Engine, engine number 9!
And a right hand drive, too.
More photos from the battle, along with another of the ammo hauler:
I Should be a right hand drive, as these are British troops.
Photo is Crewe tractor No. 39 and trolleys of shells at a TT (trench tramway) transfer point in the Ypres salient, August 1917. The "Crewe Ford Tractor" was manufactured by the London & North Western Railway, Crewe Works. using a Ford Model T car chassis. 132 were built. They were "convertible" for both road and rail use. While not extremely successful they were useful at a time when a quick and inexpensive form of motive power was needed. A photo of the vehicle in road form: