I've been trying to figure out the categories for class numbers and could use a little help!
As far as I know (with examples):
Class 1xx: DMU (150, 153, 158)
Class 2xx: DEMU (221, 222, 230)
Class 3xx: EMU, OHLE (313, 315, 317)
Class 4xx: EMU, 3rd Rail (442, 444, 450)
Class 6xx: Hydrogen (600...