Honestly the self driving truck is a huge liability. Who gets sued when they cause carnage? Who gets a prison sentence?
These are really good questions and their solution is part of the reason why self driving trucks are not universally available today.
The short answer is that these answers are being evolved through discussions between OEMs, insurance companies and regulators.
Keep in mind that your questions are also applicable with human drivers. It is a known fact that human truck drivers can cause "carnage", can be a "huge liability" and are subject to "prison sentences". Remember that there are 1.3 million deaths every year globally on roads today caused by traffic accidents and truck drivers are involved and at fault here too.
AVs have the potential to reduce this death toll substantially. A human truck driver may well be on a deadline to deliver goods and is subject to anxiety, tension, distraction, anger, road rage, drunk driving, etc. An AV robot is not subject to anxiety, tension, distraction, anger, road rage and drunk driving. I recall that when Google began testing AVs in 2009, they said one of the major reasons they were pursuing self driving vehicles was to solve an unmet human need. 1.3 million people die every year, mostly as a result of human error. 1.3 million deaths per year is the same as a Boeing 737 jetliner crashing and killing its occupants every day of the year. If you read these deaths as Boeing 737 jetliners would you believe society and regulators would allow Boeing to build commercial aircraft? Hence there is a real problem on the roads today with human drivers and a solution with the help of technology can be found.
As for AV trucks, note in the link I provided above regarding the Foxconn plant being built in Wisconsin, they are planning AV truck use carefully. Yes they are to be used on public roads but they are planning the roads and street lamps and sensors and LIDAR to be interconnected to achieve safety.
If you have a few minutes, listen to this recent TED talk about How Self Driving Cars work (same concept for trucks) and you may come away more positive about the chances of successful implementation.
https://www.youtube.com/watch?v=Ly92UcnoEMY
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