The 4D was a prototype double deck electric multiple unit built for the Public Transport Corporation in Victoria, Australia, for operation on the Melbourne railway system.

"[3] Depending on sources, the intention was for this train to be the demonstration unit for a future order of either 20 or 50 extra sets, had the tests been successful.

[5][6] After being bogie exchanged, it was transferred to Jolimont Workshops on 18 December of the same year, for an inspection and final fit out.

[8] In addition, the individual carriages were narrower and shorter in both length and width against their predecessors, to fit the Melbourne loading gauge.

[4] It was manufactured from stainless steel and was fitted with air-conditioning, tinted windows, and inter-car doors, allowing passengers to access all carriages of the train.

Much of the equipment matched Sydney's Tangara fleet, from the traction motors (8x MB 3303B) down to small fittings like console buttons.

[7] As part of the trial, the Belgrave and Lilydale lines were selected as main testing grounds for the unit and necessary works were performed to accommodate the train's somewhat unconventional dimensions.

[4] The overhead wire to Belgrave and Lilydale was also altered, including the power feeds, and platforms were cut back where required.

It departed Flinders Street in the morning, running to Parliament station to collect the Minister for Transport and the awaiting media, before proceeding to Ringwood.

Throughout the remainder of the day, it conducted tours around the City Loop for Public Transport Corporation staff and their family members.

[10][11][4] Ownership of the 4D was transferred back to the Victorian Government's Department of Infrastructure, and the set was moved under its own power to Newport Workshops in December 2002, for long-term storage.