To me, this is something of a gloomy story about how people are powerless in the face of what their governments want to do. They lead lives that are weak and oppressed -- they can't really have an impact. Things happen to them and they can't stop those things, no matter what they think of them. I think this is symbolized to some degree by the setting.
The people are on this old-style railroad car and it is just sitting there, going nowhere. It is a very stale atmosphere. It is oppressive and stuffy as you say. This shows how dull the people's lives are.
So the train and the inside of the car show the futility and powerlessness of the people's lives.