Originally Posted by jiejie

D trains also require real ID same as C and G. Just those 3 types so far though, remember "CDG." You'll need to find name/ID/passport of a fourth person to book an empty berth on these trains. As reported on other thread(s), nobody official seems to be inspecting ID's when boarding or riding the actual journey. So the fact that no fourth person actually shows up is likely to go un-noticed...or as I said above, use the "in the bathroom or dining car" trick if it does.

Or, get sleeper tickets for the Z, T, or K trains which are slower but which require no ID. Or fly and dispense with train worries.