Romanisation is done in the McCune-Reischauer system that is generally used in academic writing about Korea, especially North Korea and pre-1945 Korea; I didn't use the Revised Romanisation in part because - since it was developed specifically by a department of the South Korean government - it seems patently inappropriate to an NK-related application, but mostly because I find it aesthetically unpleasant and ill-suited to the job of representing the sounds of Korean in an effective way... but I won't go further on that.
Lastly a little disclaimer - none of this is to imply any sort of support of the DPRK government or its policies... I've just been fascinatedly following it for over two decades now, and I'm just a bit obsessed with their trains...
PS: Thanks Alberth!