The second half of Snowpiercer was more, not less, claustrophobic than the first

Scott Kaufman, writing for A.V. Club:

The first half of the film is profoundly claustrophobic in a conventional way, so much so that the eventual presence of light becomes a crucial, if brutal, plot point. The latter half of the film, however, is just as claustrophobic, just not conventionally so. It doesn’t “avoid claustrophobia”—if anything, it embraces a more oppressive version.

Good read. Interesting to see things like this picked out when my brain didn't do it for me as I was watching the film.

Also you should probably watch Snowpiercer right now.