When it became clear that the first generation DMUs had reached the end of their service life and that the development of a full-fledged successor would take a long time, the Pacer was developed as a cheap temporary solution. The body of the Leyland National bus was used and placed on a two-axle underframe intended for a high-speed freight car. These two- or three-car vehicles were designed for a maximum service life of 20 years. Since the Sprinters could not replace them, almost all Pacers were still in use in 2015. From the passengers they got the nickname “Nodding Donkeys”, as they had very uncomfortable suspension characteristics and a high noise level. In 2019 and 2020, almost all were phased out, mainly due to new accessibility requirements. In June 2021, the last Transport for Wales vehicles ran for the last time.