I remember watching a (maybe post-apocalyptic) sci-fi as a child, which featured an autonomous semi truck looking very similar to the one that Tesla motors presented. This part of the movie took place in surroundings similar to those of Mad Max, in that it was a desert like place.
A guy walked onto a road, stepped in front of this running autonomous cargo semi and the semi truck stopped and explained it was done based on a protocol programmed to save lives or something along those lines. The truck told the main character to step aside to allow the truck to continue. Then the main character somehow managed to hitchhike it, and got to a city I think, the rest I don't remember.