While they may not always run perfectly to time, every day thousands of people use Welsh railways with little to no fanfare. Even during temperate whether, there are dozens of reasons why trains might be cancelled – urgent repairs are sometimes needed, there could be an emergency incident or there may not be enough staff.
However, thousands of people in south Wales found out just how much the weather can affect the railway when two lines were brought to a complete standstill because of the heat.
Transport for Wales (TfW) was forced to cancel all services to Merthyr Tydfil and Aberdare north of Pontypridd for over two days. A problem was first identified on Friday evening (July 11), leading to the cancellation of all services on Saturday, July 12.
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It was Wales’ hottest day of the year so far, with 33 degree temperatures recorded in Cardiff.
The disruption continued for the entirety of Sunday, when rail replacement buses were arranged to transport passengers between Pontypridd and Merthyr Tydfil and Aberdare.
TfW said the heat had caused a “track defect” at Abercynon, forcing the railway to close until repairs were completed. Get the latest Ponty news first by signing up to our newsletter here
The railway remained so hot that repairs couldn’t be undertaken until temperatures cooled down overnight on Sunday.
The problem caused chaos for the thousands of fans trying to travel to and from the Stereophonics’ gig at the Principality Stadium on Saturday. Due to the number of people TfW was expecting travel by rail to the gigs, it took the decision to issue a “do not travel” alert for the Aberdare and Merthyr lines.
Railway lines across the UK are often brought to a standstill in the extreme heat, whereas European countries’ railways often seem able to withstand the temperatures. Here is why trains are cancelled during heatwaves in the UK:
Why does hot weather bring trains to a standstill?
Network Rail said that hot summers could be as challenging for railways as freezing winters as the heat could affect the rails, overhead power lines as well as the ground the track sits on.
The main problem caused by heat is buckled rail. The steel rail on a railway track is a long piece of metal which absorbs heat easily, meaning that the track can get up to 20 degrees hotter than the air temperature.
Network Rail explained: “When steel gets hot it expands. The rails become longer and start pushing against the pieces of track next to them. This can damage the equipment that detects where trains are keeping them a safe distance apart. When this happens, we stop trains to keep everyone safe. If there is no room for the rail to expand, the rail can buckle and we need to close the line to fix it before trains can run again.”
As to whether mitigating measures could be put in place, Network Rail added: “The variations in short-term weather and long-term climate mean that it is neither practical nor cost-effective to implement these measures permanently on the British rail network.”
Most of the network can operate when track temperatures hit up to 46°C, according to Network Rail. This is the equivalent to an air temperature of around 30°C.
However, the temperature creeped above this figure over the weekend.
What happened to the railway at Abercynon?
Transport for Wales has issued an update elaborating on the issue that occurred on the railway over the weekend. It has explained that the reason why the lines were closed for a lengthy period was because the railway was so hot that repairs couldn’t be carried out.
An update on its website reads:
“A track defect emerged between Pontypridd and Abercynon just before 7pm on Friday, 11 July.
“We quickly had engineers on site who assessed the situation and deemed that a repair could not go ahead owing to the exceptionally high track temperature we were experiencing (52 degrees on the metal rails). This was because at those temperatures metal can expand and as such a repair couldn’t take place.
“The damage itself was due to an issue with the track bed that meant a small section had to be repaired. Once it emerged we could not effect a repair that evening, we agreed ticket acceptance with local bus companies and also sought to put replacement buses in place.
“This meant no trains could operate on the Aberdare or Merthyr lines. The Treherbert line was still able to run. Unfortunately, the situation continued into Saturday due to the high temperatures. On the Saturday it proved impossible to provide sufficient rail replacement services north of Pontypridd, however ticket acceptance remained in place on local bus routes.
“Given the limitations of this and the expected numbers traveling for a major concert in Cardiff, we took the decision to tell customers not to attempt to travel by train on the Aberdare and Merthyr lines.
“This situation continued into Sunday. As temperatures cooled on Sunday night, we were able to successfully repair the defect ready for Monday morning start up.”
They added: “We’re incredibly sorry for the disruption this caused you, especially if you were planning to travel in for work or the concert. What should have been a straightforward repair was made more complex by the heat we were experiencing.”
Will anything be done to prevent the heat causing problems to the railway in future?
Transport for Wales said it would hold a cross industry review into the incident “to take any learning we can from the incident to ensure we are best able to adapt to infrastructure problems during extreme weather in future”.
Jenifer Baxter, boss of Industry Wales, a Welsh government-owned organisation which advises on the development of economic policy and planning, told BBC Radio Wales’ Sunday Supplement: “There are things that we can’t do anything about. The reaction of metal to extreme heat is one of those areas, and there are other countries around Europe who have managed to come up with ways to solve these problems.”
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