This is my subway breakdown for TMNT2: Out of the Shadows. I was tasked with creating almost the entire shot (sans the Turtles on top of the train not seen in this breakdown). I had a lot of help from Sonja Christoph who had a great subway asset that I used to spring-board from.
The tunnel was created by modeling a smaller chunk (about 20 ft x 20 ft) then duplicating it about 20 times. When tasked with creating the passengers we though it would be better to use 3d scans of people rather than digital doubles. I made scans of various people in the 3d Generalist department at ILM. They were very quick and rough but its all we needed to sell the realism. They were slightly animated with soft fall off modifiers.