Checking on the figures, 550 m corresponds to 14 wagons, which are twin articulateds, so the range seems to be from 18 complete semi-trailer truck units (with 18 half-cars carrying the semi-trailers and 9 the road trucks) to 28 unaccompanied semi-trailers.

in half an hour

That's the unload-plus-reload time.

_{*Lunatic*, n.
One whose delusions are out of fashion.}