Transport for Wales Class 231 / 756 Stadler FLIRTs

[Snow1964]

Is this to basically limit the amount of diesel they use ?

Partly, the official reasons seem to include reducing noise in urban areas, less emissions and greener, and operational benefits

TfW says the conversion programme will deliver both operational and environmental benefits. By making greater use of electric traction, the trains will reduce diesel consumption, lower carbon emissions and decrease noise levels, particularly in urban areas and around stations.

Transport for Wales to Convert Class 231 Fleet into Hybrid Trains

Transport for Wales (TfW) has confirmed plans to upgrade its Class 231 fleet, with the diesel-electric trains set to be converted into hybrid units as part of the organisation's long-term decarbonisation strategy.The move follows an agreement between TfW, the Welsh Government and manufacturer...

www.saferhighways.co.uk

 

[SWML9102]

It makes sense to convert them. Sadly can't see them lasting long on Maesteg - Ebbw Vale services after conversion (if they ever get onto those routes). Unless someone is secretly planning more electrification

 

[enapace]

Partly, the official reasons seem to include reducing noise in urban areas, less emissions and greener, and operational benefits

Transport for Wales to Convert Class 231 Fleet into Hybrid Trains

Transport for Wales (TfW) has confirmed plans to upgrade its Class 231 fleet, with the diesel-electric trains set to be converted into hybrid units as part of the organisation's long-term decarbonisation strategy.The move follows an agreement between TfW, the Welsh Government and manufacturer...

www.saferhighways.co.uk

Thank you for the reply so this basically will make them 756s without the battery’s they have onboard.

 

[Envoy]

Could a hybrid 231 get from Severn Tunnel Junction to Cheltenham & back on battery stored electricity?

 

[Caaardiff]

I'm guessing being bi-mode there will be no battery power.

How much benefit will be gained when they will only be able to use the wires for 10 mins on the Ebbw Vale service and 30 mins in the Cheltenham service?

 

[Snow1964]

Could a hybrid 231 get from Severn Tunnel Junction to Cheltenham & back on battery stored electricity?

No, it's about 90 miles, and no plans for batteries.

BEMUs would be possible if say Seven Tunnel to Caldicot was electrified (a section relatively free of bridges), at least to Gloucester, but not onwards to Cheltenham.

Of course if Cheltenham-Gloucester area was electrified (even as say 6-10 miles) then yes, and of course would allow Battery trains on Bristol Parkway - Bromsgrove section too

 

[Trainbike46]

Thank you for the reply so this basically will make them 756s without the battery’s they have onboard.

They'll be 755s, like the ones operated by GA

== Doublepost prevention - post automatically merged: 4 Jun 2026 ==

I'm guessing being bi-mode there will be no battery power.

How much benefit will be gained when they will only be able to use the wires for 10 mins on the Ebbw Vale service and 30 mins in the Cheltenham service?

The 755s serve some routes with very little electrification, so the fact that they'll be bimode won't necessarily mean they're redeployed, though I could see a case for using them on routes from Cardiff with larger portions of electrified track.

 

[enapace]

They'll be 755s, like the ones operated by GA

== Doublepost prevention - post automatically merged: 4 Jun 2026 ==


The 755s serve some routes with very little electrification, so the fact that they'll be bimode won't necessarily mean they're redeployed, though I could see a case for using them on routes from Cardiff with larger portions of electrified track.

Thank you for the clarification I didn’t realise there was a actual number for them

 

[Cardiff123]

Unless this is incorrect reporting, the RAIL article states

Class 231s currently operate alongside ‘756s’ and Class 150s in South Wales but are due to move onto more main line and Vale of Glamorgan Line services once Class 398 tram-trains are rolled out on the South Wales Metro.

I thought that the VoG line will be getting 756s, hence why there has been late night testing of 756s on the VoG in recent months?
There's only 11 x 231s, keeping some on Rhymney - Bridgend (currently 4 diagrams at 1tph) won't leave many for the mainline

 

[Peter Sarf]

Thank you for the clarification I didn’t realise there was a actual number for them

In case you are confused.

Class 755 already exists (in Anglia).

With the 231 gaining pantographs they will be very much like the existing 755s (these are Bi-Mode so diesel and 25KV AC). Not like the existing 756s (these are tri-mode so diesel, 25KV AC AND battery).

