Erdbahn

Erdbahn, literally "earth railway" in German, refers to a type of railway construction in which the track bed is formed primarily from natural ground or is only lightly surfaced with ballast. In historical German-language sources the term is used to distinguish this approach from ballasted tracks (Schotterbahn), where the rails rest on a thick layer of crushed stone. The designation is mainly historical and is most often associated with early or rural lines.

Historically, Erdbahnen appeared in the emergence of rail transportation when construction costs had to be kept low and soil conditions allowed stable subgrades. They were typically used on lines with light traffic and moderate speed, and occasionally on temporary or industrial lines. Over time, many Erdbahnen were upgraded to ballast tracks to improve stability, durability, and speed performance.

Construction and operation characteristics center on the reliance on the natural subgrade. The rails are usually fastened to timber or simple sleepers and laid directly on or just above compacted earth, sometimes with a shallow ballast layer. Drainage, frost heave, and soil settlement critically influence track geometry. The lack of substantial ballast reduces vertical stability and makes maintenance more frequent; curves and grades are therefore more limited compared with ballasted constructions.

Today the term is largely historical. Modern railway practice favors ballast or other engineered underlayers (such as concrete slab tracks) for longevity and performance. Variants of unballasted or lightly built track exist in some special-case applications, but Erdbahn as a standard category is rarely used in contemporary networks.