It was only when I saw a short scene from the "Duel" (1971) from Steven Spielberg again that suddenly something come into my mind.
You see those car plates in front of the truck? I simply thought during the film it was like those other decorations people have...fox tail on the antenna, stickers, talismans.
Did the truck driver collected the car plates from former victims and present them openly as trophy knowing that very few (likely the next victims) will recognize their purpose?
The thing is: In the movie David never mentions it, even not in the monologue while being in the cafe after chased. Can someone verify that it is in fact intended by the script?