WAGR P and Pr Classes

The WAGR P and Pr classes are two classes of 4-6-2 "Pacific" type steam locomotives designed for express passenger service on the Western Australian Government Railways 1067mm (3'6") narrow gauge mainline network. The initial designs were prepared by E.S. Race and together the two classes had a total build number of thirty-five locomotives, the P and Pr classes entering service in 1924 and 1938 respectively. Both classes were used on express passenger services, greatly improving the economy and speed of long-distance passenger travel in Western Australia, the results of which were most visible on the West Australian stage of the Trans-Australian Railway, the 'Westland Express'.

The need for more powerful locomotives in the 1920s resulted in the introduction of twenty-five P class locomotives which provided a significant improvement in power, speed and economy over previous WAGR locomotives, quickly proving to be a highly successful design. The Great Depression of the 1930s, coupled with the effects of The Great War, thwarted the WAGRs later expansion and acquisition plans resulting in many obsolete locomotives remaining in operation into this period. As a result ten new P class locomotives featuring detail improvements to boilers, valves and bogies were introduced in 1938, a year before the outbreak of the Second World War. The new locomotives became the first WAGR engines to be given names, each bearing that of a prominent West Australian river. These 'River class' locomotives were very successful and proved so invaluable to the operation of the wartime WAGR that eight P class locomotives were modified to their standard. All eighteen locomotives were officially classified as the 'Pr Class' in 1946.

The initial ten P class locomotives were built for the WAGR by the North British Locomotive Company in Glasgow while the remainder, including the new ten Pr class locomotives, were built locally by the WAGRs Midland Government Railway Workshops in Midland near Perth. One example of the P class (P 508) and one example of the Pr class (class leader Pr 521 Ashburton) are preserved in non-working order at the Australian Railway Historical Society's Rail Transport Museum in Bassendean, Perth.