Wikipedia
Kleinbahn
The term Kleinbahn (literally 'small railway', plural: Kleinbahnen) was a light railway concept used especially in Prussia for a railway line that "on account of its low importance for general railway transport" had less strict requirements placed on its construction and operation that main lines (Hauptbahnen) or secondary lines ( Nebenbahnen i.e. normal branch lines). Even public railway lines built for constructional or industrial purposes were counted as Kleinbahnen.