Four suburban 'Harris' trailer cars were converted to railmotor trailer use in 1984. They were to replace older trailer cars built from 1928.
One of the main areas of use was the Frankston to Stony Point run coupled to DRC_ railcars.
The class for the cars was given as MTH. They were numbered 101 - 104.
The cars were converted with self contained power supply; a motor generator under the floor supplied power. This allowed the car to be attached to any train as required. In some cases when the DRC railcar was unavailable, the trailers were attached to passenger locomotives for the service.
Conversions were: MTH 101 ex _BT_ 517, MTH 102 ex _T__ 679, MTH 103 ex BT 524, MTH 104 ex T 672.