Class 99

Class 99

The Class 99 is a new generation of high-power bi-mode freight locomotive being introduced on the British main line network by GB Railfreight (GBRf). Built by Stadler Rail, owned by Beacon Rail and leased to GBRf, the class combines full-power 25 kV AC electric operation with a substantial onboard diesel engine for routes beyond the overhead wires.

A total of 30 locomotives, numbered 99001–99030, has been ordered. The Class 99 is based on Stadler's EURODUAL platform but extensively adapted to fit the smaller British loading gauge and meet UK signalling, safety and operational requirements.

Under the wires, the Class 99 develops 6,170 kW at the wheel, while its Cummins QSK50 diesel engine provides 1,790 kW away from electrification. With six powered axles and up to 500 kN starting tractive effort, it has been designed specifically for heavy freight rather than simply providing a low-powered "last mile" diesel capability.

The first locomotives arrived in Britain in 2025, followed by an extensive programme of testing, route proving and driver training. 99001 entered commercial service on 28 July 2026, hauling an intermodal service from DP World London Gateway to Hams Hall for Maritime Transport.

The class has also rapidly acquired an enthusiast nickname: "Flakes", a reference to the traditional 99 Flake ice cream.

This page brings together Class 99 information, history, specifications, nicknames, videos and sightings, providing a reference point for following one of the most significant new British freight locomotive classes for decades.

Class 99 technical specifications

Background and procurement

The Class 99 was developed to tackle one of the persistent problems facing British rail freight: the railway is only partly electrified.

Many important freight routes contain long stretches of 25 kV electrification, but freight terminals, ports, quarries and industrial branches are often beyond the wires. A conventional electric locomotive therefore cannot necessarily take a train from origin to destination without another locomotive being provided.

The practical result has historically been that diesel locomotives often work for hundreds of miles beneath overhead wires simply because they are capable of completing the entire journey.

This operational flexibility is one of the reasons the Class 66 became so successful. A diesel locomotive can go almost anywhere its route availability permits, without an operator having to plan a change of traction around the limits of the electrified network.

In April 2022, Stadler, Beacon Rail and GB Railfreight announced an agreement for 30 Class 99 locomotives. The programme represents an investment of around £150 million.

Rather than abandoning the flexibility that made diesel freight traction successful, the Class 99 attempts to retain it while allowing much greater use of electric power.

Where overhead wires are available, it can behave as a high-performance electric freight locomotive. When the wires end, it can lower its pantograph and continue using its onboard diesel generating equipment.

For GBRf, this makes it possible to reduce diesel operation without waiting for every freight terminal and connecting line in Britain to be electrified.

Based on the Stadler EURODUAL

The Class 99 belongs to Stadler's EURODUAL family of six-axle locomotives.

EURODUAL locomotives were developed for heavy freight operation on European networks where trains may need to work across different traction systems or over sections without electrification.

The British Class 99 uses the same basic philosophy but has been redesigned for the considerably more restrictive British loading gauge. The UK version is therefore narrower and lower than its continental relatives.

It retains the EURODUAL's Co-Co arrangement, with six individually powered axles carried on two three-axle bogies.

That is an important distinction between the Class 99 and several other recent British bi-mode locomotives. The Class 99 was conceived as a heavy-haul locomotive, rather than primarily as a mixed-traffic locomotive with an auxiliary diesel capability.

Electric operation

Under 25 kV AC overhead electrification, the Class 99 can deliver approximately 6,170 kW at the wheel.

That is more than 8,000 horsepower and gives the locomotive considerably more power than a conventional British diesel freight locomotive.

The electric traction system uses an inverter for each axle and provides a continuous tractive effort of approximately 430 kN, with starting tractive effort of up to 500 kN.

High electric power is useful for freight for more than simply maximum speed. Heavy trains require substantial power during acceleration and when climbing gradients, and freight performance can affect the capacity of a mixed-traffic railway when slower trains have to fit between faster passenger services.

The Class 99's electric performance is therefore intended to allow heavy freight trains to accelerate more rapidly when operating beneath the wires.

Its electric braking system can operate regeneratively, returning electrical energy to the supply where infrastructure permits, as well as providing rheostatic braking.

Diesel operation

Away from the overhead wires, the locomotive uses a Cummins QSK50 diesel engine.

The QSK50 is a large 50-litre V16 engine producing approximately 1,790 kW for the Class 99's diesel-electric traction system.

This is a significant part of the Class 99 concept.

