I find it interesting because it reveals a side of humanity that puts into question highest boast of civility and order amidst chaos. It makes us put ourselves in the shoes of the characters and ask the same question of 'what will I do given the same circumstances?'
Zombie movies function as a mirror to our collective values and pretenses on matter of survival and being human. It dares to put us in the middle of the tension between living to fight another day in an eternity of living dead; asking us whether it is actually us the survivors who are the real walking dead for we are no longer different from the zombies who are driven by the primal urge to press on living at the expense of others lives.
It is on this theme of the zombie movie genre that I find Yeon Sang-ho's Train to Busan a welcomed contribution to themes advanced by the zombie genre. I find it special because it saliently functions as a Marxist social commentary to the conventions of class relations, that is more relatable than George Romero's take on the idea in his movie Land of the Dead.
Marxist class categories in the movie characters
The Petite Bourgoise - Seok-Woo can be looked at as representative of the petite bourgoise can change and learn from the masses in the midst of struggle. His fate as part of the company that created the virus also serves as a cautionary tale about the demands of justice to be served even to those who have the best intentions as reasons for perverting it.
Insights and afterthoughts
The film shows the youth's capacity to go beyond themselves, and to discern based on emotion beyond reason is sometimes helpful as seen in the way Jin-hee and Young-gook the sole survivors of the baseball team responded to the outbreak, which in a way reminds me of the the generation of youth that went out to organize the anti-Marcos dictatorship in the 70s.
With regards to technology (biotech and/or nukes, which are hinted as possible causes of the zombie outbreak) are technologies that must be looked at from the lens of precaution (see precautionary principle) because the nobility of intention for its use must not supercede the science where the danger outweighs the benefits. After all, the road to hell is paved with good intentions and our best ideals will only be judged on the merits of how far we lived up to them.
It also paints a familiar portrait of the government, as a force that imputes blame on the crisis to peoples' movements, as seen with the outbreak being blamed as social unrest borne out of workers' strikes. A government that saves face that does not ones' deserve obedience.
A subtle moral of the story: unquestioning obedience to the ruling class renders one to become cannon fodder and turns us into the vicious executioner of the ruling class' self-interest as with the case of the train conductor and the few survivors who did Yong-Suk's bidding.
The movie ends with a theme of reversal where the survival of the pregnant Seong-kyeong and the child Su-an as a triumph of the vulnerable over a survival of the fittest social order that came out of the zombie outbreak.