The three air-conditioned and sound-proofed 723-kW[1] 96-seater diesel-electric twin-set railcars were built by Kawasaki under contract with Nissho Iwai of Japan.

[3] New Zealand Railways (NZR) classified the railcars as RM (Rail Motor),[nb 1] the same as other railcars, using the Silver Ferns (a national symbol of New Zealand) because of their exterior was made of corrugated stainless steel, like the premier night sleeper train that also ran on the Wellington-Auckland (North Island Main Trunk) route, the Silver Star.

[8][9][10] Intermediate stops were at Palmerston North, Marton, Taihape, Waiouru, Ohakune, National Park, Taumarunui, Te Kuiti, Hamilton and Papakura.

[11] Under trade by Nissho Iwai, the Silver Ferns were built by Kawasaki and Toshiba and introduced in 1972 to replace older but refurbished Blue Streak railcars on the route.

[7] The success of the Blue Streaks had ensured there was a business case for NZR to purchase the three Silver Fern railcars.

The Silver Fern railcars would then be reallocated to the South Island to run the Picton-Christchurch service.

[16] The services were operated by Veolia Auckland as part of its contract with ARTA, with the units leased from Tranz Scenic, later KiwiRail.

In 2010, a major refurbishment of the units commenced in Wellington to extend services, with the program completed by mid-2011.

Following a refurbishment of RM30, Tranz Scenic operated various excursion services under the Explore by Rail brand.

This work included the stripping of the interior in the passenger saloons, allowing corrosion repairs to be carried out.

[23] On 18 August 1981, half of the first and second sets derailed and rolled north of Waiouru when the northbound service was descending curves.

Passengers reported that the railcar had been travelling quickly over this section of the journey and the speed around curves just before the derailment had been concerning.