As Melbourne was never constrained by tight curves or stations in tunnels like New South Wales, the railways in Victoria were able to increase train capacity by lengthening cars, extending platforms and increasing the number of cars on trains.
In 1990, the rail administration decided to purchase a four car 'Tangara' set from a builder in New South Wales. The set in service became known as the '4D' set as the carbody was wider and there some differences for running on the Melbourne system.The set wass built by Goninan in December 1991 and transferred to Victoria. At the time, this set was to be a precursor for a further contract of 19 other sets.
The four car set was an unusual configuration in that cab controls and pantograph were fitted to the trailer cars and traction equipment was located on the motor cars.
The two M cars were numbered 5000 and 5002 and entered service during March 1992.
The MET modified the electrical equipment to enable compatability with the 'Comeng' sets in service. For while, the 4D could be seen in service coupled to other three car Comeng sets. To accomplish this, braking and acceleration had to be modified.
In service the set ( _T__-M-M-T ) has run as a four car train mainly on the Ringwood - Melbourne line. It had been planned to run this train on most lines inluding Werribee, Pakenham and Belgrave lines. However with derailment problems in NSW and the risk of level crossing accidents has caused the 4D set to be constrained to limited service on the Lilydale/Blackburn services. Sydney has a limited number of level crossings on suburban lines whilst in the Melbourne metro area, they are quite prolific.