The Bm 4/4 is a class of heavy dieselshuntinglocomotives built for Swiss Federal Railways. 46 examples were built between 1960 and 1970, numbered 18401 to 18446, Starting in 2006, the class was slowly being replaced by new Vossloh-built locomotives. The last SBB example was withdrawn in 2024 but a few are in use with private operators