Pigs
We watch as Chihiro's parents are turned into pigs when they eat food meant for the spirits. This imagery shocks Chihiro, and as an audience we recognize the reality of overconsumption when we eat from the things that don't belong to us. And just like the parents who are now pigs, they cannot stop consuming.
Spirit Train
We see Chihiro dropped off at the tracks which lead to the spirit train. There is water covering the tracks and this water connects to a vast amount of natural water that she had to be brought over on by boat to reach the tracks. With these two elements Miyazaki uses the train tracks as leading lines towards the clouds in the sky. This single image reveals to us that Chihiro is heading into a place that is not quite understood by the natural world. It belongs to it, but at the same time exists apart from it, and we get the sense of this from this imagery.
One Way
We watch as people get off at the train station, but they are transparent and dark figures. This imagery creates for the audience a sense that Chihiro is in a place that is undefined by the natural world. Though it is not clear where these people are, it creates the idea that, for many, what exists after death is a mystery until we experience it for ourselves.
Ma
Miyazaki talks about the term, "ma" which means emptiness. This space is intentional in his films and in Spirited Away this "ma" occurs most significantly on Chihiro's train ride where there is no dialogue or plot progression. It is an opportunity for us, like Chihiro, to experience a moment of reflection about where she's been, to be still in where she is and to look forward with space towards what's next.
