Duel 1971

Where was the ending scene for the 1971 tv movie for abc starring dennis weaver filmed where his car goes off a cliff?

IMDB says 16948 Vasquez Canyon Road, Canyon Country, California, USA

It looks like it, and most other places, has been developed with houses.
16948 Vasquez Canyon Road

A bigger question: who was driving the truck that chased Dennis Weaver's character for days? (I don't mean the stunt driver for the film, but who was the mystery killer?)

I think the point is that we’ll never know.

I think it was Dennis Weaver - he was paranoid & delusional and caused the death of an innocent truck driver.

It was a guy named Dewitt Allen...he went by Dew Al for short