in game. This is shown to you by a message that takes up your GPS space saying "You are getting tired. You shold find a parking place to rest".
I have noticed that the screen will occasionally start blacking out but I have always rested before it got too bad.
Once this message starts showing, how long can you keep driving until you fall asleep?
Do you actually fall asleep at all?