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.
Read more about Kleinbahn: Origin and Use, Construction and Operation, Today, Model Railway, List of Kleinbahnen, See Also