They were built by General Motors Diesel (GMD) of Canada as a narrow-gauge version of the EMD G8 model, with seventeen locomotives constructed.

Upon the introduction of the computerised Traffic Monitoring System (TMS) in 1979 the class was renumbered and the designation capitalised.

The units being rebuilt to DBR received a new TMS number in the 12XX range when they entered the rebuilding cycle.

[6][7] The DB class was employed primarily freight duties, though they did also see occasional service hauling passenger trains.

The two locomotives, DBRs 1199 and 1254 are operated in a top and tail configuration with the five car SX carriages set and wore the full MAXX Blue livery.

[11] For many years two DBR class locomotives formed the basis of a banker set out of Wellington, primarily assisting trains between Wellington and Paekakariki but also performing multiple other jobs including the Hutt Workshops shunt, work trains around the region and any unusual movements.

In the early 2000s DBR1199 suffered a failure and was withdrawn from service and laid up, replaced on the banker set by DBR1267.

DBR1199 was later sent to Hillside for repair and use on the Auckland SX set commuter trains, by which time the pairing of DBRs 1200 and 1267 had become known simply as "The Twins".

The locomotives were delivered in the same overall deep red livery as the DA class, with the same white stripes along the sides and "wings" on the ends.

This livery was worn by many of the original DBs until their retirement, while the DBRs were returned to service in the International Orange or "Fruit Salad" scheme (red and grey with yellow safety ends) being applied to most NZR locomotive classes at the time.

[13][14] DBR1199 was reinstated a year later for suburban trains in Auckland,[10][15] and 1239 and 1241 were scrapped at Hutt Workshops in February 2008.

[22] In June 2017, KiwiRail issued a Request for Quotation (RFQ) via the Government Electronic Tendering Service (GETS).