Me and my friend were there last week and we were thinking about the same thing. We couldn't quite remember, but we thought there used to be a black train as well as the red, blue, and yellow ones. Like I said, we couldn't quite remember, but that is what we thought. I was looking at the numbers on the sides of the cars and on one of the trains the numbers were 11-17, on another one they were 21-27, and on the third one they were 31-37. There was no 01-07 which could of been on the fourth train. This was just our thoughts.