Movement of the people.
Oh yeah, this year there will be 60 thousand burners. And when they all decide to drive out sometime between the temple burn and Monday night, down a crappy country road at just over 2 miles per hour, it will be a complete mess.
There’s only one legal exit to the playa, and it’s only one lane. You will be correct when you imagine the bottle-neck is pretty bad. Generally it takes 5 or 6 hours in line to get off the playa, then perhaps another hour to get far enough away that you can get up to speed.
So bring enough gas and supplies to survive Exodus.
Keep yourself hydrated, even though you are leaving, you’ve got a lot of hours before you manage to hit a town.
LNT doesn’t stop at the trash fence, haul your trash all the way out, and dispose of it responsibly, preferably somewhere that isn’t completely overwhelmed with burner trash.
If you must pull over, or break down, get all the way off the road.