I believe this is the movie mentioned above:   "DUEL".

Both the original short story and the screenplay were written by Richard Matheson. I recall reading it in a magazine a few years before the movie appeared. The movie was directed by Steven Spielberg and I believe it was made for television. That's where I saw it.

Dennis Weaver starred, and the villain was a rusty old tanker truck that began to take on the character of a prehistoric monster. You never get a look at the driver of the truck, other than his left elbow leaning on the window of the truck's cab and one scene in a gas station when you see a pair of booted feet walking around the truck and kicking the tires—waiting while the protagonist finishes his lunch at a nearby lunch counter. Toward the end, when the protagonist decides he's not going to take it anymore, it begins to take on the aspects of a bull fight.

A real white-knuckle thriller!

Here is a full detailed synopsis of the story: CLICKY 2.

BEWARE. SPOILER ALERT!

Don Firth