Presumably, the Snowpiercer drove in a circular pattern since it had been running for 17 years prior to the events in the movie. At one point, the creepy woman with glasses who seemed to be at least partially in charge mentioned that the nose of the train, when breaking through ice laying on the tracks, turned that pure snow to water, which was needed for the passengers. However, surely there would have been a safer way to collect water than risk a derailment by plowing through an ice-covered track.

Was any other reason given for why the train had to stay in motion?

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    Just a guess as I haven't seen it, but so it wouldn't freeze solid (along with all of the people inside)? – Pᴀᴜʟsᴛᴇʀ2 Jul 10 '14 at 18:27
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    Because that's what trains do. If it were to remain stationary, then what's the point of a train? A building would suffice, like one of the mega blocks in the movie Dredd. – Mrchief Nov 24 '14 at 14:46

10 Answers 10


IF the train were to stop moving, then the movement forward could take place outside the train. ie, people could exit in the back walk to the front of the train, and try to revolt by breaking in. (even if they could only survive outside for a few minutes) By keeping the train moving, the only way forward is the single passageway within the train, making maintaining the social order and status quo far simpler.

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    This is the only answer that actually addresses my question simplistically and realistically. Thanks! – Johnny Bones May 17 '17 at 14:48
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    Hmm. But it's made quite clear in the film that the reason for the train to keep moving was to sustain itself and the life within. An example is, the movement allows for outside ice to be melted into water for consumption. Stopping the train would lead to all systems (like heating) to shut down and the death of every passenger. The moving train is not to keep the revolt at bay, it's more a result of the in-movie science as many answers here are talking about. – John Jan 31 '19 at 2:23
  • Agreed, this answer doesn't make sense. Aside from what John mentioned. Outside the train is devastatingly cold - enough to cause someones arm to break in to a thousand pieces from a small mallet hit. Although we don't know until the end that outside is semi-livable, the occupants wouldn't have known that and they would have just assumed going outside meant death. – Alex Sep 29 '19 at 5:19

The big deal about the 'miracle of the train' was that it was perpetual motion engine: if it were to stop, it would no longer be contributing the momentum necessary to maintain its forward velocity...

As for Why the train needed to keep moving in the first place: the entire film is a parable about society, from a dystopian perspective. In the event of a global crisis, an ultra-efficient system is created in microcosm of the society it was spawned from. With each noseward carriage the revolution passes through, the higher standard of living and thus class they experience.

The train must keep moving to keep this system in place: if it were to stop, there would be a problem with the current status-quo, and thus an examination and potential change of situation, which would not suit those currently at the front of the train/ruling class.

Sorry its such a short answer, but this is kinda covered within the film itself.

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    That IS the narrative of the film, it's nothing to do with opinion, it's all explained throughout the movie: particularily the classroom scene... it's kind of hard to miss. Are you a non-english speaker? Could you have possibly seen the movie with badly translated subtitles? I'm not trying to be condescending, it's just that this is literally the central conceit of the movie. – John Smith Optional Jul 11 '14 at 16:59
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    So its an allegory: the train has to keep moving otherwise it stops, the ruling classes want the train to keep moving because it's always been moving, that is the state of affairs they are accustomed to and they're happy with things as they are because* they remain in power*. They brainwash, indoctrinate and propagandize the train's citizens that things have to remain as they are otherwise ( in your best teacher/Alison Pill voice) "everybody dies!" – John Smith Optional Jul 11 '14 at 17:47
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    The train has to keep moving because that is its purpose: its a metaphor for progress... but the film is saying this progress is an illusion that secretly only upholds the status quo, leaving 'the 99%' to suffer, believing they are contributing to a benevolent cause. They believe the train must keep running because they think there is no other way: Minsoo, conversely, believes there IS another way, outside of the train/societal system. If the train stopped, there would be no sense of purpose to keep everyone in their place.. – John Smith Optional Jul 11 '14 at 17:52
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    @John - he's asking from a true physical sense, not an, "I'm letting the movie teach me a societal lesson" sense. – JoshDM Aug 5 '14 at 19:57
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    "from a true physical sense" = there doesn't have to be a reason. As John points out, it's symbolism. There isn't a physical reason. There's an artistic reason. – DA. May 26 '15 at 4:56

The director of the film; Bong Joon-ho has offered (in various interviews) his thoughts on why the train has to keep moving

It's a literal prison

  • Stopping would allow people to get off

"This is true of all films, but especially Snowpiercer - the importance of space you can't emphasize enough, just the idea that these people are trapped inside this world. Of course Nam, a slight spoiler, he wants to live outside the train. He wants to escape the train. That's really essentially what this movie is about. The train is one big prison and the system that oppresses the people. That physical reality was very important and he didn't want to use CG for any of that. Of course the environment outside, a lot of that was CG. But inside he really wanted to capture the physicality of being in that space."

