From The Great War (1914-1918) Forum.
A Divisional Train was a key link in the resupply chain. Pack trains (rail) originated at the Channel ports and went forward to the railhead. From there, the Divisional Supply Column (mechanical) carried the stores forward to the Replenishment Point where they were handed over to the Divisional Train (horse) that carried them forward to where they were turned over to the units at the Delivery Point (DP). In practice, the process was modified based on local circumstances.
Railhead
the point at which material and personnel are transferred from rail to another conveyance.
Edit:
https://www.longlongtrail.co.uk/army...isional-train/