I doubt the actual class number for the 231s will get changed, if it does it may not be 755 but perhaps 757. BUT that is for conjecture on separate thread.

 

[positron]

Really can't understand why they weren't built to hybrid specification in the first place.

Well when they were being procured there was talk of the wires not even reaching Cardiff. So it would be have been a bit pointless.

 

[Tram Inn SB]

Bi-Mode has been given the Green light for the Class 231 units:

Transport for Wales confirms '231' fleet will become bi-modes

Operator to fit pantographs to Class 231 FLIRT sets over the coming years.

www.railmagazine.com

== Doublepost prevention - post automatically merged: 3 Jun 2026 ==


I've just seen this as an aside, at least it's been made public now.

Fantastic news at last !

But…..would it have been cheaper to spec them as bi mode from day one ? Probably, but a win is a win.

 

[Tram Inn SB]

Definitely nice to see them officially confirm that now; I was reading the proposal documents/consultation responses for West Wales-Bristol Temple Meeds. There is mention in that (in a response to Network Rail) about future Burns stations, that Cheltenham services potentially will extend to Birmingham Moor Street so this conversion will definitely help save fuel for them to reach Birmingham should that materialise as we know Flirts have less range (ish) I believe versus something like a 197, and generally makes sense for the routes they will run. Mainline operation for 231s is from the December timetable change, right?

Source: https://www.orr.gov.uk/sites/defaul...lemental-agreement-consultation-responses.pdf (Page 17)

Without straying into speculation….there is a possibility of extending back to Birmingham New Street (cut in 2003), using the OLE from Bromsgrove in the UP direction and from Severn Tunnel in the DN.

The current XC service is hit and miss at best most days.

 

[Snow1964]

Really can't understand why they weren't built to hybrid specification in the first place.

Well when they were being procured there was talk of the wires not even reaching Cardiff. So it would be have been a bit pointless.

There was an option to add pantographs from the start (which was valid until 30th April 2026), this was confirmed in FOI answer 88_23 from TfW in June 2023 (sorry can't get it to link)

Presumably the option was exercised, but no one commented on it for at least 5 weeks

 

[tfw756rider]

Thank you for the reply so this basically will make them 756s without the battery’s they have onboard.

I'm guessing being bi-mode there will be no battery power.

They'll be 755s, like the ones operated by GA

In case you are confused.

Class 755 already exists (in Anglia).

With the 231 gaining pantographs they will be very much like the existing 755s (these are Bi-Mode so diesel and 25KV AC).

They'll be like the 755/4s in terms of traction, with 4 engines (but with the appearance and interior fitout of 756s). The 755/3s only have 2 engines, and the 756s only have one engine. No class number has been revealed yet, but I think 757 is most likely (out of the way of Greater Anglia, unlike 754 or 755/5). It will be changed, as the units will go from being diesel multiple units with electric transmission to overhead AC electric-capable bi-mode units.

 

[positron]

Is there precedent for this kind of diesel electric pantograph modification and whether it changed fleet numbers? The class 230 seemed to be a Hodge podge of different traction powers and they were all a single number so it seems fine to keep it as 231 (perhaps a /1) even if they're now pantographed?

 

[pokemonsuper9]

Is there precedent for this kind of diesel electric pantograph modification and whether it changed fleet numbers? The class 230 seemed to be a Hodge podge of different traction powers and they were all a single number so it seems fine to keep it as 231 (perhaps a /1) even if they're now pantographed?

Kind of the other way around, but 319s became 769s (and a hydrogen 799 [maybe 768s too, not sure what happened with them]).
I see no reason why the same wouldn't apply to a diesel train getting direct electric power.

And I think an ex-ScotRail EMU got put in the 6xx series then scrapped but I can't remember the details.

 

[tfw756rider]

Is there precedent for this kind of diesel electric pantograph modification and whether it changed fleet numbers? The class 230 seemed to be a Hodge podge of different traction powers and they were all a single number so it seems fine to keep it as 231 (perhaps a /1) even if they're now pantographed?

None of the 230s have received a pantograph though.

There's no way the bi-mode converted "231s" will remain 231s; once they have AC electric pickup capabilities they'll have to be reclassified as "electric" units or "AC electric-capable bi-mode units" in the (non-high-speed) 7xx range.

