Uh, they're called trains.
A Vision Of A Driverless FutureThere may be big truck-like things that travel in convoys, but there will also be transportation vehicles that function essentially like interchangeable, road-based shipping containers, with no dedicated space for a person. Indeed, someone might even develop something like container “skates” that you just roll a container onto as soon as it comes off a cargo ship, or out of a factory, helping the thing zoom along roads to its programmed destination.