Rolling stock • Locomotive • Great-Britain • GBRf • Class 99
Summary: GBRf CEO John Smith has long argued that Class 66s will eventually need replacing to support freight growth, particularly as the industry must decarbonise. Progress depends heavily on infrastructure, notably wider electrification, which Smith has consistently advocated, though with limited government backing. Seeking alternatives, GBRf worked with Stadler to develop a bi-mode solution: the Class 99. Thirty Class 99 EuroDual-based locomotives have been ordered, featuring a 75mph top speed and Co-Co layout, with the first units arriving in the UK during summer 2025.
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In brief
GBRf CEO John Smith has long warned that the Class 66 fleet will need replacing if freight is to grow, particularly as the industry must decarbonise. Progress depends on infrastructure decisions, notably electrification, which Smith has consistently advocated for key freight routes such as Felixstowe, though with limited government support. As decarbonisation pressures increased, GBRf sought alternatives and, working with Stadler, developed a UK-specific version of the EuroDual: the bi-mode Class 99.
Thirty Class 99 locomotives have been ordered, featuring a 120 km/h top speed and Co-Co wheel arrangement. The first two units were unveiled and tested in Europe and are due in the UK this summer. Speaking at a rail conference, GBRf’s Dave Golding highlighted freight’s national importance, efficiency advantages, and role in achieving net-zero targets. The Class 99 programme is both a sustainability statement and a practical solution, though production has been slightly delayed by severe flooding in Valencia, affecting later units and the supply chain.
| LOC TYPE | ||
|---|---|---|
| Family name: | EuroDual | |
| Class: | 99 | |
| Manufacturer: | Stadler | |
| Train type: | Bimode locomotive | |
| Sector: | Freight | |
| Owner: | Beacon Rail | |
| Operator(s): | GBRf | |
| First service: | December 2025 | |
| TECHNICAL | ||
| Lenght: | 23m | |
| Maximum speed: | 120 km/h | |
| Loco weight: | 113 t | |
| Electric system(s): | 25 kV AC | |
| Pantograph(s): | 2 | |
| Diesel motor(s): | Cummins QSK50 | |
| Batteries: | no | |
| Braking system(s): | regenerative, rheostatic | |
| Track gauge: | 1,435mm |
Background
The Class 66 has been central to UK rail freight for more than 25 years. Introduced in 1998, 480 new locomotives were delivered to Britain, with a further 27 imported, although later market changes saw 89 exported to Europe. During its expansion in the 2010s, GB Railfreight (GBRf) acquired the final new-build Class 66s before emissions regulations forced Electro-Motive Diesel to end production for the UK market. To maintain capacity, GBRf creatively imported 27 locomotives from Europe; 26 are now operational, with the final example expected to enter traffic soon.
GBRf chose the Stadler EuroDual to manage freight trains in the UK because it combines high power, efficiency, and flexibility. In april 2022, GB Railfreight (GBRf) and the leaser Beacon Rail have signed an agreement with Stadler for 30 class 99 Eurodual bi-mode Co-Co locomotives including spare parts.
Beacon Rail is own the new hybrid fleet, and GBRf is the lessee. The UK government’s electrification rollout, when complete, will enable the Class 99s to run on electricity across all UK routes and reduce emissions by 585,000 tonnes of carbon per year. High quality and reliable servicing is critical to ensuring the fleet can deliver this impact.
Why this choice?
GBRf Safety and Sustainability Director Dave Golding spoke about the new Stadler fleet at the Rail in Oxfordshire and the Midlands conference, organised by Modern Railways and held in Oxford, on 31 January 2025. He explains: ‘We know full well that we’d be waiting an awfully long time for electrification to reach some of the parts we serve, and if there are no wires and you don’t have a serious bi-mode, you have to go with a diesel.’
