The introduction of diesel locomotives had revolutionised the main arterial railways of New South Wales. However, the regions had yet to see the benefits from their introduction. Due to the light maximum axle loads permitted on the branch lines that crisscrossed the state, many regional towns and centres had not seen the benefits of more powerful steam locomotives such as the 36 or 38 class.

In fact, most were still being serviced by a fleet of steam locomotives approaching upwards of 70 years of service, resulting in spiralling costs for maintenance and operation. To curb the losses, the NSW Railways ordered a test batch of smaller diesel locomotives designed for branchline working.

Significantly smaller and lighter than the mainline diesels that were introduced before them, the 48 Class at last provided relief to the regions desperate for new locomotive power. They were an immediate success, with successive orders bolstering the Class to an impressive 165 members.

Although not capable of the considerable output of their larger cousins, the locomotives were extremely versatile. Working regular services along both major main lines and into the regions, the 48 Class quickly found themselves on a range of services, from passenger trains along the South Coast Line to fast interstate freight trains.