Some earlier electric locomotives with onboard diesel engines have relatively small engines intended mainly for shunting, accessing terminals or covering short unelectrified sections. The Class 99 instead has enough diesel power to perform meaningful main-line freight work away from the wires.

Its diesel output is still substantially lower than its electric output, so the locomotive's strongest performance is achieved beneath electrification. But the diesel installation means that loss of the overhead supply does not automatically mean the end of the journey.

The engine complies with Stage V emissions requirements.

GBRf has also committed to using HVO — hydrotreated vegetable oil — or other renewable fuel rather than conventional fossil diesel for Class 99 operations away from the wires.

The environmental impact of HVO depends on how the fuel is produced and sourced, so it should not simply be described as zero-emission fuel. However, combining renewable fuel with extensive use of electric traction has the potential to reduce the carbon impact of suitable freight diagrams substantially compared with conventional diesel-only operation.

Is the Class 99 a hybrid locomotive?

GB Railfreight commonly describes the Class 99 as a hybrid locomotive, although bi-mode or electro-diesel is the more precise technical description of its traction arrangement.

It has two principal sources of traction energy:

• 25 kV AC electricity collected from the overhead line
• Diesel-generated electricity when operating away from the wires

Unlike the Class 93, the Class 99 does not rely on a traction battery as a third source of power.

The important point is that the locomotive can change traction mode during a journey and continue hauling the same train without requiring a locomotive change.

Class 99 nickname: "Flakes"

The Class 99 has already acquired the informal enthusiast nickname "Flake", or more commonly "Flakes" when referring to the class as a whole.

The explanation is simple: a traditional British ice cream cone served with a Cadbury chocolate Flake is widely known as a 99 Flake.

The connection was being suggested by railway enthusiasts even before the locomotives arrived in Britain and became increasingly common once testing began. References to the Class 99s as "Flakes" can now regularly be found in enthusiast discussion, captions and railway photography.

"Ice creams" is also occasionally used as an extension of the same joke, although "Flakes" appears to be the more established nickname.

The nickname is entirely unofficial. GBRf, Beacon Rail and Stadler continue to refer to the locomotives simply as the Class 99.

Appropriately, the connection was not lost on the industry either: ice cream featured at GBRf's 2025 Class 99 launch event.

The other Class 99: British Rail's train ferries

The designation Class 99 actually has an unusual railway history.

Long before the new Stadler locomotives appeared, British Rail used the Class 99 designation within TOPS for a fleet of ships — particularly train ferries operated by or associated with Sealink.

TOPS was designed around railway rolling stock. To allow ships carrying railway vehicles to be represented within the computer system, train ferries were effectively treated as locomotives hauling the trains carried aboard them.

They were consequently allocated numbers in the 99xxx series.

This means the modern 99001 is not the first item of railway equipment ever associated with that number.

The old use of Class 99 has occasionally inspired suggestions that the new locomotives should be nicknamed "Ships", but that has not achieved the same widespread enthusiast use as "Flakes".

It is nevertheless one of the stranger pieces of history surrounding the new class: a TOPS number once used to represent cross-Channel ferries has returned more than half a century later for some of Britain's most powerful freight locomotives.

Building and testing the Class 99

The Class 99s are manufactured at Stadler's Valencia plant in Spain.

The first locomotive, 99001, began taking shape during 2023, while 99002 became the first completed member of the class to receive major public exposure when a Class 99 was displayed at the InnoTrans 2024 railway exhibition in Berlin.

During early 2025, 99001 and 99002 underwent testing at the Velim railway test circuit in the Czech Republic.

The first two locomotives subsequently arrived in Britain in June 2025, landing at Bristol before being moved to Leicester.

Their arrival did not mean they could immediately enter normal freight service. Introducing a completely new locomotive involves far more than demonstrating that it can move a train.

Testing included areas such as:

• braking and traction performance
• operation under 25 kV overhead equipment
• diesel-mode performance
• signalling and train-protection compatibility
• electromagnetic compatibility
• gauging and infrastructure compatibility
• route testing
• driver training
• fault response and recovery
• maintenance procedures

The locomotives consequently appeared on numerous test and proving workings during 2025 and 2026 before regular commercial operation began.

Authorisation for operation

An important milestone came on 21 October 2025, when the Office of Rail and Road (ORR) authorised the Class 99 for placing into service.

The type was subsequently entered on the UK's Register of Authorised Types of Railway Vehicles.

