Transport for Wales (TfW) has announced it is temporarily pausing use of its new class 398 tram-trains after issues were identified during what the operator described as "passenger testing." The trains, supplied by Swiss manufacturer Stadler, were supposed to be ready for rollout last year but are still not fully operational.
Software Issues and Temporary Pause
A spokesman for TfW described the pause as temporary, stating that the issues identified were related to software. The operator added that these "teething issues" are common when new trains are being rolled out.
Three fully electric tram-trains had been running on the Pontypridd to Cardiff Bay line since this summer but have now been removed from the line while the issue is worked on. TfW said Stadler has developed a software update which is awaiting validation. All trains will then go through a testing process before they can return to service.
Rollout Delays and Future Plans
TfW has 36 of the class 398s, which were initially intended to be rolled out by the end of 2025. The operator has since said the tram-trains will be introduced in phases, with all expected to be in service by summer 2027. The trains are being introduced as part of the £1bn South Wales Metro Project, which is hoped to deliver "generational change" for customers in Cardiff and the South Wales Valleys.
Class 756 electric 'tri-mode' trains have been rolled out across the Core Valley Lines since late 2024 and remain in operation. Announcing the rollout of the class 756s, then-transport minister Ken Skates said they were part of an £800m investment in new trains for Wales. The class 398s are intended to replace the stock of 756s on the Core Valley Lines, with the tri-mode trains then being used elsewhere on the network.
Ongoing Disruption and Alternative Arrangements
The removal of the tram-trains from operation means there is ongoing disruption on services between Pontypridd and Cardiff Bay. The direct half-hourly service is no longer running from Pontypridd, Trefforest, Trefforest Estate, Taff Well, Radyr, Llandaf and Cathays as a result of the issue. Passengers can still get to Cardiff Bay by swapping trains at Cardiff Queen Street, where the old class 150 stock is currently being used for the Cardiff Queen Street to Cardiff Bay services.
A spokesman for TfW said the class 398 tram-trains are expected to return to service "in the next few weeks" after a software update has taken place. The full statement from Transport for Wales reads: "TfW is currently introducing brand new tram trains as part of the South Wales Metro which is delivering a generational change for customers in Cardiff and the South Wales Valleys. These new trains are in a period of passenger testing and we’re temporarily pausing their use while the train manufacturer Stadler works on software issues that have been identified as part of the testing process. These sorts of teething issues are common and part of the complex process of introducing new trains. The Class 398 is an innovative type of tram-train that will eventually be able to operate on street as well as on heavy rail lines. We have a plan in place to continue to deliver rail services on the Cardiff Bay line whilst our passenger testing takes place."
A Stadler spokesperson said: "We identified an issue during passenger testing of the Class 398 tram-train fleet and we’re working closely with Transport for Wales to address it. These are brand-new trains and it’s completely normal to identify minor issues when first being introduced to a network. Our investigation has confirmed a software issue, which we’re now in the process of updating. We’ll continue working closely with Transport for Wales to complete the necessary validation and testing before the fleet returns to service."
