TfW class 398 Stadler Citylink tram trains

[VR494]

Attached is a picture taken at Cardiff Bay during testing on Thursday last week, where a pair of 398’s underwent battery testing.

3Q41 formed of a pair of 398’s about to depart with a test train to Radyr.

 

[positron]

Taken at the end of last week while conducting tests on the batteries at Cardiff Bay station.

Nice to see it fits in the platform! Wouldn't suprise me if they managed to foul something at this point .

Also good to know they seemingly can get to the bay and back to gabalfa on battery.

 

[John R]

Nice to see it fits in the platform! Wouldn't suprise me if they managed to foul something at this point .

Also good to know they seemingly can get to the bay and back to gabalfa on battery.

Did it not shuttle back and fore to Queen St before heading back north back onto the wires? So much more than Gabalfa to the Bay and back?

 

[VR494]

Did it not shuttle back and fore to Queen St before heading back north back onto the wires? So much more than Gabalfa to the Bay and back?

The tests operated between Cardiff Bay to Radyr and back. A 6 car 398 is unable to be accommodated in platform 1 at Cardiff Queen street.

 

[Caaardiff]

Attached is a picture taken at Cardiff Bay during testing on Thursday last week, where a pair of 398’s underwent battery testing.

3Q41 formed of a pair of 398’s about to depart with a test train to Radyr.

Guessing you were there for it. Any information about how it went?

 

[VR494]

Guessing you were there for it. Any information about how it went?

Three unit diagrams initially from Taffs Well will need to be allocated. This will displace the 15X off the Bay work.

The team are confident to be in a position for a June launch, around WC 8th.

Driver training will most likely be starting shortly for the first cohort as well.

Realtime Trains | 3J00 0525 Taffs Well Depot to Cardiff Central | 08/06/2026

Real-time train running information for 3J00 0525 departure from Taffs Well Depot to Cardiff Central on 08/06/2026. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 3B00 0540 Taffs Well Depot to Cardiff Queen Street | 08/06/2026

Real-time train running information for 3B00 0540 departure from Taffs Well Depot to Cardiff Queen Street on 08/06/2026. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 3B02 0557 Taffs Well Depot to Pontypridd | 08/06/2026

Real-time train running information for 3B02 0557 departure from Taffs Well Depot to Pontypridd on 08/06/2026. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

 

[Caaardiff]

Three unit diagrams initially from Taffs Well will need to be allocated. This will displace the 15X off the Bay work.

The team are confident to be in a position for a June launch, around WC 8th.

Driver training will most likely be starting shortly for the first cohort as well.

So after all the drama and criticism created on here, they're actually more or less on track to enter service soon?

 

[VR494]

So after all the drama and criticism created on here, they're actually more or less on track to enter service soon?

I wouldn’t say that they are on track, the criticism is definitely warranted, and the date mentioned is just a target the team would like to achieve, with some political pressure added on.

There are still major problems with these units, and if the absence of tests today isn’t enough of a hint of how it’s going - I don’t know what else to say.

== Doublepost prevention - post automatically merged: 9 Apr 2026 ==

Update:

An unidentified 398 is reported to have suffered a superficial thermal runaway while under charge at Taffs Well. Due to nature of the incident, a full fleet inspection is now apparently necessary to ensure there are no underlying issues.
I’m not sure how this is going to affect the training currently ongoing, but there could be a possibility the BMS system has failed here, resulting in damage to the battery pack.

 

[John R]

To a layman, what exactly does a thermal runaway mean in practice.

 

[MikePJ]

It means that the battery becomes uncontrollably hot - energy contained within the battery gets released as heat. Sometimes this will start an actual fire, other times it just results in the battery overheating and being damaged.

In lithium batteries, thermal runaways can sometimes be caused by what's called "dendrite growth" - if the battery is not properly managed (in my line of work, this can include charging the battery at temperatures below freezing) then lithium metal particles can be deposited inside the battery in places where they shouldn't, and if they build up enough then they cause a short circuit and a thermal runaway.