Authorisation of the vehicle type was not the end of the introduction process. Network Rail compatibility work, individual route acceptance, operational readiness and driver training still had to be completed before the locomotives could be used freely on commercial services.

In May 2026, Network Rail granted the fleet an Interim Network Rail Statement of Compatibility, allowing the Class 99 introduction programme to progress further while work continued towards full compatibility certification.

By that stage, GBRf had formally accepted the first six locomotives, allowing driver training to increase ahead of commercial operation.

First freight trials

One of the most significant pre-service milestones occurred on 17 June 2026, when a Class 99 hauled a live intermodal train between DP World London Gateway and Maritime Transport's Hams Hall Rail Freight Terminal.

Unlike many earlier test workings, this placed the locomotive in the environment for which it had actually been purchased: hauling a real heavy freight service over a route combining electrified main line running with access to freight terminals.

The successful trial was one of the final stages before the beginning of commercial Class 99 operation.

First commercial Class 99 service

The Class 99 officially entered commercial service on 28 July 2026.

99001 worked the first revenue-earning service, hauling an intermodal train from DP World London Gateway to Hams Hall Rail Freight Terminal in the West Midlands for Maritime Transport.

This was a major transition in the history of the class.

For several years the Class 99 story had been one of computer models, manufacturing, exhibitions, test tracks, delivery photographs and proving runs. From July 2026 it became an operational British freight locomotive.

The London Gateway–Hams Hall working also demonstrated exactly the type of traffic for which the locomotive was conceived: heavy intermodal freight travelling between major logistics terminals while making use of electric traction wherever infrastructure permits.

As more locomotives are delivered and accepted, Class 99 operation is expected to spread across a wider range of GBRf freight diagrams.

Maintenance at Leicester

The Class 99 fleet is maintained by Stadler Rail Services.

Stadler was awarded a long-term service agreement covering the fleet for up to 16 years, including routine servicing, heavy maintenance, repairs, spare parts, technical support and maintenance data.

A dedicated facility at Leicester serves as the principal home for the Class 99 fleet.

The arrangement means Stadler is responsible not just for manufacturing the locomotives but for supporting them through a substantial part of their working lives.

Modern locomotive maintenance also increasingly involves remote monitoring and diagnostics. The Class 99 incorporates an advanced vehicle control and diagnostic system intended to identify faults and assist maintenance teams before problems result in extended downtime.

Driver's cab and safety systems

The Class 99 has a cab at each end with a centrally positioned driving desk.

Stadler designed the cab around visibility and ergonomics, with a large windscreen and camera systems providing additional views of areas including the pantograph, track ahead and shunting zones.

British train protection equipment includes:

• AWS — Automatic Warning System
• TPWS — Train Protection and Warning System

The locomotive has also been designed to accommodate ETCS — European Train Control System equipment as Britain moves towards greater use of digital signalling.

The cab incorporates modern climate control and diagnostic displays, providing a substantially different working environment from locomotive designs dating from the 1990s and earlier.

Class 99 vs Class 66

The locomotive most frequently associated with the Class 99 is inevitably the Class 66.

Class 66s have dominated British freight since their introduction at the end of the 1990s. Their success came from reliability, relative simplicity and, importantly, the ability to operate almost anywhere without dependence on electrification.

The Class 99 tries to retain that operational flexibility while addressing one of the Class 66's biggest disadvantages: a Class 66 remains diesel-powered even when travelling beneath hundreds of miles of overhead electrification.

The key difference is therefore not simply age or horsepower.

A Class 99 can use electricity for the electrified part of a journey and then continue under its own power when it reaches an unelectrified terminal or branch.

It also has substantially greater power available in electric mode, which should provide better acceleration for heavy trains where infrastructure and load permit.

The Class 99 should therefore be viewed as a means of displacing Class 66 operation on suitable diagrams, rather than necessarily as a simple one-for-one replacement for every Class 66.

Class 99 vs Class 88

The Class 88, also built by Stadler, introduced the concept of modern bi-mode electric freight traction to Britain before the Class 99.

However, the two designs have different priorities.

The Class 88 is a Bo-Bo locomotive with four powered axles. It provides approximately 4 MW under the wires, but its diesel engine produces only around 750 kW.

That diesel capability is extremely useful for accessing unelectrified terminals and covering shorter gaps in electrification, but electric operation remains very much the Class 88's primary role.

The Class 99 is a much heavier-duty proposition.

