You know how Wikipedia is; you click on one thing, then another, then another, and you find yourself reading about something that has nothing to do with what you originally looked up (case in point, Nora the Piano Playing Cat to Zillertal Railway).
Anyway, I found this picture and clicked on it to marvel at the European buffer and chain coupling system, when I realized that this car is on a car. http://en.wikipedia.org/wiki/File:Binder2.JPG . Unlike the train-on-train that was researched for 1067mm to 1435mm operation in the Tsugaru Strait tunnel, this is apparently to operate standard gauge on narrow gauge, only 760mm http://en.wikipedia.org/wiki/Zillertalbahn . Wikipedia calls these things transporter wagons: http://en.wikipedia.org/wiki/Transporter_wagon