I grew up with the driver, Eric Hager, and was still good friends with him when he died. From what I remember of the time, he had seen the dead in DC and was heading back to Columbia, SC where we went to Univ. of South Carolina (so I-95 would have been more likely than I-85). I don't know if he visited his father but I *think* his dad lived in the Norfolk/Virginia Beach area.
His mother and step-father lived in Inman, SC (technically but actually Boiling Springs/Spartanburg, SC) but he was living in Columbia.
Nobody in our group of friends knew at all the rider who was with Eric. If I were to guess I would say it was a hitch-hiking deadhead going to the next show.
If there is any other info I might be able to offer, feel free to ask. It's been such a long time I'm not sure how much I can remember.