Don't be surprised if it's something like 757.

 

[MCR247]

None of the 230s have received a pantograph though.

There's no way the bi-mode converted "231s" will remain 231s; once they have AC electric pickup capabilities they'll have to be reclassified as "electric" units or "AC electric-hcapable bi-mode units" in the (non-high-speed) 7xx range.

Don't be surprised if it's something like 757.

(My bold)

Have you seen this stated or confirmed anywhere as a fact? Or is it just what you think/believe will happen? I have no inside knowledge either way, I’m just surprised at how certain you seem.

Personally, I can’t foresee a situation where TfW literally have to (as in they no choice at all) change the fleet class. Who would enforce this? And on what basis? Would the DfT or ORR really be that invested? Especially since in this case 2xx is meant to be Diesel-Electric and well they’ll still have both Diesel and Electric power, just not in the originally intended order

They may want to change the fleet number, say to make sure it’s very clear which have pans and which don’t during the conversion periods, or they could decide to go with a different subclass to show this. The latter would presumably be cheaper as it wouldn’t mean needing to change documentation etc.

There are things like the 319 to 769 conversions, but whether the fact that it wasn’t the entire fleet being converted made that more necessary, or whether it was more PR for the project, who knows.

Interestingly, we have the D Trains. All Class 230/0s but could be DEMUs, DBEMUs or BEMUs as I understand it.

If Project Thor had gone ahead and added pantograph cars to voyagers we’d have had a precedent there I guess

 

[tfw756rider]

(My bold)

Have you seen this stated or confirmed anywhere as a fact? Or is it just what you think/believe will happen? I have no inside knowledge either way, I’m just surprised at how certain you seem.

It's just what I believe, but I can't see them staying as 2xx - it just wouldn't make any sense, so wouldn't happen.

Personally, I can’t foresee a situation where TfW literally have to (as in they no choice at all) change the fleet class. Who would enforce this? And on what basis? Would the DfT or ORR really be that invested?

I can. Each number range has a meaning, and for what will be "non-high-speed bi-mode units" (7xx) to be 2xx would just be nonsense.

Especially since in this case 2xx is meant to be Diesel-Electric and well they’ll still have both Diesel and Electric power, just not in the originally intended order

2xx was originally (and in the more immediately following examples still is) diesel-electric multiple units (DEMUs). In other words, diesel multiple units with electric transmission, where the diesel engines drive alternators/generators that supply power for the electric traction motors, but the unit doesn't have an electric pickup (pantograph) so can't actually run from the overhead electricity supply. The 220s, 221s, 222s and (as-originally-built) 231s fit this exact description. The 205s, 207s and London Northwestern 230s also fitted this exact description.

They may want to change the fleet number, say to make sure it’s very clear which have pans and which don’t during the conversion periods

I really do believe that this is what will happen (based on the way the system works), and then they'd stay 7xx (rather than revert back to 2xx).

or they could decide to go with a different subclass to show this. The latter would presumably be cheaper as it wouldn’t mean needing to change documentation etc.

I really do think that this is highly unlikely, as it would go against the rules of Total Operations Processing System (TOPS) and Train Running Under System TOPS (TRUST).

There are things like the 319 to 769 conversions, but whether the fact that it wasn’t the entire fleet being converted made that more necessary, or whether it was more PR for the project, who knows.

The 319-to-769 conversions from AC electric to bi-mode were reclassified from 319 to 769 because their traction change necessitated a change from 3xx to 7xx class number. When Transport for Wales removed the pantographs from their 769s, they left the preparation for the unit to run on overhead AC electric power (just pop them back on), so they remained classified as "diesel-capable electric" bi-mode units, even though they removed the pantographs and only used the diesel mode.

Interestingly, we have the D Trains. All Class 230/0s but could be DEMUs, DBEMUs or BEMUs as I understand it.

The Transport for Wales 230s, whether running in diesel or battery mode, are self-powered units with electric traction motors but don't have a pantograph so can't actually run from the overhead supply. The Great Western Railway 230, though it doesn't have diesel engines and only has batteries, is still a self-powered unit with electric traction motors, but that doesn't have a pantograph so can't actually run from the overhead supply. 2xx obviously does allow these, so 2xx nowadays is for self-powered units with traction motors that can't connect to railways' electrification (on the move), whether they have batteries (BEMU) or diesel engines (DEMU), or both (DBEMU).

