Type 4 Locomotives of British Rail

The six principal classes of diesel locomotive that once made up the 'Type 4' classification - the 40, 44, 45, 46, 47 and 50 - were the survivors of a wider group that can trace its origins to the British Transport Commission's Modernisation Plan of 1955. Designating a power output of between 2,000 and 3,000 hp, the type once contained representatives of several non-standard and one-off prototype ...