The setup is intended to benefit those up front

  • Stopping would allow people to gain access to the front of the train.

Q. What made that metaphor -- of the poor shoved into the back of the train and the privileged riding up front -- relevant and important to you?

A. The comic book came out 30 years ago, but the concept of capitalism driving the world is still relevant today -- it’s a very universal theme. Putting it in a train is kind of like Noah’s ark, but different from a boat or plane. A train is already divided into sections, and that feeling was very key. There’s a character called Nam (Song Kang-ho) who opens gates, and it’s only with great difficulty that they can move from section to section and open up a new world each time. The trick was to differentiate from one world to the next.


To add to John Smith's answer on the symbolic aspect of the movie, it can be noted that in the comics, the train actually can stop!

More precisely, there is a second train in the second and third tome. Larger and more comfortable than the first one, the autocratic central government keeps the power using the fear of a collision with the first train. The train regularly slows down as an emergency training to prepare the situation where the first train would be in sight. We learn at the end of the second volume that the first training was actually not a training and the government decided to harpoon the fisrt train, in order to get a second locomotive. The second train had to stop a few hour in order to load the loco. In the third volume, the train has to leave the tracks for a short time and to do so, it has to stop a couple of hours to prepare the train to move off-tracks.

For a review of the two first volumes of the comics. For French readers, this is a way better review.


If anything, it is explained that train produces water through the snow and ice picked up from the nose of the train. It would presumably need to keep moving to continue to produce water, also I believe it probably has something to do with producing power / electricity on the train


Why did the train need to keep moving?

From a physical sense, the reason it needed to keep moving was that the train itself, as explained in the videos the children watch, was intended to be self-sufficient; from that, one must surmise that the train derives some unexplained benefit by being constantly in motion; perhaps this motion is necessary to somehow enable other, lesser, train functions, such as maintaining the conditions (channeling the heat from friction, perhaps?) for the interior of the train.

Note that, again from the videos, the train was not built with global freezing in mind; it was built as a luxury experience. Considering your example of the ice-breaking generating water, we can guess that if rain existed (as it does not in the film since everything is ice), the train would gather the rain in the same way it gathers ice, to replenish water supplies.

If the train didn't keep moving, whatever unexplained benefit it might be deriving from moving would be lost, and based on exterior conditions, the train might be frozen in place, rendered incapable of moving to re-derive any lost benefits. This dangerous and unpredictable scenario cannot be chanced, lest all of what is left of humanity be put at risk (from whatever environmental conditions might endanger the train; eg. an avalanche), so the train must keep moving.


Could the train (which was built for a frivolous luxury experience before the climate disaster) have been quickly repurposed when the ice age began, to circle the globe following the slightly warmer summer season?

Other than that I can only assume that if the train stopped it might be difficult to get it going again, whereupon the winter season might catch up with the train and be so much more severe that even the train could not resist that level of cold?


Being a perpetual motion machine, stopping would halt momentum and disrupt equilibrium. The engine relies on the forward momentum of the train to keep running, and the forward momentum of the train depends upon the engine to keep moving forward. Take one away and the system fails and has to be restarted, presumably using some sort of fuel source that is either no longer available or in short supply. So it's best to never stop.


I would simply say that the train needs to move to keep the air warmer. As you know, in a car, the air conditioning works only if the car is on.

  • It only works if the electrical system is on. The engine doesn't even need to be working (except to recharge the battery) and the car certainly doesn't need to be moving to accomplish that. – user7812 Dec 29 '15 at 0:17
  • Actually the engine does need to be on in order to drive the compressor - the electricals only power the fan. – Nathan Dunn Jan 17 '16 at 13:07

Perhaps the train needed to keep moving in order to keep up with the summer weather, which would be much shorter due to the extreme global chill. This theory follows, that if the needed to continually remain in the warmer zone, it would imply that the other hemisphere would be much too cold for even the train to handle. Having said that however, the likelyhood of this being the reason the train is constantly in motion is rather slim, considering the iregular gobal train rout map design. The rout takes it in a perimeter vector along the coasts of all major land masses. It is still possible non the less. What do you think?

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