BR Class 66

The BR Class 66 is a 3,300 horsepower heavy-freight diesel produced by Electro-Motive Diesel (EMD) in London, Ontario and La Grange, Illinois. The locomotive was manufactured based on the successful and reliable Class 59 locomotive, which was produced in a small order of 15. The Class 66 was so successful, that over 400 examples were produced for the UK.

Following the amalgamation of British Rail into various private enterprises in the late nineties, North America’s Wisconsin Central Ltd was looking to expand into the UK rail freight market. The result of the negotiations between existing rail companies, Loadhaul, Transrail, and Mainline, resulted in the formation of the English, Welsh, and Scottish Railway (EWS), which controlled a staggering 93% of rail freight in the UK.

Duncan Cotterill/railography

In order to compete with the competitive road transport system, EWS management sought to lower costs and make rail transport faster and more cost effective for the customer. To achieve this, EWS needed to introduce a locomotive that encompassed high availability, low maintenance costs, and ease of operation. In order to compete with these other modes of transport, it was imperative that the railway lessen the chance of mechanical failures.

Much of the traction acquired by EWS consisted of first generation British Rail diesels, and were in need of overhaul or replacement. Meanwhile, asphalt company Foster Yeoman had employed the reliable Class 59 locomotive in their various quarries throughout the country for a decade, while boasting high availability ratings and ease of maintenance. The Class 59 locomotive was the British variant of the highly successful SD40-2 in North America.

Richard Gunn

Availability and ease of maintenance was a necessity for the EWS due to its vast railway network. EWS management contacted EMD in 1996, resulting in an order of 250 Class 66 locomotives, which EMD had designated JT42CWR, at a cost of £345,000. These units were similar to the Class 59, however, included different prime movers, and radial trucks, which reduced wear on wheels and rails, especially on curves. Astoundingly, the locomotives were delivered in less than two years, with the first locomotive being delivered to the UK in early 1998, arriving at the port of Immingham. Upon delivery, the locomotive was taken to Derby for testing, and within two months, was hauling its first revenue train. The unit impressed EWS management with its performance, and ability to haul heavy trains at a high rate of speed, sometimes up to 75 mph.

The reliability and ease of maintenance of these locomotives was evident, as the locomotives had boasted a 95% availability, and soon additional orders were placed by EWS, along with orders from Freightliner, GBRf, and Direct Rail Services. By the end of production in 2016, 455 examples of the type were produced and delivered to the UK, and presently make up the majority of the nation’s freight motive power.

Although there are a number of reasons for the popularity of the class, the High Traction Radial Bogie (HTRB) is among the most important. Based on new electronics used on North American locomotives, these bogies lessen the impact of the locomotive on rail infrastructure, and on the wheel flanges, all while improving ride quality for the crews. Additionally, these types of bogies have a drastically improved factor of adhesion, which in turn, increased pulling power. The HTRB bogie operates by allowing each axle to steer into the curve instead of the bogie turning in one solid unit. This reduces the chance of wheel hunting, where the wheel oscillates in a side to side motion, and is more prone to derailing.

Side profile of radial bogie
Steve Jones

Similar to UK design, the locomotives featured a monocoque car body, with cabs on either end, which allows crews to easily change ends. The locomotives were popular with freight carriers because of the ability to haul many tonnes of freight a fair distance without the need for refueling, as the locomotives are equipped with a 6,400 litre fuel tank. The locomotive has a route availability of seven, allowing it to travel on most railways throughout the country. According to Rail Magazine, by 2002, the class had achieved a record 98% availability rating, and had gone 70,000 miles without a mechanical failure. These numbers make it easy to understand why the UK’s rail freight industry chose the Class 66 as the standard form of motive power for their operations.

In December 2002, due to stricter emission standards, new members of the class underwent extensive modifications, including larger radiators and exhaust treatments. Additionally, modified fuel injectors and pistons allows the units to operate at lower temperatures. A smaller fuel tank was also fitted in order to meet stringent weight restrictions.  This updated version of the class was classified under the TOPS system as Class 66/9.

