These companies running these robot rigs will need, and likely get, liability exemptions. The first time -- and there will be one -- one of these robo-trucks kills somebody's Aunt Bessie or somebody's children, lawyers are going to be parachuting in to handle that case. If liability exemptions aren't in place by then, they soon will be.
It could work exactly opposite. The robot cars on the road now have logged hundreds of thousands of miles, if not millions, and there has not been a single accident ... not one ... when the car was driving itself. There was one fender bender when a human operator was in control of the robot car.
In the event of a tragic crash in the future, the legal liability question may be, why were you permitting a human to drive your truck when you knew or should have known that a self-driving truck is much, much safer?
While driving, robots don't take their eyes off the road to change the radio station. They don't light cigarettes. They don't get angry because someone cut them off, or get tired after a number of hours behind the wheel.
They don't make freeway lane changes, exits and entrances for bathroom stops. They always signal their turns. They don't text or make and receive cell phone calls in a way that distracts them from driving. They can see as well at night as they can in the day, and they can see through fog.
Their on-road time and exposure is minimized because the only miles they drive are work related. They don't have to drive extra miles to get groceries, go in for a drug test or for any other personal reason.
Having no hours of service issues, they can schedule their driving to blend well with traffic flows. It does not matter to them if a route goes through a bad neighborhood, over a rough road or involves lots of traffic lights. Once underway, they can drive as long as their fuel supply allows. They have no need to find and use parking places on their route, eliminating the risk of being hit by another truck while parked at a truck stop.
Getting stalled in traffic does not upset them. They don't care if they get home. They don't care if they have to wait hours at a dock or days for a load. They don't get upset because their girlfriend said something wrong.
While driving, their minds don't drift. They don't become preoccupied with with a ball game they are listening to on the radio or a CB radio discussion or the pretty girl in the four-wheeler nearby. They don't worry about how to pay for the the kid's braces or the fight the wife is having at home with her live-in father-in-law who is there because he can no longer take care of himself.
Robots don't drift out of their lanes. They don't tailgate. And they don't get lost. If an emergency stop must be made, their reaction time is faster than any human's.
If a safety or maintenance issue develops on the vehicle, the robot will detect it and, instead of continuing to drive to deal with it in a way that is convenient to the driver, will take immediate action as appropriate to the issue.
Liability-wise, humans present the greater risk.