Its Co-Co wheel arrangement, 6.17 MW electric output, 1.79 MW diesel engine and 500 kN maximum starting tractive effort give it substantially greater heavy-haul capability, particularly away from the wires.

Class 99 vs Class 93

The Class 93 is another modern Stadler locomotive for the British network, but again it serves a different role.

The Class 93 is a Bo-Bo tri-mode locomotive capable of using:

• 25 kV electric power
• a diesel engine
• traction batteries

Its batteries can provide an additional power boost alongside the diesel engine and can also support low-emission operation away from overhead electrification.

The Class 93 is also significantly faster, with a maximum speed suitable for mixed-traffic and passenger work.

The Class 99 sacrifices that higher maximum speed in favour of six powered axles, greater tractive effort and substantially greater heavy-freight capability.

In simple terms, the Class 93 is a fast and flexible mixed-traffic locomotive; the Class 99 is the heavier hauler.

Why the Class 99 matters

The Class 99 is important because it provides a practical response to the awkward halfway stage in which Britain's railway currently finds itself.

A fully electrified freight network could rely almost entirely on electric locomotives. A completely unelectrified railway would favour diesel or another self-powered traction system.

Britain has neither.

Major routes such as sections of the West Coast Main Line and East Coast Main Line are electrified, while important freight branches, terminals, port connections and diversionary routes remain without wires.

That makes a powerful bi-mode locomotive particularly useful.

The Class 99 can take advantage of infrastructure that already exists without losing the ability to serve locations that have yet to be electrified.

It is therefore both a modern electric locomotive and, in some respects, a locomotive designed around one of the oldest problems in British railway operation: getting the train all the way to its destination.

Environmental significance

Much of the publicity surrounding the Class 99 has understandably focused on emissions.

GBRf has stated that Class 99 operation can reduce emissions by more than half on a typical journey compared with conventional diesel traction, although the actual saving on any individual service will depend heavily on how much of the route can be operated electrically.

A train operating predominantly beneath 25 kV wires should naturally achieve a much larger reduction in diesel use than one spending most of its journey on an unelectrified route.

The class does not therefore remove the case for further railway electrification.

Arguably, it strengthens it.

Every additional section of useful freight route equipped with overhead electrification gives a Class 99 another opportunity to turn off its diesel engine and use electricity instead.

Bi-mode traction and further electrification are consequently complementary rather than competing approaches.

Class 99 videos and sightings

The introduction of a completely new locomotive class provides an unusual opportunity to document its history almost from the beginning.

Early Class 99 videos and sightings include manufacturing and exhibition appearances, the Velim testing programme, delivery to Britain, test workings, route proving, driver training, freight trials and the first commercial services.

As the fleet grows, these records can help show how Class 99 operation develops across the network and how individual locomotives move between routes, terminals and traffic types.

Fishplate brings those videos and sightings together so that footage of the class can be explored alongside structured railway data.

FAQ

What is the Class 99?

The Class 99 is a high-power bi-mode Co-Co freight locomotive built by Stadler for use by GB Railfreight in Britain.

It can operate as an electric locomotive from 25 kV AC overhead wires and as a diesel-electric locomotive on non-electrified railway lines.

Who builds the Class 99?

The Class 99 is built by Stadler Rail at its Valencia facility in Spain.

Who operates the Class 99?

The Class 99 is operated by GB Railfreight (GBRf).

Who owns the Class 99 locomotives?

The fleet is owned by Beacon Rail and leased to GB Railfreight.

How many Class 99 locomotives are there?

30 locomotives have been ordered.

They are numbered 99001 to 99030.

What is the Class 99 nickname?

The most common enthusiast nickname for the Class 99 is "Flake" or "Flakes".

It comes from the 99 Flake, the familiar British ice cream cone served with a chocolate Flake.

Some enthusiasts also refer to them as "ice creams", although "Flakes" is more commonly encountered.

Neither is an official railway name.

Why is the Class 99 called a Flake?

Because its class number is 99, enthusiasts quickly made the connection with the 99 Flake ice cream.

Suggestions of the nickname appeared before the first locomotives arrived in Britain and it became increasingly common during testing and entry into service.

Has Class 99 been used as a railway classification before?

Yes — in a very unusual way.

Under British Rail's TOPS system, Class 99 was previously allocated to train ferries, many associated with Sealink, because the computer system needed to treat ships carrying railway vehicles as though they were locomotives.

