British Rail Class 88

The British Rail Class 88 is a type of mainline mixed traffic electro-diesel locomotive manufactured by Vossloh España/Stadler Rail Valencia for Direct Rail Services (DRS) in the United Kingdom. The locomotive is part of the Stadler Euro Dual family. It is the first dual-mode locomotive in the UK to use the 25 kV AC electrification.

Amid the fulfillment of DRS' order for the, Vossloh's team proposed the development of a dual-mode locomotive that could be alternatively powered by an onboard diesel engine or via electricity supplied from overhead lines (OHLE). Having been impressed by the concept, DRS opted to place an order for ten Class 88s during September 2013. Having been developed alongside the Class 68, considerable similarities are shared between the two locomotives, amounting to roughly 70per cent of all components being shared.

Testing of the first Class 88 was undertaken at the Velim Test Centre in the Czech Republic during 2016; these trials proved to be relatively smooth. During July 2016, 88001 made the type's first official public appearance. During January 2017, 88002 Prometheus was the first Class 88 to be delivered to the UK. All ten Class 88 locomotives were delivered by March 2017. During June 2017, the type entered regular service with DRS; examples have been typically used to haul freight trains, although they are also fitted for hauling passenger services as well.

Origins
During January 2012, Direct Rail Services (DRS) announced that it had ordered a total of 15 new diesel locomotives from Vossloh España (since 2016 Stadler Rail Valencia). These locomotives, which entered service in the UK as, were part of the company's Eurolight family, redesigned to fit the smaller UK loading gauge. DRS had opted to procure a clean-sheet design after examining various existing alternatives, such as the ubiquitous British Rail Class 66 locomotive, which the company's management determined to be incapable of satisfactorily replacing its ageing fleet of s, largely due to inefficient engines and elevated operating costs. Vossloh undertook development of the Class 68 over an 18-month period, during which the company studied several derivatives and modifications, including the use of alternative powerplants. Having presented such proposals to DRS, the latter became particularly interested in the electro-diesel arrangement, as the company's management recognised there was a potential role for a dual-mode locomotive in the UK market.

During September 2013, DRS announced that it had placed an order for a further ten locomotives, which were designated as the Class 88. The most distinctive difference between the news locomotives and the preceding Class 68 was that the former would harness a dual-mode electro-diesel propulsion system. Accordingly, these locomotives could be powered either via overhead lines (OHLE) or by an onboard diesel engine. In comparison to conventional diesel locomotives, this arrangement enables operational costs to be significantly reduced when diagrammed on routes partially or entirely under OHLE, under which the diesel engine can be deactivated. The Class 88 is the first dual-mode locomotives in the UK to use the 25 kV AC electrification, as the only other electro-diesel locomotives to have entered service on the British network were the and, which operated in the Southern Region using third rail electrification.

Specification
The Class 88 is part of the Stadler Euro Dual family. This is a range of dual-mode locomotives that are fitted both with a pantograph, to collect electricity from overhead wires, and a Caterpillar diesel engine. The UK version is able to run either on electrified lines using the pantograph, which is the UK's standard OHLE current at 25 kV AC, or away from electrified lines with the Caterpillar C27 950 hp engine. Dual-mode locomotives have previously been mooted for freight use in the UK, using the "Last Mile" principle, where a primarily electric locomotive is fitted with a small diesel engine to allow locomotives to run without a load to non-electrified freight sidings. However, the Class 88 is a fully dual-mode locomotive, with the diesel engine powerful enough to haul a train on its own, although with only 17.5per cent of the power it would otherwise have in electric mode.

In the majority of its aspects, the Class 88 featured a high degree of commonality with the preceding Class 68, including the use of an identical bodyshell, cab, brakes, bogies, traction equipment, control software; roughly 70 per cent of all components are shared between the two classes. Akin to the Class 68, the Class 88 can achieve a maximum speed of 100 mph, sufficient for regular passenger operations, while operating under OHLE, it has a power output of 4000 kW. Under diesel power, provided by its 12-cylinder Caterpillar C27, it has a maximum power output of 700 kW; however, the maximum tractive effort is available in either mode. The locomotive's engine, which is compliant with the current EU Stage IIIB emission restrictions, has limited available power as a result of the customer's choice to give the Class 88 comparable power to a traditional Class 20.

The Class 88 is outfitted with both dynamic and regenerative braking systems for the locomotive, along with air braking apparatus for the whole train. When applying regenerative braking, up to 4MW of power may be returned to the OHLE via the catenary. For electricity generation while operating under diesel power, the engine drives an additional traction motor that functions as an alternator, thus avoiding the need for installing a bespoke alternator. According to rail industry periodical Rail, the Class 88 has acceleration comparable to a modern family car when operating 'light', typically taking 13seconds to accelerate from stationary to 60 mph.

Testing and delivery
During April 2016, the first example of the class, 88001, was dispatched to the Velim Test Centre in the Czech Republic, which it was subject to a series of proving trials. The vehicle approvals process included the hauling of a 1,500-tonne train, along with repetitive tests under differing conditions to judge performance; particular attention was paid to the switching process between diesel and electric modes. The various electrified lines of the UK feature around 35 different variations of catenary; the interface between these diverse types and the Class 88's pantograph was a critical part of the acceptance process. According to rail industry periodical Rail, the data gathered during the type's trials showed promising results. During July 2016, 88001 made the class's first official public appearance, while 88003 was exhibited at InnoTrans two months later.

During January 2017, 88002 Prometheus became the first of the class to be delivered to the UK, arriving via the Port of Southampton and being transferred by road to the Carlisle Kingmoor TMD. 88 002 was initially used for homologation purposes to secure approval from the Rail Safety and Standards Board (RSSB) for the type's operation in the UK. All ten Class 88 locomotives were delivered by March 2017. During July 2017, it was announced that the Class 88 had entered into revenue service with DRS in the previous month, three examples having been used to haul freight trains within the first four weeks of operations. Initially, use of the onboard diesel engines was avoided while sufficient training was delivered to all drivers on the class and minor modifications were being made by the manufacturer.

Operation
DRS has procured the Class 88 to serve as a mixed-traffic locomotive, capable of operating both passenger and freight services. Primarily, the type has been used by DRS to haul freight using electric locomotives without the need to hire in electric traction from other operators. As with the Class 68, they are also capable of operating passenger trains.

Even prior to the type entering service, it was decided that the first duty of DRS' Class 88 fleet would be the contracted services between Daventry and Mossend on behalf of the supermarket chain Tesco. The service's path has been timed for an electric locomotive, and previously necessitated the use of a pair of Class 68s working in multiple. Other diagrams for the Class 88 have been focused on those that have previously been run under the wires with diesel traction.

Named locomotives
The names given to Class 88 locomotives are as follows:

Eight of these (88002 and 88004–10) revive names previously carried by Class 76 and 77 (EM1 and EM2) electric locomotives built in the 1950s for the "Woodhead" electrification.

Models
In conjunction with Rails of Sheffield, Dapol are producing a model of the Class 88 in OO scale. Four examples (88001, 88003, 88007, and 88010) are expected.