Working out how to get a propulsion system to drive your trailer is one of those ideas which people think of, but the technical issues can be difficult to surmount. SAF seem to have got this one up in the European market. It has been specially developed for dump trailers and walking floor vehicles operating in the area of construction sites or landfills. The hydraulically driven motor is said to be long-lasting and low maintenance, thereby ensuring the new trailer axle has an exceptionally long service life.
Of course powered trailers are nothing new and Australia has a tradition of some pretty big stuff powering trailers, especially in the mining industry. Note, the Cummins engine is slung under trailer number three:
The same principle has been used underground, in this example the prime mover and first trailer are using Detroit Diesel Series 60 engines:
Here is a much more basic example on a palm oil plantation: