Many routes simply did not have the demand to economically justify locomotive-hauled passenger express trains, so railcars were seen as a viable alternative.

[1] Six in total were built in the NZR Hutt Workshops in 1938 and 1939, each with a semi-streamlined design featuring slanting ends.

The original silver body colour with a green stripe was inconspicuous and was soon replaced by plain red with grey or black roofs.

In September 1938 RM 30 covered the 321 km between Napier and Wellington in 4 hours and 36 minutes running time.

Today, RM 30 resides on the Silver Stream Railway in Wellington and is commonly used on running days.

RM 32 is now located at the Glenbrook Vintage Railway south of Auckland; the railcar moved there in 2001 after the proposed overhaul fell through and the Te Rapa loco depot was demolished, requiring it to find a new home.

The car attended the 2008 North Island Main Trunk centenary celebrations, but at the time was not mainline certified.

[12] As part of the mainline qualifications, RM 31 has been fitted with an events recorder, train radio, and ditch lights at either end.