It's a little more complicated with a truck. First off, people will be - rightfully - wary of an autonomous 80,000 lb., 13.5' high, 70 ft. long vehicle. Not just the general public, but owners and insurance companies. The slightest screw-up with a vehicle this heavy, and someone's gonna die, or something will be destroyed. And simply going down the interstate is the easiest part. What happens at the last mile of the trip? I can tell you, as a truck driver, that my Garmin truck route GPS is almost always wrong when it comes to these industrial areas that I have to go to. It'll get me in the vicinity, sometimes within eyesight, but even when it's occasionally spot on, that's often the main gate. I still have to figure out which gate my load goes into, which is often on the other side of the plant. GPS is going to have to get a lot more accurate than it is in these outlying areas.
Trucks have to make some fairly complicated maneuvers, and go into some tight spaces, while loading, unloading, and fueling. And as often as not, this occurs on dirt roads. A human being has a hard time doing this stuff until they have about a year's experience. You can't imagine how easy it is to get jammed-up in these vehicles, by simply making a wrong turn, or miscalculating how much space you have, and how hard it can be to extricate yourself.
If it would work at all, it would likely only be feasible for freight trucks (dry van or refrigerated). Even there, many shippers and receivers are set up where, instead of backing into a dock, you drop an empty/loaded trailer, and grab an empty/loaded trailer. That can't be done autonomously. Shipping containers might be able to be loaded somewhat autonomously, but you still need someone on the ground, if only to flip and tie down the locks. And, of course, the entire port would have to be modified. The whole freight infrastructure of the country would have to be modified to accommodate autonomous trucks, and in many places, such as cities, it wouldn't be possible.
Other types of trailers - dump trucks, tankers, bulk trailers, flat beds - need an operator who's familiar with the equipment. I could see in some cases where some shippers and receivers could keep full-time loaders and unloaders, but they would probably have to be truck drivers as well, to maneuver the truck into place. I can't see letting a tanker full of some hazardous material trundle along on its own through a chemical plant. You'd have to hire people to do everything a truck driver does - loading, unloading, fueling, and inspection. Flatbed operators have to tighten their straps or chains (at least) everytime they stop. Straps loosen as you drive, and sometimes break or come off. Who's gonna keep an eye on that?
Trucks require, by law, at least one daily inspection. You might be willing to allow another company's employee to do the loading and unloading, but since you, as the truck owner, are responsible (liable) for the truck's safety, how is that going to work? What happens if the truck breaks down, as they very often do, and there's no driver? They're complicated machines, and with the addition of computers, getting more complicated. There are too many things that can go wrong, and you need someone there who can figure out what to do.
tl;dr - Driving a truck is nothing like driving a car. In the end, I think they'll keep a truck driver aboard, even if he's not always driving. It's by far the simplest and cheapest solution.