Continental Europe

In addition to their use in the UK, railways throughout continental Europe saw the class as a viable locomotive due to its reliability and ease of maintenance. The class found use in Germany, the Netherlands, Sweden, Norway, Belgium, Denmark, France, and Poland. The locomotives operate on various routes throughout these countries, and continue to be a viable locomotive for their operations.

Gary Severn

Driver Concerns

Although popular for their power and reliability, locomotive drivers despised operating the units, as they believed the cab was unfit for operation due to noise and ergonomic complaints. Because the locomotive’s cab was not isolated from the frame, the crew felt the rumble and sound of the prime mover and radiator fan, which made train crews susceptible to hearing loss and other impairments. Additionally, because of the poor insulation between the cab and the power unit, the cab temperature rose dramatically, and made it uncomfortable for crew members. In addition to the UK operators, other railways throughout continental Europe complained about crew comfort, resulting in Norway’s CargoNet increasing pay to the crews operating the locomotives.

As a result, many drivers refused to operated the locomotives, and looked to the aid of their union, the Associated Society of Locomotive Engineers and Firemen (ASLEF), who proposed banning drivers from operating them. As a result, improved insulation was installed on many locomotives, and select locomotives received panel upgrades on the cab walls. The seating inside the cab was also refurbished to ensure driver comfort and support. After these modifications were introduced, drivers saw the class more suitable for operation, and were deemed sufficient for operation by ASLEF.

Leigh Caudwell


The Class 66 is powered by a 3,300 horsepower 12 cylinder EMD 12N-710G3B-EC, two stroke prime mover, and is capable of a tractive effort of 91,900 lbf. The Class 66 locomotive is an efficient, well rounded machine, supplying their operators with reliable service and offers unmatched availability. The Class 66 uses HTRB bogies, which are designed to increase wheel-rail adhesion on curves, and lessen the wear on both track infrastructure and wheels. Although the interior of the locomotive has not been popular with drivers due to noise, ride quality, and heat, it is simple and easy to operate, and includes various warning systems used in the UK, inlcluding  Automatic Warning System (AWS), which alerts crew members in the event of a passed signal or speed infraction.


BuilderElectro-Motive Diesel
Build Date1998-2008 (Ontario, Canada)

2014-2015 (La Grange, Illinois)

Number Built455
Wheel ConfigurationCo’Co’
BogiesHTRB Radial
Wheel Diameter1,066 mm
Minimum Curve80m
Weight129.6 tonnes
Fuel Capacity6,400 litres
Prime MoverEMD 12N-710G3B-EC
AlternatorGM-EMD AR8
Traction MotorsGM-EMD D43-TR
Train BrakesWestinghouse PBL Air
Max Speed75mph
Horsepower3,300 bhp
Tractive EffortMax: 91,900lbf


Brakeforce68 tonnes
Route Availability7





Current Operators:                                

Colas Rail

DB Cargo UK

Direct Rail Services


GB Railfreight

Former Operators:

English, Welsh, and Scottish (EWS)


Alexander Johnson

As a result of the European Union’s (EU) strict emissions standards, the last Class 66 locomotive was delivered to the UK in 2016, as it did not meet the regulations. In order for the class to meet the regulations, the units would need special exhaust treatments which would not be feasible due to the UK’s strict loading gauge. The last Class 66 delivered was painted in a special livery and named the “Evening Star”, after the last steam locomotive delivered by British Rail, Class 9F 2-10-0 No.92220 “Evening Star”, a heavy freight locomotive built at Swindon Works. Upon delivery, it was agreed that the last Class 66 was to be donated to the National Railway Museum upon retirement. Although the Class is no longer in production, it is most likely that the units will be present on UK railways for many years to come.


Lifelong Rail Enthusiast and Owner of Worldwide Rails

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