British Rail Class 144 Pacer

The BR Class 144 Pacer was the final and most refined variant of the Pacer family, with twenty-three sets built between 1986 and 1987 by BREL Derby working with Walter Alexander Coachbuilders. The Class 144 combined the Walter Alexander bus-derived body (as used on the Class 143) with an improved underframe design and a more powerful Cummins engine specification, addressing some of the criticisms that had been levelled at the earlier Pacer variants in terms of performance and ride quality.

The sets were built primarily for Yorkshire services, allocated to depots in the Leeds and Sheffield areas and intended to work the busy cross-Pennine secondary and local services that had previously been operated by ageing first-generation DMUs. The Walter Alexander body gave a somewhat more substantial feel than the Class 142's Leyland National body, and the improved underframe reduced — though did not eliminate — the rough riding that was the Pacer family's most consistent criticism.

The Class 144s worked Yorkshire local services for over thirty years, becoming closely associated with the Leeds–Sheffield and Leeds–Harrogate corridors under Regional Railways and subsequently Northern Rail. Their withdrawal in 2019 was accompanied by considerable publicity as the last Pacers in service on the national network, marking the end of the bus-body-on-railway-underframe experiment that had characterised much of BR's rural DMU provision in the 1980s. Several examples have been preserved.