2)self driving trucks can pay for themselves just by having the truck on the road for more hours of the day. Laws prevent drivers from driving too much in 1 day. If the driver could legally sleep in the cabin for shifts, you can reduce overall costs a lot (without going full automation).
And then I think the next step after that is to have local humans meet the trucks right off the highway, sort of like how pilot boats meet cargo ships and guide them into port. The truck cab stays empty for most of the run, and drivers get to sleep in their beds each night.
Plus, highway driving is safer and cheaper than average so the bar is higher for self-driving cars/trucks.
I don't think there's any middle ground for driving semi-trucks on the freeway. It's either safe enough to drive without someone watching it or it's not. There's no point in having a person in there sometimes sleeping and sometimes safety-driving.
1. Urban navigation. Obviously the end game, but just exit to exit interstate navigation would be a much better near term goal and greatly benefit truck drivers along with anyone doing a road trip.
2. Unmanned. I would think it would be a long time before you would have unmanned trucks going down the highway. Seems much more obvious to have a driver / custodian in the truck for the foreseeable future until everyone is very comfortable with the reliability of the tech and its ability to cope with situations like you describe. Meanwhile for truck drivers to get around mandatory rest periods due to self driving assistance would be a huge win for the industry even if they are still manning the truck.