Have you ever driven an 18 wheeler? I have, people are afraid of them now and you want unmanned trucks?? Highways are not straight they turn, they go, up they go down, they get wet, they get snow on them, they get ice. Trucks get flat tires,Engines break down ever try to control a loaded 18 wheeler that had a front left tire blow out? Oh wait they wont need tires??? We will never have unmanned 18 wheelers as long as we have railroads now there is somewhere it might be possible for unmanned deliveries they have there very own highways.