I was talking about this film last week with a friend who'd shipped his Harley over to do Route 66 (or at least what's left of it) and he was telling me about one section a couple of miles long that really bad, some sections were little more than potholed dirt tracks where he was down to a walking pace with his feet down in case he lost it on the loose surface.
In his mirrors he could see a typical huge American rig, just sat behind him at a constant distance. Even when there was plenty of room for the rig to pass, it still sat behind. Whenever my mate stopped to let him pass, the truck stopped as well and when he pulled away again...so did the truck.
After a while all he got a bit concerned and started thinking of that film 'Duel'.

He was rather relieved when he got onto a good road surface and the truck roared past with a couple of short blasts on it's horn.
Fair doos to the driver, he must have stayed behind my mate in case the bike went over and would be able to help him lift it upright again.