In 1925, the South African Railways placed two American-built Class 16D locomotives with a 4-6-2 Pacific type wheel arrangement in passenger train service.

The engines introduced several features which were new to the SAR at the time, such as top feeds to the boiler, self-cleaning smokeboxes, Sellar's drifting valves, and grease lubrication to the coupled wheel axle boxes, crank pins and connecting rod big ends.

To compensate for the loss of tractive effort due to the larger diameter wheels, their operating boiler pressure was increased from 195 to 205 pounds per square inch (1,340 to 1,410 kilopascals) by an adjustment of the setting of their safety valves.

[2] In the Western Cape, wheatland fires caused by locomotives were a huge problem for farmers as well as for the SAR who had to pay out the claims.

[8][9][10][11] The introduction of these large engines, along with their Class 15C 4-8-2 Mountain type Big Bill siblings, resulted in a complete revision of traffic operation between Cape Town and Johannesburg.

860 made locomotive history by hauling the Union Limited, later to become the Blue Train, over a distance of 956 miles (1,539 kilometres) from Johannesburg to Cape Town in 29 hours.

On ordinary trains, up to six locomotives were often used with engine changes at Klerksdorp, Kimberley, De Aar, Beaufort West and Touws River.

[1][2][3] Upon the arrival of larger locomotives, the Class 16D was later transferred to Bloemfontein in the Orange Free State, from where they worked north to Johannesburg.

In 1939 they were relocated to Cape Town from where they hauled fast local commuter trains to Wellington and Malmesbury for the remainder of their careers.