Dave Golding explains why the Class 66 locomotives have reached their limits in an increasingly congested British network: ‘Having sat in the front of a Class 66 many times trying to think of things to say to the driver as we wait for another red signal, it’s the time it takes to reach a speed when you’ve got 2,000 tonnes behind you. It can be 25 minutes before you get back to line speed when you’re pulling a heavy train.’ Stopping freight trains, he suggests, is counterproductive. ‘Passenger units are quite light by comparison, and the tractive effort generated by an electric unit of any description means it can get away and accelerate pretty quickly. It would seem more sensible if freight actually got green lights all the way and the passenger network was a bit more agile and nipped in between.’ Enter the Class 99. ‘The locomotive order is a sustainability project and statement in addition to providing much-needed new traction‘, suggests Dave Golding.
Another reason was the acceleration of the implementation of Great British Railways following the Labour Party’s arrival in power in the summer of 2024. GBR was not yet well known, but there were strong indications that passenger traffic would be given priority. The complaint was that freight trains were ‘cluttering up the timetable’ with their slowness, which reduced the capacity of the network. The Class 99 is therefore a tool for GBRf to demonstrate that freight trains can be accelerated more effectively to better integrate them into the density of rail traffic.
Technical
The EuroDual is a bi-mode locomotive, able to run on both electric and diesel power, which suits the UK’s partially electrified network and reduces reliance on diesel where overhead lines exist. The locomotive meets modern emissions standards, supporting GBRf’s sustainability goals and lower carbon strategy. In addition, Stadler’s proven reliability, advanced onboard technology, and strong maintenance support help improve operational performance, reduce downtime, and lower whole-life costs for freight operators in the UK.
The EuroDual design was squeezed into the UK loading gauge but the design features much in common with other EuroDual fleets which derisks any potential technological hurdles. The locomotive can therefore operate under the British 25kV system where overhead lines are available. On the many sections that are still not electrified, the Class 99 uses a diesel engine, a Cummins QSK50 capable of 1,800kW, meets Stage 5 emissions targets and is fuelled by HVO, further improving the environmental credentials of the Class 99.
The 120 km/h locomotive has a maximum tractive effort of “up to” 500 kN and a power rating of 6,170 kW in electric mode. These figures exceed those of the diesel-powered British Rail Class 66. It is fitted with the AWS and TPWS safety systems, and is planned to be fitted with ETCS. It has cameras providing views of the pantographs, shunting zones and the front of the locomotive.
Testing
The first Stadler Class 99 (99002) was first unveiled at Innotrans in Germany in September 2024. The second locomotive (99001) was loaded into a lorry at Stadler’s Valencia factory and has arrived in January 2025 at the VUZ Velim test centre in the Czech Republic for testing and commissioning.
For Stadler plans have changed with more certification work to be carried out at Velim. This follows experience gained from the ongoing introduction of the tri-mode Class 93s, also built by Stadler.
The first two Class 99 locomotives will move from Velim to Leicester in June 2025, arriving via Portbury Docks before entering UK Rail Leasing’s new Leicester facility, their base for at least five years. Until ORR certification is granted, they will remain on-site for static testing and training, with possible additional testing at the Severn Valley Railway. Once certified, separate diesel and electric trials will occur at alternative sites, as RIDC Asfordby is full. A main line debut is expected in September or October. No 99003 may stay in Spain or be shipped to the UK for static testing, training, and industry demonstrations.
The first locomotives were transported by lorry and then by ship because the Stadler Valencia factory is only connected to the Spanish network via the Iberian gauge, which is 1,668 mm. Furthermore, an uncertified locomotive cannot travel on the various national networks before reaching its destination, even if it is being towed as a “vehicle”.
Entering in service
GBRf currently leases and owns a large mixed fleet of 66s, while also progressing a programme to regear and renumber selected locomotives into the 66/6 subclass. GB Railfreight is considering returning some Class 66 locomotives as new Class 99 bi‑mode units continue to arrive, although no final decisions have been made end of 2025. Early returns would likely come from older Eversholt‑leased batches. 🟧
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Rolling stock • Locomotive • Great-Britain • GBRf • Lexical