All New Zealand railcars are classified as RM (Rail Motor), and this class derived their nomenclature from the name of the manufacturer, the Vulcan Foundry of Britain.

Six railcars of the Standard type were under construction at the Hutt Workshops but delays in deliveries of materials and equipment from England meant it was impracticable to build more cars in New Zealand.

Ten railcars were built, but only nine arrived in New Zealand as the ship carrying the tenth was sunk during World War II.

On trials on 25 October 1940, RM 50 achieved a speed of 125.5 km/h (78 mph) on a section of the Midland Line east of Springfield.

[7] From 7 September 1942, wartime petrol restrictions meant the Vulcans were put into service on the Stillwater–Westport Line between Greymouth and Westport (150 km or 93 miles), even though the line through the Buller Gorge technically wasn't finished and hadn't been handed over to the Railways Department from the Public Works Department.

[6] With double running (two cars coupled together) this meant four vehicles could be required for these services, which connected with Christchurch–Greymouth passenger express trains at Stillwater.

[7] Also due to the petrol restrictions, a service between Christchurch and Timaru was instituted[7] and the Hokitika run extended all the way to Ross.

After the war ended, the West Coast services continued to operate, but the Timaru run ceased.

[7] This allowed freed-up Vulcan railcars to provide daily Dunedin–Cromwell passenger services along the Otago Central Line (250 km or 155 miles) from 1 October 1956.

[11][12] By the end of the 1960s, road coaches could provide a similar service to the Vulcan and 88-seater railcars, at much lower cost.