When I was in college in the early 1990s, I had an experience driving home around 1:00am-2:00am on Interstate 694 in the eastern suburbs of Saint Paul, Minnesota. It was late, and I was essentially alone in the middle lane of a multi-lane south-bound freeway (no other cars within several hundred yards of me). Without warning or any on-/off-ramps, a car suddenly appeared within feet of my rear bumper with headlights shining brightly in my rear-view mirror. I was immediately concerned about gang activity or other potential dangers, but I could not exit the freeway... So I simply kept driving.
After several seconds of the car literally being 4-5 feet behind me, it violently swerved to the right-hand lane (to my right) and pulled alongside of me. I cannot remember the exact type of car, but I do remember vividly the dark color and "beat-up" appearance, along with the words "The Beast" written into the driver's side door. I also remember that the driver of the vehicle looked like a much bigger, more evil-looking version of Marilyn Manson.
Now I was frightened, but I did not know what to do, as I had no way to exit the freeway. I just kept driving. After several seconds, the car promptly braked and got directly behind my car again, and after a few seconds of tailgating me (with no on-/off-ramps available), the car just disappeared. The freeway has lots of light poles in that stretch of road, so I know it was not simply an issue of the car turning off its head lights (as you would still have been able to see other vehicle in front or behind you). The car was simply gone.
To this day I have not been able to explain the experience.
I can't speak to the credibility or validity of the Warrens, but what you describe certainly struck a chord.