I've seen a couple of these in Germany. Basically, this type of truck looks like a tractor with a "soft-sided" trailer. In short, the trailer has a rectangular frame with very heavy tarps on each side. Boxed cargo fits in, they secure the tarps, and away they go.
I've seen some pretty incredible ads put on these while motoring down the autobahn. I thought it was a hard-sided box trailer at first until I saw the sides move just a little in the wind at road speed. They really can crank them down until they're really taut, and you can't easily see the tensioning ratchets a lot of times.
I think the most extravagent illustration I saw on one of these trucks was an ad for orange juice!
Why the soft sides? So you can back the trailer into a bay and unload from three sides. Makes it easy to get cargo that is in the middle of the trailer, too, while keeping the other stuff on board for dropoff at a later location. Some nations in the EU have OTR drivers pay taxes based on number of axles, not just GWT, so if the load doesn't merit three axles, they pull a set up (like some dump trucks in the US can).
v/r, N-A