I think that what Earl is saying is that since the 0503 is displaying a set of rear markers (indicating the rear of a train on the main track) and that it is with the 488, this must be a train
other than the scheduled passenger trains. They could also be doing some switching and the 0403 may be going on the end of the scheduled passenger train.....who knows?
The photo gives the impression that the locomotive and caboose are going somewhere (because of the markers) and this train is not a scheduled passenger train.
MDR