The modern Stadler locomotives therefore reuse a class designation with a surprisingly maritime history.

Is the Class 99 diesel, electric or hybrid?

It is a bi-mode electro-diesel locomotive.

It operates electrically beneath 25 kV overhead wires and uses an onboard diesel engine to generate traction power away from electrification.

GB Railfreight also markets the locomotive as a hybrid freight locomotive.

Does the Class 99 have batteries?

Not as a main traction mode.

Unlike the Class 93, which combines electric, diesel and battery power, the Class 99's principal traction modes are 25 kV electric and diesel-electric.

What engine does the Class 99 use?

The Class 99 uses a Cummins QSK50, a 50-litre V16 diesel engine.

It produces approximately 1,790 kW in the Class 99 installation.

What fuel does the Class 99 use?

GB Railfreight has committed to operating the Class 99 using HVO or other renewable fuel when diesel operation is required.

HVO stands for hydrotreated vegetable oil.

How powerful is the Class 99?

The Class 99 can produce approximately:

• 6,170 kW in electric mode
• 1,790 kW from its diesel engine

Its maximum starting tractive effort is approximately 500 kN.

How fast is a Class 99?

The maximum speed is 120 km/h, equivalent to approximately 75 mph.

What is the wheel arrangement?

The Class 99 has a Co-Co wheel arrangement.

This means it has two bogies containing three powered axles each, giving the locomotive six powered axles in total.

How heavy is the Class 99?

A Class 99 weighs approximately 113 tonnes.

What is the Class 99 based on?

The Class 99 is based on Stadler's EURODUAL locomotive platform.

The design has been substantially adapted to fit the British loading gauge and comply with British railway systems and standards.

When did the first Class 99 arrive in Britain?

The first Class 99 locomotives arrived in Britain in June 2025.

They subsequently underwent testing, commissioning and route proving before commercial service began.

When did the Class 99 enter service?

The first commercial Class 99 service ran on 28 July 2026.

99001 hauled an intermodal freight train between DP World London Gateway and Hams Hall Rail Freight Terminal.

What was the first Class 99 commercial service?

The first revenue-earning Class 99 working was operated by 99001 for GB Railfreight on 28 July 2026.

It hauled intermodal freight from DP World London Gateway to Maritime Transport's Hams Hall Rail Freight Terminal in the West Midlands.

Where are Class 99 locomotives maintained?

The Class 99 fleet is principally maintained at a dedicated Stadler facility in Leicester.

Stadler has a long-term service agreement covering maintenance and technical support for the fleet.

Does the Class 99 replace the Class 66?

The Class 99 is intended to displace diesel-only locomotives such as the Class 66 on suitable freight workings, particularly those where substantial parts of the journey are electrified.

It should not necessarily be regarded as a direct replacement for every Class 66.

How does the Class 99 compare with a Class 66?

A Class 66 is entirely diesel-powered.

A Class 99 can use high-power electric traction beneath overhead wires and then continue under diesel-electric power where electrification ends.

This allows diesel fuel use to be substantially reduced on suitable routes without requiring a locomotive change.

How does the Class 99 compare with the Class 88?

Both are Stadler bi-mode locomotives, but the Class 99 is designed for significantly heavier freight duties.

The Class 88 is a Bo-Bo with around 4 MW electric power and a comparatively small diesel engine.

The Class 99 is a Co-Co, produces approximately 6.17 MW electrically and has a much larger 1.79 MW diesel engine.

How does the Class 99 compare with the Class 93?

The Class 93 is a faster Bo-Bo tri-mode locomotive using electric, diesel and battery power.

The Class 99 is a larger Co-Co bi-mode locomotive designed around heavy freight haulage, with greater tractive effort and considerably more diesel power.

Is "British Rail Class 99" the correct name?

The modern locomotive is normally referred to simply as the Class 99, GBRf Class 99 or Stadler Class 99.

The phrase British Rail Class 99 can be confusing because Class 99 was previously used by British Rail within TOPS for train ferries.

However, "British Rail Class 99" is also commonly used online as a generic description of the modern British locomotive class, so it is not useful to treat the phrase as simply "wrong".

Why is the Class 99 important?

The Class 99 combines the high performance and lower direct emissions of electric traction with the ability to reach unelectrified freight terminals and branches.

That makes it particularly suited to Britain's partially electrified railway and potentially allows much more existing overhead electrification to be used for freight without sacrificing the operational flexibility traditionally provided by diesel locomotives.