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.
Steam locomotive
In 1998, in his book "The Red Devil and Other Tales from the Age of Steam", David Wardale put forward the concept of a high-speed high-efficiency "Super Class 5 4-6-0" locomotive for future steam haulage of tour trains on British main lines. The idea was formalised in 2001 by the formation of 5AT Project dedicated to developing and building the 5AT Advanced Technology Steam Locomotive, but it never received any major railway backing.