Rail staff have admitted that many of them are "dreading" new toilet-free Valleys tram-trains being put into service.

Part of the new South Wales Metro network – an ambitious multi-million-pound transport upgrade project expected to reach fruition in 2023 – the electrified tram trains will greatly increase service frequency and shorten journey time to and from the likes of Aberdare, Treherbert, and Merthyr Tydfil, known as the Core Valleys Lines.

However Transport for Wales has said that in order to "create a modern Metro-style service" options were limited when it came to utilising "vehicles with fully accessible toilets on board."

Read more: First look at what the trains will look like on the new South Wales Metro line

That means anyone who gets caught short while using the service would have to disembark to use the facilities on the station platform before catching the next train along.

And despite the same being true of other UK tram and light rail networks, such as in Manchester or the London Underground, it's something certain TfW employees see as a potential problem.

"The drivers and conductors are gobsmacked and dreading the day these trains are put into service," said one staff member, who did not wish to be named.

"The lack of toilets is something that's going to become an issue. If someone elderly needs to go, or there are families with small children onboard, are they really expected to get off with all their belongings and then catch the train behind?

"And what about Friday and Saturday nights, for example, when passengers have been enjoying themselves at the pub beforehand? I’m sure you can guess what problems are likely to arise from the lack of onboard loos in that instance."

The concerns have been echoed by the National Union of Rail, Maritime and Transport Workers (RMT) which said risk assessments into the situation needed to be made.

Initially First Minister Mark Drakeford claimed the new rail services would have "up-to-date" facilities including toilets, Welsh Government having taken control of Transport for Wales Rail in late 2020. But it was later revealed that this would not be the case.

That led to the likes of former Plaid Cymru leader Leanne Wood questioning how those needing to visit the toilet frequently, such as pregnant women or those with medical conditions, would cope.

"It is unreasonable to expect people to get off the train to go to toilet and catch the next service," she said at the time.

"Are people fully aware of the implications of the new train franchise when it comes to a lack of toilet facilities on trains? I suspect most people are not and will not be supportive of it."

However a Transport for Wales spokesman played down the issue. "We recognise the importance of accessible toilet facilities for passengers using future Metro services," he said, explaining that while other destinations on the new network would have onboard toilets the type of train needed in the Valleys dictated otherwise.

"We are creating a modern metro-style service with tram-trains which need the ability to run on street – thereby facilitating future extensions of the Metro network.

"As such there are limited options available amongst global rolling stock for these types of vehicles with fully accessible toilets on board."

He added that TfW are also increasing the number of "universal access toilets" at stations on the Metro network.

"That means passengers will never be more than 20 minutes away from a toilet with a 'turn up and go' frequency of services allowing people to hop on and off at their convenience.

"We'll continue to work with colleagues, stakeholders, customers, and accessibility groups to ensure their voices are heard as we develop our services."

To get the latest email updates from WalesOnline click here.