Pacer (British Rail)

Pacer was the operational name of the British Rail Classes 140, 141, 142, 143 and 144 diesel multiple unit railbuses, built between 1980 and 1987. They were inexpensively developed using a passenger body based on the Leyland National bus on top of a chassis based on the HSFV1 research vehicle. The railbuses were intended as a short-term solution to a shortage of rolling stock, with a lifespan of no more than 20 years. As modernised replacements were lacking, the Pacer fleet remained in service on some lines until 2021 37 years after their introduction in 1984.

All Pacer trains were scheduled to be retired by the end of 2019 as the Rail Vehicle Accessibility Regulations require that all public passenger trains must be accessible to disabled people by 2020 however the Pacer units were given dispensation until the end of 2020. Only one Pacer (the modernised 144e) met this requirement, and the remainder were therefore planned to be withdrawn by that date. Furthermore, a decision in 2015 by the Transport Secretary required that such railbuses be removed from service by 2020 for the then-new Northern franchise, stating that the "continued use of these uncomfortable and low-quality vehicles is not compatible with our vision for economic growth and prosperity in the north".

At the start of 2020, 138 Pacer units of classes 142, 143 and 144 were either still in service or storage with three National Rail operators: Arriva Rail North, Great Western Railway and KeolisAmey Wales. After the 144s were withdrawn from the Northern franchise, Northern Trains retired its last Pacer unit, a 142, on 27 November 2020, with Great Western Railway following with its last 143 in December 2020. KeolisAmey Wales withdrew only its 142s in late 2020, passing its 143s to Transport for Wales Rail who finally phased them out in May/June 2021.

Features

The Pacer series were built with low construction and running costs in mind, and so all of the Pacer units use:
* A lightweight modified bus body and other bus components, such as seating, with a reinforced driver's cab area to comply with crashworthiness standards.
* A long-wheelbase four-wheel freight-wagon-inspired underframe, rather than the conventional arrangement of two four-wheeled bogies. This arrangement has been criticised for rough-riding, and causing loud noise and excessive wear to the wheels and track on tight curves.

Background

By the beginning of the 1980s, British Rail (BR) operated a large fleet of first generation DMUs, such as the Class 101, which had been constructed in the 1950s and 1960s to various designs. While formulating its long-term strategy for this sector of its operations, British Rail planners recognised that there would be considerable costs incurred by undertaking refurbishment programmes necessary for the continued use of these ageing multiple units, particularly due to the necessity of handling and removing hazardous materials such as asbestos. In light of the high costs involved in retention, planners examined the prospects for the development and introduction of a new generation of DMUs to succeed the first generation.

In the concept stage, two separate approaches were devised, one involving a so-called ''railbus'' that prioritised the minimisation of both initial (procurement) and ongoing (maintenance & operational) costs, while the second was a more substantial DMU that could deliver performance superior to the existing fleet, especially on long-distance services. While the more ambitious latter requirement would ultimately lead to the development of the British Rail Class 151 and the wider Sprinter family of DMUs, BR officials recognised that a cheaper unit was desirable for service on the smaller branch lines that would not be unduly impacted by lower performance specs or a high density configuration. As such, work to progress both approaches was undertaken by BR's research department during the early 1980s.

During this period, a number of prototypes were constructed to explore different designs and approaches for implementing the railbus concept. The initial prototype, known as LEV 1, was a joint project by the British Rail Research Division and Leyland Motors and used a bus body mounted on modified freight vehicle underframe ( HSFV1). A subsequent test vehicle, a single two-car unit, designated as the Class 140, was constructed between 1979 and 1981. The principal difference between the Class 140 and the preceding R3 concept was the incorporation of the underframe structure into the body above, thus making the latter a load-bearing structure. Other changes included the strengthening of the cant rail area and the use of standard BR multiple unit ends, enabling compliance with full Union Internationale des Chemins de fer (UIC) end load specifications for multiple units. Internally, a mixture of standard railway multiple unit seating and bus seating was installed. The resulting railbus was relatively lightweight, as had been desired by BR's concept.

The Pacers had originally been intended as a low-cost stopgap solution to the rolling stock shortage, with a maximum lifespan of 20 years. A total of 165 Pacer trains (totalling 340 carriages) were built for BR. By 2015, the majority of these remained in operation with various private train operating companies, despite the type being in excess of 30 years old. Outside of the UK, Pacer demonstrator units toured various nations, including the U.S., Northern Ireland, Belgium, Sweden, Thailand, Malaysia and Indonesia, without producing significant sales. However, Iran purchased redundant Class 141 units, for use on suburban lines around Tehran until 2005.

