Feldbahn

A Feldbahn, or Lorenbahn, is the German term for a narrow-gauge field railway, usually not open to the public, which in its simplest form provides for the transportation of agricultural, forestry and industrial raw materials such as wood, peat, stone, earth and sand. Such goods are often transported in tipper wagons, known in German as Loren, hence such a railway is also referred to as a Lorenbahn.

Source: Wikipedia