Right now, the "Koutetsujou" (Dammit, I really wish they translated this as Steel Castle/Fortress, because that's how the kanji reads and it's much cooler than alien language to English speakers) is a really cool setting. It reminds me of the movie Snowpiercer, where everyone has to survive inside a train. I also like the term hayashiro (fast castle) for trains in general. It really fits the setting and the purpose of the vehicles in light of the zombie apocalypse.

Their train is pretty much ok though. With two Kabaneris guarding them, zombie mobs should be no problem. The problem is when elite zombies show up, and they will. They always do in zombie stories.