 

[John R]

Thank you @MikePJ.

 

[Prime586]

Thermal runaways under charging can also be caused by the cells getting too hot during the charging process (which has been one of the causes of the troubles on the TfW 230s, as their battery rafts have no active thermal management - most EVs have air or liquid-cooled heat exchangers to maintain the optimum temperature for the cells during charging or discharging) or by overcharging of individual cells (multi-cell lithium packs usually use balance charging to monitor and equalise the voltage in each individual cell).

 

[VR494]

Just to give an update to you all. The fleet team think they have identified the issue of the recent thermal runaway episode, and are subsequently checking the units to see if this needs wider fix. Once the units are cleared, then the fault free test runs will be able to recommence. And there’s a lot of units to get through, 1,500 miles each!

There a great chance now that due to issues with the wires on the Cardiff Bay line being out of use, after failing the switch on, the tram-trains will be entering service between Treherbert and Cardiff Central firstly. And there’s a possibility these will break down and block the TAM as well. And cannot be recovered without a major operation involving two additional units.

There is one other big problem though, and I say this lightly, only around 4-6 units out of the whole delivery of 32, with one still at Old Derby appear to be in an operational state. The rest are to put it in layman’s terms, broken in various ways and cannot be used in their current form. The entire fleet near enough is out of action and in no fit state, thats only just been discovered, I’m not joking about that, seriously - it’s been covered up!

 

[Chris125]

There is one other big problem though, and I say this lightly, only around 4-6 units out of the whole delivery of 32, with one still at Old Derby appear to be in an operational state. The rest are to put it in layman’s terms, broken in various ways and cannot be used in their current form. The entire fleet near enough is out of action and in no fit state, thats only just been discovered, I’m not joking about that, seriously - it’s been covered up!

I'm surprised you seem surprised? Testing and training with a handful of operational units seems standard practice with new fleets, after all they don't need the whole fleet operational right now and won't for quite a while.

 

[VR494]

I'm surprised you seem surprised? Testing and training with a handful of operational units seems standard practice with new fleets, after all they don't need the whole fleet operational right now and won't for quite a while.

Despite the issues previously mentioned, it’s only just becoming apparent the true scale of this. The test track runs, telling union members the fleet was in a position to begin training when it clearly is not! Forget the yellow fronts, even the instructors on the course are rejecting the concept. No one wants to touch the things.

 

[Caaardiff]

Isn't there only a requirement of 2-4 units to start the cardiff bay service anyway?
Whats the issue with the wires? Thought it was a successful launch that TFW promoted?

 

[MikePJ]

The 398 recovery issue does make me wonder if TfW should be looking to acquire a diesel rescue vehicle (either a small loco or a road-rail shunter) to assist dead 398s in an emergency.

== Doublepost prevention - post automatically merged: 11 Apr 2026 ==

Isn't there only a requirement of 2-4 units to start the cardiff bay service anyway?
Whats the issue with the wires? Thought it was a successful launch that TFW promoted?

Yeah, the press release contained a note saying that the overhead line was tested but tests revealed some remedial work needed doing before it can be left energised. I cycle past it most days and the switchgear at Butetown still has temporary earthing straps on it, so it’s definitely not energised.

 

[Cardiff123]

There is one other big problem though, and I say this lightly, only around 4-6 units out of the whole delivery of 32, with one still at Old Derby appear to be in an operational state. The rest are to put it in layman’s terms, broken in various ways and cannot be used in their current form. The entire fleet near enough is out of action and in no fit state, thats only just been discovered, I’m not joking about that, seriously - it’s been covered up!

If this is all true, then of course it's been covered up, as we have an election looming, and the governing party is publicly in denial about the scale of their predicted losses.
Hopefully the new Welsh Government will be honest about the scale of the problems with the 398s, especially as if 150s do return in numbers to the Pontypridd lines, that will need to be explained to the public.

