Bahnschutzpolizei (BSP) (Railway Protection Police) in Nazi Germany was made up of full-time and part-time police officers who were employees of the Reichsbahn (state railways).
It was not subordinated to Hauptamt Ordnungspolizei, only the Deutsche Reichsbahn.
[1] The BSP was a special police organization (Sonderpolizei) completely subordinated to the Deutsche Reichsbahn.
During World War II most of the BSP personnel were mobilized and used as a permanent railway security force in the occupied Eastern Europe.
[2] As a replacement within Germany, the SS-Bahnschutz, a railway security force under the SS was founded in 1944.