I can only answer re: the tipper wagon & drag from my experience of living and driving in Aus.
The extra long ‘tow bar’ is to allow the driver to tip the trailer and then reverse it so that it comes down the side of and parallel to, the main unit, so that he can then tip the unit in the same spot. You can literally reach out of the window and touch the tailgate of the trailer when doing this. In Aus they are called truck and dogs and i’m assuming they are similar, if not the same thing that they use over the pond.