The first appearance by James Price after the election in front the Senedd Committee that deals with transport & infrastructure will be interesting to watch.

 

[Dai Corner]

If only a few of the 398s are in good running order, it begs the question of why aren't the rest? Stadler have a reputation as a quality manufacturer, I thought? Is it because they've been sat in the depot doing nothing for up to three years? If so, did nobody foresee that that would be a problem and postpone delivery? Or was the spec incorrect or not adhered to and nobody noticed until recently and get started on the required modifications?

 

[VR494]

If this is all true, then of course it's been covered up, as we have an election looming, and the governing party is publicly in denial about the scale of their predicted losses.
Hopefully the new Welsh Government will be honest about the scale of the problems with the 398s, especially as if 150s do return in numbers to the Pontypridd lines, that will need to be explained to the public.

The first appearance by James Price after the election in front the Senedd Committee that deals with transport & infrastructure will be interesting to watch.

It’s not fair on the staff at all though, these things are not in any kind of fit state, or ready to be used. They are throwing up serious faults, buttons pressed for key systems, and the units doing other things it shouldn’t - I’ll leave that one up to you to work out what I mean. A rushed training package, which looks like the union has been held over the table and forced to agree, just to get them out! It’s been reported, the atmosphere there at the moment is not good at all. And the attitude is, you wanted the wages, deal with it.

== Doublepost prevention - post automatically merged: 11 Apr 2026 ==

If only a few of the 398s are in good running order, it begs the question of why aren't the rest? Stadler have a reputation as a quality manufacturer, I thought? Is it because they've been sat in the depot doing nothing for up to three years? If so, did nobody foresee that that would be a problem and postpone delivery? Or was the spec incorrect or not adhered to and nobody noticed until recently and get started on the required modifications?

What was originally ordered was incompatible from day one. To compare, a bathroom designer at a major store like Wickes, says to you that you can have a walk in shower, you pay the cash, and then the fitter says otherwise. The buyer has no experience or knowledge of the industry so parts cash. They are totally incompatible with the setup. Apparently the ones used in europe, such as Germany maybe be different levels of spec and are operated by different companies, DB just for rail etc, but all come under the same brand identity or livery. But still look like a tram-tram. These are designed for street running with a little on heavy rail under dispensation, and need a full electrical supply system to work properly.

 

[Caaardiff]

A rushed training package, which looks like the union has been held over the table and forced to agree, just to get them out!

Given the power and influence of the Railway unions, I'm very surprised by this.

When the 153's were brought in from GWR and EMR there was a huge fuss about the seats and they weren't used until they were replaced, as one example. If the 398's aren't ready to be used efficiently, then I can't see any union being held over any tables.

TFW need to bite the bullet and admit the plans were wrong. Use them on Cardiff Bay shuttles, Coryton - Penarth and Cityline, even Caerphilly - Cardiff where they are best suited and get more 756s in for the TAM. Save any spare 398's for when/if crossrail expansion happens.

 

[35B]

What was originally ordered was incompatible from day one. To compare, a bathroom designer at a major store like Wicks, says to you that you can have a walk in shower, you pay the cash, and then the fitter says otherwise. The buyer has no experience or knowledge of the industry so parts cash.

Then the buyer needs to ensure that they have the expert advice to make the right decision - and follow it. Unlike one of us going to (say) Wickes, there’s no sale of goods act - commercial buyers (which includes governments) are expected to have the ability to procure the right advice.

 

[craigybagel]

Given the power and influence of the Railway unions, I'm very surprised by this.

When the 153's were brought in from GWR and EMR there was a huge fuss about the seats and they weren't used until they were replaced, as one example. If the 398's aren't ready to be used efficiently, then I can't see any union being held over any tables.

It would be very surprising IF it's actually true. That's a very important caveat.

 

[LNW-GW Joint]

Where do Keolis-Amey fit in all this?
Aren't they the technical consultants and project managers for the procurement and introduction of the 398s?

