 Although originally designed as a goods locomotive, their maximum permissible speed was raised in the 1950s from 45 to 50 mph (72 to 80 km/h) for branchline passenger service, further increasing their versatility.The success of the K class was such that even in 1953, with dieselisation already underway on Victorian Railways, the basic design of the K class was updated into the J class 2-8-0, the final class of steam locomotives to be introduced to the Victorian Railways.During the mid-1930s, the original batch of ten K class locomotives were equipped with VR's 'Modified Front End' for improved drafting and reduced cylinder back pressure.