The SBB Bm 4/4 is a heavy shunting locomotive still frequently used by the Swiss Federal Railways SBB. They will be replaced by the SBB Am 843. The standard load is 365 tons at 15 km / h

The engine should be able to come as a light mainline used to allow complete detachment of the Steam Engine. There was also the part of the Federal Department of Economic Affairs (DEA ) and the Military Department (EMD ) an interest to expand the catenary and independent traction reserve, so the DEA acquired a 60 % interest in the procurement of 16 locomotives and the EMD of six locomotives.