Image copyright Stadler Image caption Brand new trains are due to come into use on the line in 2023

Transport for Wales (TfW) has said it is looking at options for seating on one line after concerns new trains would cut capacity.

It plans to use larger, refurbished trains on the Rhymney line in 2020, followed by brand new ones in 2023.

But figures suggest services run by the new trains will have less capacity than the refurbished ones, and in some cases even less than current trains.

TfW said it was "constantly" reviewing its plans.

It plans to temporarily replace the current Pacer trains on the line with refurbished Class 769 trains.

The figures, obtained through a Freedom of Information request, show a large increase in seating on services with the Class 769 trains, only for that to go down again on the Rhymney line's Bargoed and Penarth routes when the new Stadler Flirt trains arrive.

James Price, the chief executive of TfW, has told Assembly Members it was working to ensure there was no drop off in seats once the new trains are introduced.

Projected peak hour total train seating capacity 2019 to 2023

In 2018 KeolisAmey won a £5bn bid to run rail services in Wales and the new South Wales Metro for 15 years.

That contract is overseen by Transport for Wales, an arm of the Welsh Government.

The figures, obtained by a member of the public, show seating capacity at three stages:

for 2019 with the current Pacer trains

for 2022 when the line will be operated by Class 769s

for 2023 when the line will be operated by Stadler Flirts

The projections suggest that at peak evening time on the Penarth line, between 16:00 and 18:15, the number of seats will rise from 1,526 in 2019 to 2,312 in 2022, before falling back to 1,269 in 2023.

That would be a drop of nearly 17% on the new trains compared with the current ones.

At the same time of day, seating capacity between Bargoed and Caerphilly is projected to rise from 1,716 in 2019 to 2,601 in 2022, then fall again to 1,701 in 2023.

Image copyright Welsh Government Image caption The Metro promises a faster, more integrated network of trains, buses and light rail services

Mr Price told an assembly committee last week that officials were working on ensuring capacity grows when the new trains are in place.

He said the temporary trains were "huge in comparison to what we have seen before".

"What we need to look at now is how we make sure that grows when the new rolling stock comes in as part of the Metro," he said.

Mr Price told AMs there was a risk that "the number of seats drops by two or three, compared to the 769s".

"We are working on that now to ensure that does not happen," he said.

'Underestimated'

During the meeting, Mr Price said the Wales and Borders franchise assumed a 65% rise in capacity in five years when it was awarded to KeolisAmey.

But he said with the "climate change emergency, with things like a potential congestion charge" the potential growth in passengers had been "underestimated".

Image copyright Transport for Wales Image caption Class 769s are due to come into service later this year

Plaid Cymru South Wales East AM Delyth Jewell said: "While the Welsh Government may argue that there will be a general increase in capacity in 2023, Transport for Wales' own figures show that passengers on the Rhymney line will actually see a reduction in capacity during peak periods at this time.

"There could very well be a greater increase in demand than Transport for Wales is preparing for as more and more people start commuting to Cardiff over the next few years, which risks repeating the mistakes of the previous franchise under Arriva.

"My fear is that a reduction in capacity in 2023, combined with a big increase in demand, has the potential to cause further misery for long-suffering Rhymney line passengers."

She said she was glad TfW had "committed to reviewing the situation".

Caerphilly Labour AM Hefin David said: "I'm in regular contact with Transport for Wales and the commitment they have made to meet the challenge of suppressed demand has occurred directly as a result of the representations I've made to them.

"I use the line myself at peak time and it is clear that the increased capacity we will see this year must be maintained when the new trains are in service."

'Constantly reviewing'

A Transport for Wales spokesman said: "We're aware of concerns regarding future capacity on the Rhymney line.

"However, we are currently fully reviewing all our passenger number forecasts and the service we provide in 2023 will meet those demands, as many options are being planned and considered."

The spokesman added services were "continuously changing and we are therefore constantly reviewing our plan".