virtuosovillain:

“The most important keyword to me was ‘train’ and the structure of the narrative reflects that. It’s simple: Curtis travels from the very last section of the train to the front. So the different carriages represent different stages in the story – every time you enter a new car, it’s like a new world that the characters are experiencing." 

– Joon-ho Bong on the design of the train cars.

(Source: jimprideauxs)