Can I please ask, pre covid, what happened to the locomotive off the Edinburgh lowlander. At Carstairs of course the two portions join and the Glasgow loco continues south. Did the Edinburgh locomotive wait there until 6am for the return lowlander sleeper?
I ask because having looked at what could happen with the Cally sleeper, you need 3 x 73s per night and 5 x 92s per night however I have looked at an alternative using 3 x 73s and only 4 x 92s. I don't think this is currently done since I can't find any paths in RTT for this to work logistically.
My alternative is make the loco off which does Edinburgh to Carstairs on the lowlander run back to Edinburgh to convey the highlander (and the 92 loco off the highlander which uncoupled at Edinburgh then going to Carstairs to haul the Edinburgh lowlander north to Edinburgh).
I also ask why does Cally need 3x 73s spare? A peak of 3 is needed so having 3 spare is quite extreme. Account for 3 operational and 1 in for repairs, you then need 1 spare and as has been mentioned above, it shows alternative locos can haul the sleeper so surely you should only need 2 spares rather than 3? Can anyone expand on that?
Given the subsidy that is given to the sleeper, having such a high requirement for the locomotives isn't good as they are paying to have them sat around half the day doing nothing.