If Project Thor had gone ahead and added pantograph cars to voyagers we’d have had a precedent there I guess

As they would've become higher-speed bi-mode units, it would've been the first use of an 8xx class number, predating the Hitachi AT300 Class 800 designation by 3-4 years. Just that as it didn't happen, 8xx didn't end up first being used until 2014 for Class 800 (Hitachi AT300), even though the 6xx, 7xx and 8xx numbering ranges already existed in 2010 I believe.

So a long explanation, but I hope it helps with understanding why the bi-mode-converted 231s will be reclassified with a 7xx class number

 

[stormcoffeecat]

Transport for Wales confirms '231' fleet will become bi-modes

Operator to fit pantographs to Class 231 FLIRT sets over the coming years.

www.railmagazine.com

Transport for Wales has confirmed it is planning to convert its Class 231 diesel-electric units into bi-modes.

The fleet of 11 Stadler-built sets will have pantographs fitted over the coming years after TfW decided to activate a Hybrid Variation Agreement with the manufacturer.

Class 231s currently operate alongside ‘756s’ and Class 150s in South Wales but are due to move onto more main line and Vale of Glamorgan Line services once Class 398 tram-trains are rolled out on the South Wales Metro.

TfW Chief Commercial Officer, Alexia Course, said: "We can confirm that work is being mobilised to convert our Class 231 fleet into hybrid trains, following approval and funding from the Welsh Government and agreement with our delivery partners.

"This programme will reduce reliance on diesel, cut emissions and noise, and give us greater flexibility to operate the fleet more efficiently across the network, supporting our longer-term decarbonisation ambitions.”

Course said work will be “delivered on a phased basis over several years”.

Congrats on their transition

 

[Russel]

Wonder what the cost of retrofitting a pantograph now is over just ordering them with it from new?

 

[DelW]

Interestingly, we have the D Trains. All Class 230/0s but could be DEMUs, DBEMUs or BEMUs as I understand it.

Not all the D78s became 230s - the Island Line ones (which are EMUs, running on 3rd rail) became 484s. AFAIK none of the 230s can run on electric power collected on the move, via pantographs or collector shoes, although the GWR prototype can collect power while stationary.

 

[Jorge Da Silva]

Will the Class number change?

 

[Crithylum]

Wonder what the cost of retrofitting a pantograph now is over just ordering them with it from new?

Seems like TfW have activated a clause in the original contract, so I would assume not much.

 

[TT-ONR-NRN]

None of the 230s have received a pantograph though.

There's no way the bi-mode converted "231s" will remain 231s; once they have AC electric pickup capabilities they'll have to be reclassified as "electric" units or "AC electric-capable bi-mode units" in the (non-high-speed) 7xx range.

Don't be surprised if it's something like 757.

Do you have a source for that?

 

[DelW]

Will the Class number change?

No one (on here at least) knows for sure, but it would be logical to change them to a 7xx class number, probably 757 - see the comprehensive summary in post #3320 for reasons.

However, class numbers aren't always logical, so there's no guarantee.

 

[SuperLuke2334]

If these are having pantographs added, I wonder whether they'll be upgraded to 100mph maximum speed at the same time? Seeing as I believe they are currently limited at 90?

 

[positron]

If these are having pantographs added, I wonder whether they'll be upgraded to 100mph maximum speed at the same time? Seeing as I believe they are currently limited at 90?

Probably not worth it till the relief upgrades happen and even then idk how much 100 there will actually be to use.

As I understand it, it's all based on gearing configuration being capped at 90 gives them faster acceleration (though I might have misunderstood). I seem to recall reading it's not a difficult thing to change.

 

[craigybagel]

Probably not worth it till the relief upgrades happen and even then idk how much 100 there will actually be to use.

As I understand it, it's all based on gearing configuration being capped at 90 gives them faster acceleration (though I might have misunderstood). I seem to recall reading it's not a difficult thing to change.

There isn't even 100mph on the mains at the monument. Nowhere on the currently planned 231 routes features 100mph running.