First production pacer class introduced in 1984.

The British Rail Class 141 was the first production model of the Pacer diesel multiple unit (DMU) railbus.

During the 1980s, British Rail (BR) was interested in replacing its first-generation diesel multiple units, particularly in the use of railbuses to service its lightly used branch lines. It was decided to develop such a vehicle with a high level of commonality with the widely used Leyland National bus, leading to its modular design serving as the basis for the design.