From San Francisco: "Dad and lad ride all Muni lines," by Martin

When he was 4 years old, my son Max was really into Muni. He knew whether all of the buses we frequently rode were electric, biodiesel, or hybrid electric. When we got off the bus, he made me stop and watch it go, so that he could see if there was a spark on the wire, or if the bus “came off the track.” (Read more here.)