> Cutting them off, getting closer to them, slowing down in front of them, etc.
My brother is a lorry driver who frequently crosses the Turkish - Bulgarian border with his truck (as in once every 2 weeks). Once or twice he caught refugees (or whatever you want to call them) trying to get inside his trailer by cutting through the thick textile material that covers it, while he was awaiting at the border. You generally do not whant people mixing with your industrial equipment while the truck drives at 90-100 km/h. In other cases it happened to him that other people had stolen diesel gas from his tank while he was asleep during the mandatory break (this happened somewhere in Western Europe, I forget where).
And leaving aside all this, assuming that bad people won't suddenly stop stealing and generally doing bad stuff to unattended expensive material (like trucks and the things that the trucks carry), being a truck driver you're also doing lots, and lots of bureaucracy work. I once shared the cabin with him as a passenger during one of his routes, while we passed two European borders. The amount of paperwork he had to fill in was mind-blogging, I half-jokingly told him that his job looks more like a clerk-job than being an actual driver. Now, lots of clerk jobs have already been automated, I know that, but it mostly happened in the private sector, inside private companies doing business with other private companies. But once your clerk-like job involves having to do business with several State-like entities things become a lot more complicated, with legislation changing once every 6 months, being very diverse from State to State etc.
What I'm trying to say is that theoretically the self-driving problem looks achievable for trucks, but once you get into the messy details things become a lot more complicated.