Highway is simpler but it's worse if it goes wrong. Plus, highway driving is safer and cheaper than average so the bar is higher for self-driving cars/trucks.

Highway is simpler but it's worse if it goes wrong. 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.