One can easily foresee a future where a self-driving truck has a driver in it who is only driving 'regulated' hours for a small portion of a trip (say during high traffic, highway entry/exit, etc). The driver could spend the rest of his time sleeping, reading, or coding - he'd basically be a passenger.
If a truck can haul for 20-30 hours without stopping for overnights, that dramatically changes the economies of fast freight.