I like trains. I live in Bakersfield. When they started naming the cities where the murders occured, I remembered going through those cities by train. Modesto, Fresno, Bakersfield... When the agent made the local police withdraw their nickname of the Highway 99 Killer, it made sense to me, because while Highway 99 runs parallel to the train tracks, the name would draw attention away from looking at the trains as a possibility.
My grandparents lived near train tracks and sometimes when I'd sleep over at their house, I would hear the train whistles at night. Such a lonesome sound. They used the sound on Criminal Minds and it brought back those memories. I also liked the hobo jungles, and the signs they drew on houses with secret meanings so other hobos would know where to get a hand out. I have seen those signs drawn on my grandparents house and wondered about them.
There was one loose end on this episode that I wondered about: The black agent with the shaved head was trying to pick up a woman in a coffee house, but not only did she observe that he poured his coffee out in order to get back in line behind her, she also knew his name. Just when I thought that they had dropped the thread, she shows up as a new agent who will be working on the team.