The 400/500 class rail motors are diesel trains built by New South Wales Government Railways primarily for use on regional lines throughout NSW.
The trains have since been phased out following a rationalisation of country branch line rail services in November 1983. The 400 Class power cars were built in 1938 at the Eveleigh Carriage Workshops, while the 500 Class trailer cars were built by Ritchie Brothers at Auburn.
The 400 Class power cars followed the same general lines as the Silver City Comet powers vans, although they were slightly shorter in length at 15.55 metres (51 ft 0 in). They were fitted with two underfloor 150 horsepower (110 kW) Leyland Diesel in-line six-cylinder, petrol engines coupled to Leyland Lysholm-Smith hydraulic transmissions.
402 was modified in 1972 with the installation of a compartment seating eight First Class passengers and a toilet at the opposite end to the main passenger compartment and coded HPC. It was planned to extend this modification to 401 and 403 but with the decline in passenger numbers, it was considered too expensive to be repeated. The others simply had four seats in the main compartment allocated to First Class.
402 was taken into Eveleigh Workshops in 1970 and emerged with a small first class compartment at the No.1 End seating 8 passengers. A toilet was also located in this section. The sliding luggage compartment door was removed and replaced by a pair of standard swing doors (large and small) and the luggage rating reduced to 4 tons. Dual sealed beam headlights were also fitted at this time.
The three surviving 400 class units have been preserved in heritage railway collections. HPC 402 now belongs to the Rail Motor Society at Paterson, NSW, and is the only unit remaining in operational condition. HPC 401 and HPC 403 reside in the collection of the Dorrigo Steam Railway and Museum at Dorrigo, NSW.