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.
VR Class Dr12
When it was introduced, the Dr12 gave drivers a new experience of comfort and forward visibility compared to steam locomotives, but compared to the newer VR Class Dr13, the Dr12 had a heavy axle load and slow acceleration with a top speed of only 120 km/h. The reason for this was that the locomotive turned out to be underpowered. The problem of the top speed was corrected in the last 10 locomotives by changing the transmission in such a way that the technical top speed was increased to 140 km/h, but this feature was never used. As a result, the entire locomotive series had a maximum permissible speed restricted to 120 km/h. However, due to the high axle weight, the Dr12 had good adhesion properties and it was considered to be a reliable and robust locomotive. It was well-suited to heavy trains with relatively low speed requirements.