 

[positron]

Keolis-Amey were the ones responsible for the spec and procurement of the new fleet, then it all got nationalised so they don't have to deal with the consequences. Keolis stepped away because they don't really care about the infrastructure side, and Amey are left doing infrastructure but I don't know if that includes fleet introductions I think they're just responsible for the actual hardware. So the bay line not working I think is Amey's problem, but the 398s being scrap metal I think is outside of their responsibility now.

 

[LNW-GW Joint]

Keolis-Amey were the ones responsible for the spec and procurement of the new fleet, then it all got nationalised so they don't have to deal with the consequences. Keolis stepped away because they don't really care about the infrastructure side, and Amey are left doing infrastructure but I don't know if that includes fleet introductions I think they're just responsible for the actual hardware. So the bay line not working I think is Amey's problem, but the 398s being scrap metal I think is outside of their responsibility now.

My understanding is that K-A were retained as the Metro infrastructure and rolling stock introduction specialist/PM, leaving TfW Rail as the TOC operator.
Happy to be corrected if that's not the current setup.
The main point is I think TfW is not the only organisation responsible for the late introduction of the class 398 fleet, along with Stadler of course.

 

[VR494]

It would be very surprising IF it's actually true. That's a very important caveat.

Company council have signed off the training package for drivers, despite there being loads of concerns. They didn’t even communicate this with other reps apparently until it was late in the day. Now the DI’s are in despair and pushing back on the content due to issues.
They’ve been thrown under the bus, and it will now be the DI’s who will be responsible for marking off each trainee on the traction regardless, no management involvement.

== Doublepost prevention - post automatically merged: 11 Apr 2026 ==

The 398 recovery issue does make me wonder if TfW should be looking to acquire a diesel rescue vehicle (either a small loco or a road-rail shunter) to assist dead 398s in an emergency.

They were looking for a coupler to attach to the 15x to assist them, the tractor unit on Taffs well is just for shunning them around.

I’m glad I’ve retired, it’s not going to be the same anymore.

== Doublepost prevention - post automatically merged: 11 Apr 2026 ==

My understanding is that K-A were retained as the Metro infrastructure and rolling stock introduction specialist/PM, leaving TfW Rail as the TOC operator.
Happy to be corrected if that's not the current setup.
The main point is I think TfW is not the only organisation responsible for the late introduction of the class 398 fleet, along with Stadler of course.

Stadler apparently just plug in a computer and reset the software to clear the faults. They are under no obligation to do anything I believe, and everything is paid for on an additional fee. Fitters cannot touch them.

Keolis left during covid, they wanted to have a Manchester metrolink of South Wales.

Amey don’t really have the capacity or capital to match the network rail system, and most of the work seemed to be tendered out to local trades at the lowest price.

 

[craigybagel]

I’m glad I’ve retired, it’s not going to be the same anymore.

== Doublepost prevention - post automatically merged: 11 Apr 2026 ==

This explains a lot.

I stand by my previous comments and see no reason to believe things are anywhere near as bad as you claim. But time will tell I'm sure.

 

[VR494]

This explains a lot.

I stand by my previous comments and see no reason to believe things are anywhere near as bad as you claim. But time will tell I'm sure.

Yes, I’ve paid enough brass and been lucky enough to escape these 398’s. I have no doubt the mainline will be the next target for the reforms coming soon as well.

People moaned about Arriva, they were a lot more organised and no doubt would have done a better job of this had they not pulled out.

 

[Dai Corner]

Keolis left during covid, they wanted to have a Manchester metrolink of South Wales.

Keolis were contracted to provide what the franchise agreement specified. The Welsh Government nationalised the franchise, which would have gone bankrupt if it had continued because of the covid lockdowns and collapse in revenue. The staff were transferred to the new Government owned operators Transport for Wales Rail Ltd.

Did all the managers and engineers who knew what they were doing and specified the 398s subsequently leave Tfw Rail and take their expertise with them?