In 1971, the DB commissioned the development of two prototypes of the series 614. These diesel multiple units, specifically designed for district and regional transport, were an evolution of the series 624/634 and featured a slightly tapered body shape to accommodate a so-called "track curve-dependent body control (GSt)." This gave the trainset its characteristic appearance. However, since the GSt ultimately proved ineffective, it was omitted in the 40 series vehicles delivered between 1973 and 1977, although the body shape remained. MAN produced the center cars for 25 units, while the Uerdingen wagon factory manufactured the driving cars, each equipped with either a 330 kW or later a 367 kW engine. The last 15 sets (from 1975) were completely manufactured by MAN. Although the trainsets were designed as three-part units (204 seats in second class and 2 x 12 seats in first class), they were capable of multiple traction and occasionally operated as four-part units with an additional center car, especially in the early days. However, multiple traction was quite rare, and in later years, it almost ceased to exist. The first 25 units were assigned to the Bw Nürnberg, from where the trainsets were deployed on all non-electrified routes in Franconia and the Upper Palatinate. The typical color scheme at that time was the "Pop" livery of blood orange and pebble gray. The last 15 trains, now in the color scheme of ocean blue and ivory, were stationed at Bw Braunschweig, from where they operated on routes to Paderborn, Göttingen, Münster, or Bielefeld. They could also be observed on the Heidebahn from Buchholz via Soltau to Hanover towards the end of their service. Most vehicles were later painted in mint turquoise and light gray, and by the end, almost exclusively in traffic red. As part of a partial modernization, several units received a more powerful engine (448 kW).