A quick look at the Korea Urban Transport thread at SSC: Subways turned out this photo.

Photography by ds8789 of Flickr
See those cables running on the edge of the platform?

Photography by ds8789 of Flickr
See them again? Those cables act as a platform door. So in other words, if SkyTrain needs platform doors, we could install cables/glasses that move vertically upwards and we wouldn't have to figure out door location issues with the MK I and MK II vehicles.