4D Train
The 4D was a prototype double deck electric multiple unit built for the Public Transport Corporation, Victoria, for operation on the Melbourne railway system. It remains the only double deck train ever to have run in Melbourne.
Design
Built by A Goninan & Co, Broadmeadow it was delivered by rail in December 1991.
The train's design was based on the Tangara train being built by A Goninan & Co for CityRail in Sydney, however it was similar only in terms of interior and exterior bodywork; the train's electrical system was much closer to that of the Comeng sets. The design was further modified for use on Melbourne's broad gauge track, and its control system was designed specifically to allow in-service coupling and operation with Comeng sets.
It was manufactured from stainless steel, fitted with air-conditioning, tinted windows, and inter-car doors allowing passengers to access all carriages of the train. It had a total passenger capacity of 974 passengers: 346 seated and 628 standing.
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. It was known that the train was physically too large for the Jolimont tunnel between Jolimont and West Richmond railway stations on the Hurstbridge and Epping lines. Given that the train was a demonstrator, it was likely that production designs or future infrastructure plans would have dealt with this.