Watch: Rail boss says Transport for Wales must make sure tragic crash is never repeated

James Price, chief executive of Transport for Wales, was speaking after the collision near Talerddig in Mid Wales, at 7.26pm on Monday.

One man in his 60s died from a heart attack, while 15 people needed hospital treatment, four of them having suffered "serious" injuries.

Accident investigators are working to find out why the trains – one bound for Shrewsbury and one headed for Aberystwyth – crashed.

There have been suggestions the incident was caused by 'slippery rails' with Transport for Wales running services at reduced speed today because of the same issue.

In a video posted reacting to the tragedy Mr Price said: "I'd like to express my sympathy for the family and friends of the gentleman who sadly lost his life in the incident yesterday.

"I'd also like to express my sympathy and thanks to the customers we were carrying who have been injured, or who were otherwise involved in the incident.

"I'd like to express my sympathy for our staff who were injured and I would also like to thank the emergency services who worked very hard in difficult circumstances yesterday to help everyone that they possibly could, and who are still on site today.

"What is important now is that we understand exactly what caused this incident, so that we can make sure nothing like it happens again.

"The police will now work with the RAIB (Rail Accident Investigation Branch), and the ORR (Office of Rail and Road) to ensure that we full understand what happened and then we will make sure that we deal with any of those issues, as I said so anything like this cannot happen again."

Meanwhile Marie Daly, chief customer and culture officer at Transport for Wales, added: "I'd like to take the opportunity to thank our customers who over the last few days have seen delays and cancellations across our network due to the significant incident that happened on Monday evening.

"We are doing all we can to make sure our customers and our colleagues who were involved are as supported as possible and we are working with investigators to make sure we can get the line in Mid Wales open as soon as possible."

It comes as the RAIB said the condition of the track on the approach to the collision point meant "adhesion" between wheels and rails was "relatively low".

It said this suggested an Aberystwyth-bound train may have slid while braking, causing it to crash at a speed of around 15mph into a stationary train destined for Shrewsbury.

TfW said today its services were running at a reduced speed across large parts of its network "due to slippery rails".

Routes affected include between Wrexham General and Bidston, between Swansea and Shrewsbury, between Llandudno Junction and Blaenau Ffestiniog, between Tenby and Pembroke Dock, between Holyhead and Llandudno Junction, and between Frodsham and Chester.

Monday's crash happened on the Cambrian line in a rural location with a single track, close to a passing loop where trains travelling in opposite directions can pass each other.

Network Rail said one of its railhead treatment trains – which tackle autumn leaf fall – ran along the line where the crash occurred and the passing loop on Sunday night.

An internal log of what happened during the crash shows the driver of the train for Aberystwyth reported they entered the loop as planned but were "unable to stop due to the railhead conditions", causing the train to pass a stop signal.

A signaller instructed the oncoming train to perform an "immediate stop", but a collision could not be avoided.

A conductor on the train that slid sustained a "bang to the head" and "possible broken arm", while the driver of the other train suffered "bleeding" and was initially trapped in their cab because it was damaged.

The RAIB said it will publish a further update on its investigation "in the coming days" once it has gathered and analysed more evidence.

Leaves cause major disruption every autumn when they stick to damp rails and become compressed by train wheels.

This creates a smooth, slippery layer similar to black ice on roads, reducing trains' grip.

Speed restrictions are often imposed in an attempt to reduce accidents such as the crash between two trains outside a tunnel near Salisbury, Wiltshire, in October 2021 which left 13 passengers and one driver requiring hospital treatment.

A South Western Railway train slipped on crushed leaves, causing it to slide past a stop signal and smash into the side of a Great Western Railway service.

It is understood Network Rail has not made any immediate changes to how it deals with leaves on the line following the Mid Wales crash, and will await the outcome of the RAIB's investigation and any recommendations included in it.

The RAIB has not issued an urgent safety announcement, which it does when it believes rapid action is needed following an incident.