A year ago, I took a picture of an early articulated split-level coach in the collection of the DB Museum in Nürnberg. The descriptions on the museum grounds had some subtleties not yet in my German vocabulary.
The coach dates from the middle 1930s. It was built for the Lübeck-Büchener Eisenbahn, a private railroad that became part of the state railroad in 1938. (More about Lübeck-Büchener Eisenbahn, two sites auf Deutsch.) What I couldn't figure out there, but have since learned, is that it was fitted with remote controls in order for the engineer to be able to control the speed of a steam locomotive pushing on the hind end. The remote control of a steam locomotive from the far end of a coach in order to obviate run-around moves was established railroad practice, in Britain these were called motor-fitted trains, and sometimes the steam locomotive would be placed between two such coaches, the linkage being too imprecise to be set up with anything other than the locomotive adjacent to the coach.
But the Germans modified some 2-6-0 tank locomotives into 2-4-2 tank locomotives (although the 2-4-2 is not the most stable wheel arrangement, having a steering axle at each end is helpful on a locomotive that runs in reverse half the time) and put a streamlined casing on it.
The railroad's fans have set up a Facebook page, from whence I retrieved this image of a train, here in pull mode, crossing an Autobahn. Looks a little like U.S. 41 in the Chicago area. (Nose around on the page and you'll see an image of two such coaches, with a diesel marshalled in the middle.) That allowed the railroad, in its publicity, to brag on their commuter streamliners.
That's at the Illinois Railway Museum, a somewhat easier trip than to Nürnberg. It's simpler to run the control lines for a diesel through multiple coaches. The museum is able to roll out a three-car rake (all seats required for Thomas weekends) whilst Metra run up to twelve car trains at rush hour. Meanwhile, the Germans have created up to quint-articulated split-level coaches for their regional trains.