It started when he was a kid. His parents were all like, "Isn't that cute, Brian loves trains and cars." But as he got older, it became less cute. His obsession with cars has put him in the poor house. He moved to NYC and continually tries to trick everyone into going to the Transit Museum. Don't get him started about that Law & Order: SVU episode about the people who live under the subway, or his theories about what REALLY happened to Amelia Earhart.
His love of things that move people from point A to point B is pretty quirky, but so is your love of Designing Women, amiright? Don't judge.