The United Kingdom is in the midst of a record-breaking heatwave and its infrastructure is not coping so well, with rail lines expanding by as much as nine kilometres in the heat.
Britain recorded its highest-ever temperature of 40C on Tuesday, which scorched fields and damaged airport runways, melted roads and shut train tracks.
Commuters were stranded as the record temperatures closed some rail lines and others were run at low speeds due to concerns the rails would expand and buckle.
As Transport Secretary Grant Shapps conceded, much of Britain's road and rail infrastructure "is just not built for this temperature".
How does it all work?
The majority of rail track in Britain is made of conventional ballasted track which consists of sleepers and ballast stones used to hold the rails in place.
The steel rail can expand or contract significantly in the summer and winter, pushing and pulling the railway out of shape.
The movement of trains also generates forces onto the track. The higher the speed, the greater the force of a train.
When heat expansion adds to the pressure, British trains have to slow down to reduce the additional forces they are applying.
In some countries where the force from high temperatures cannot be contained by sleepers and ballast, they use a solid concrete slab to hold the rails in place.
But UK's Network Rail said slab track costs around four times as much to install as standard ballast track, which is used in only a few lines.
Why can't UK trains handle the heat?
British rails have a stress-free temperature of 27C— countries around the world decide on a median temperature based on their climate.
According to Network Rail, when air temperature reaches 30C, the temperature on the rail can be up to 20 degrees higher, and parts of the track cannot cope at those levels.
Network Rail — which owns and operates 30,000 kilometres of railway track, bridges and tunnels — said it was not practical or cost effective for it to adopt systems suited to higher temperatures, due to the rarity of extremely hot days in Britain.
It also said that rails stressed to the same degree as those in very hot countries could make them less resilient to low temperatures in the winter.
UK rail network expands by 9km
But this time temperatures passed 40C, smashing the previous UK high temperature record of 38.7C which was recorded in 2019.
Network Rail said the temperatures expanded every kilometre of rail by approximately 30cm.
By painting parts of the rails white so they absorbed less heat, analysing track stability in winter and making adjustments before the summer, the network said the rails were less likely to buckle.
National Rail said several train services would still be affected moving forward and advised commuters to only travel "if absolutely necessary".
Is Australia any better?
The stress-free rail temperature in Australia sits between 35 and 40C .
Queensland University of Technology's Professor Tommy Chan, who works in the School of Civil and Environmental Engineering, said Australia still experiences the same problems as the UK.
"Our daily thermal difference sometimes is much higher – take for example Port Hedland in Western Australia -- their night temperature is similar to Brisbane's but their day temperature could climb up to 30C," he said.
Professor Chan said a few degrees could cause "some problems" along rail networks, but there were "many solutions".
They include changes to slippers, the thickness and shape of ballast used and using optical fibre sensors in rail systems.
"The UK's rail system – not the technology – may be a little outdated."
How does Melbourne's rail fare?
It's common for train tracks in Australia to expand in summer and rail networks follow procedures to limit speed during extreme heat events.
Melbourne's Metro Train lines have electronic monitoring sensors that dynamically measure the track temperatures in real time and apply speed restrictions in certain sections.
Metro Trains said the technology effectively minimised disruptions to passengers.
"By using actual track temperature, rather than the forecast ambient temperature, speed restrictions can be targeted to heat-affected parts of the network only," it said.
"When the track temperature of a line reaches 55C or higher, the maximum speed limit is restricted to 80km/h on a particular line or section of track.
"On days where the ambient temperature is forecast to reach 42 degrees and above in Melbourne, the maximum speed limit is reduced to 70km/h across the entire Metro network."
Professor Chan, who co-authored a paper on the behaviour of rail tracks at low and elevated temperatures, buckling and mitigation, said rail issues will be more common due to climate change.
ABC/wires
