Sydney was renowned among the Aussie fans as having the largest work car fleet in Oz. Of those, the “U” Ballast motors were the most prolific and were a “jack of all trades”, having towed cars (and flat trailers) to carrying sand to the various depots and hauling ballast and all other stuff involved in track relays. Sadly, in some cases (North Sydney for example) they would be the last car to traverse a line as it was being lifted.
Tramworks, has produced a model of the U4 type. The model is intended to be motorised using Black Beetle Drives from Steam Era and suitable working trolley poles. Qcar Company is a good source. I have not included dummy printed bogies or poles to keep the printing costs and kit price as low as possible making this a perfect introductory model to those new to the hobby.