High Quality Content by WIKIPEDIA articles! Pacer is the operational name of the British Rail Class 140, 141, 142, 143 and 144 diesel multiple unit railbuses, built between 1984 and 1987. Many Pacer railbuses are still in use today.The 'Pacer' series was a project by British Rail (BR) to create a train, with low running costs, for use on rural and suburban services. At the time, BR was under increasing financial pressure from the government including proposals to cut more rail lines. BR set a challenge to several companies to design a cheap, lightweight train similar to railbuses. Since then, 165 Pacer trains (totalling 340 carriages) have been built, with many of the oldest at nearly 25 years old remaining in service in 2009.