Milwaukee Road class F7
The F7s are major contenders for the fastest steam locomotives ever built, as they ran at over daily. One run in January 1941 recorded by a reporter for "Trains" magazine saw achieved twice—in the midst of a heavy snowstorm. Baron Gérard Vuillet, a French railroading expert, once recorded a run between Chicago and Milwaukee where the locomotive reached and sustained an average for . However, the British locomotive LNER Class A4 4468 "Mallard" is officially accepted to be the world's fastest, with a run recorded at but authenticated at 126 mph in 1938.
SJ D
When the passenger locomotives were given more powerful motors, they were designated Dk. They had a maximum speed of 100 km/h. This is the last series of locomotives that was built new, all later types have been rebuilt, except the one-off experimental subtype Dr. The last Dk loco was built in 1943 and concluded eighteen years of D production. When the production of Da-locos started in 1953, the Dks were rebuilt to the same engine, and received the designation Du. The last use of Dk was in 1975. In total 117 have had the Dk designation, of which 73 were built as Dk.