In stop-and-go traffic on 395 this woman kept making faces at me in her side mirror, as she swerved all the way onto the shoulder and back. She did this three times. It was only at the third time that I realized she was telling me to back off, even though I was no closer to her than she was to the car in front of her. We were only going between 5 and 10 miles an hour during evening rush hour. There is clearly something wrong with her perception.