Class 140

The Pacer series was the result of an experiment to assess the viability of using bus parts to create a diesel multiple unit. The two-car Class 140 was a prototype vehicle that was built in 1980 at British Rail Engineering Limited (BREL)'s Derby Litchurch Lane Works. This prototype was introduced with much fanfare during June 1981. During its trial period, the Class 140 toured various lines across the UK. It later functioned as a demonstration unit for the incoming fleet based on the type, the Class 141. By 1985, the unit was in use as a driver training vehicle. From September 1986, the sole Class 140 was allocated to Neville Hill.

Initial testing with the Class 140 uncovered several issues, such as difficulty detecting the type via track circuits, this was reliably resolved by swapping the material of the brake blocks from a composite to iron. Two less easily addressable drawbacks were the high level of noise generated during transit, particularly on older jointed rails, which was a consequence of the railbus's direct connection between the underframe and suspension with the body that transmitted impact forces across the body. It was also observed that the inclusion of strengthening members in the mass-produced bus body added significantly to the overall production cost, which eliminated much of the cost advantage that was the primarily goal of the type. The original traction power train of the Class 140 consisted of a Leyland TL11 200 HP engine, a Self-Changing Gears mechanical automatic gearbox and a Gmeinder final drive unit on each car driving only a single axle. This propulsion arrangement was in part taken from the Leyland National bus. The controller for the automatic transmission was observed by BR engineers to the cause of numerous operating failures and other reliability issues; this was allegedly due to defective relay logic and poor earthing.

Class 141

The Class 140 was viewed to be an overall success, and thus BR issued an order for an initial production model, designated Class 141, to British Leyland during 1984 with production commencing thereafter. During its early years of service, the Class 141 experienced numerous issues, particularly with the transmission and ride quality; work undertaken at BR's direction resulted in the quick development of numerous improvements to at least partially address these shortcomings. When it came to ordering more railbuses, however, it was decided that instead of placing these follow-on orders for further Class 141, it would be more desirable to procure improved derivatives of the Class 141. Accordingly, BR placed orders for two new models of the Pacer family with separate manufacturers, these being the Class 142 and Class 143 respectively.

The prototype was joined by another 20 two-car units which formed the Class 141 fleet. The units were used mainly in Yorkshire, operating on predominantly suburban services. They had a capacity of 94 passengers per two-car set, and two Leyland TL11 engines gave a total of , resulting in a top speed of . The Class 141s were built with standard Leyland National bodies, whose comparatively narrow width meant they could only be fitted with standard bus seating. The later Pacers had widened body panels to allow increased seating. Furthermore, in order to maximise cost savings, the manufacturers made use of road bus-standard electrical equipment, passenger fittings, and general cab layout wherever possible.

During 1988, in response to reliability problems related to the electronics used, the entire class was briefly withdrawn and underwent a technical upgrade in 1988 at the Hunslet-Barclay works in Kilmarnock. The reliability issue was largely resolved via the replacement of the original relay-based controller of the transmission with an alternative that was microprocessor-based. The units were permanently withdrawn from British Rail service in 1997. Many Class 141s were sold to Islamic Republic of Iran Railways.

Class 142

The next and largest Pacer class was the Class 142. As BR was considering ordering more railbuses, it was decided that, instead of placing these follow-on orders for further Class 141 vehicles, it would be more desirable to procure improved derivatives of the Class 141. Accordingly, BR placed orders for two new models of the Pacer family with separate manufacturers, these being the Class 142 and Class 143 respectively.

The Class 142 again was built by Leyland and BREL, in 1985. The body was based on a Leyland National bus, built at Workington in Cumbria. Many fixtures and fittings of the Leyland National could be found on the units. The new class had a greater capacity of 120 passengers per two-car set and the same engines were used. The first sets were used initially on Devon and Cornwall branch lines and on commuter services in the north west. The units from Cornwall were eventually moved to Liverpool and the north east, and the Class 142s became a common sight on services across the north of England.

The Class 142s received substantial upgrades during the early 1990s, which included the installation of more powerful Cummins engines, which gave a total power output of per two-car set. A number of units were then modified for use on the Merseyside PTE City Line on Merseyrail in the Liverpool region, which included dot-matrix route indicators, improved seating and Merseyrail PTE paintwork.

The Class 142s moved into the control of Arriva Trains Northern and First North Western at privatisation, and subsequently passed on to Northern Rail, Arriva Rail North, Northern Trains, Arriva Trains Wales and Transport for Wales. Eight Northern Rail units were temporarily withdrawn from service, replaced by a cascading of British Rail Class 158s. First Great Western

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