When i first heard about the movie i wondered what practical reason there would be to maintain the last human society after the apocalypse in a constantly moving train. And it turns out there is no practical reason. And really no practical way it could work. It makes a good metaphor for the "social commentary on the classes of society" theme and it lets them tell a particular kind of story with many different striking scenes, but that's it.
Also, did i mention the darkness and violence? The movie starts with 99.9999% of the people on Earth dead and only goes downhill from there. Do not go see this expecting a cheery ending for everyone.
Avalyn compared it to Reservoir Dogs, which i haven't seen so i can't comment on that. The style seemed a bit like Blade Runner to me, except even more dystopian. Oh, and i guess a little bit of Hunger Games, especially with the Tilda Swinton character. I think some people have compared it to Elysium because of the social commentary thing. I haven't seen Elysium but from what i understand even if the comparison is vaguely accurate the moral of Snowpiercer is a lot darker than the one of Elysium.
After acknowledging exactly how impractical it all is, i am still curious about the actual dimensions of the train however.
I'm not sure if we ever see both the front and end of the train at the same time. It's definitely at _least_ 20-30 cars long based on what we see them traveling through but i expect it's actually much longer. I've seen some references to the train being a mile long, which if we assume cars about 80' long would be about 60-70 cars. Apparently in the original comic the train was supposedly 1001 cars wrong, although i'm not 100% sure if that was intended as a literal or figurative statement. That would put it at about 15 miles long, far beyond anything seen in the real world. And would also mean we only saw interiors for about 2-3% of cars. That's certainly a ginormous train, but from a practical standpoint it would make sense to have about 100 farming or industrial cars for every single car of people. And from a dramatic perspective it would make sense for them not to show very many of the repeating unpopulated cars.