Last week, it was virtually impossible to take the train in the UK. Nearly all of the services on the National Rail network have reduced their service or posted “do not travel” warnings.
Transport for London, which runs the London underground and overground services, has also advised people not to travel. The service disruptions were due to the unprecedented heat wave sweeping across the UK and Europe, where the mercury peaked at 40°C in some towns and cities, breaking several records.
Yes, extreme heat does not always disrupt rail transportation as trains run through some of the hottest and inhospitable parts of the world, such as the Mojave and Sahara deserts.
These trains are able to cope with the extreme heat because it is not so much the temperature itself that causes issues but the difference between the actual temperature and the temperature the system was designed to handle.
Railways tracks and roads in the UK were not designed to handle such high temperatures, which they have been experiencing over the last week. Many European countries have opted to build infrastructure which can withstand extremely cold temperatures as this would more likely occur in that region. Now they have to deal with both hot and cold extremes, a genuine problem that won’t be easy, quick, or cheap to solve.
Vice reported that among the biggest concerns during extreme heat is buckling when the track is literally bent out of shape. Most train tracks these days are made up of long strips of steel called continuous welded rail (CWR).
These strips, which are welded together when installed, can often be miles long. CWR is popular because it is cheaper to maintain and provides a smoother, quieter ride than the traditional steel strips that gave trains the clickety-clack noise.
But an unfortunate unintended consequence is the long steel rails can make buckling more extreme.
Steel expands and contracts as the temperature changes. The longer the steel rail, the greater the force of that expansion and contraction. The railway sleepers are wooden boards laid across and underneath the tracks.
Under normal circumstances, the sleepers would keep the steel tracks in place during average temperature fluctuations. And ballast, usually crushed stones or gravel, gets packed underneath and between the sleepers to help keep everything stable.
Railroad engineers would use historic average temperatures to determine how much expansion and contraction the track is able to withstand before becoming unusable. This is something the railroad and the manufacturer decide on it before they put the rail in place.
The UK’s Office of Rail and Road found that in extreme heat, rail beds sitting in the sun all day will bake to around 10°C hotter than the air temperature, very much like the bonnet of a car left out in the sun in a South African summer.
When the steel rails expand due to the extreme heat, pressure is placed on the sleepers and ballast, which keep the rail line stable. Trains running over the tracks will add to that force, and the faster the trains go, the more force on the tracks, which is why most rail services in the UK are under slow speed warnings, if they’re running at all.
If the force becomes too much for the sleepers to handle, the tracks will buckle, become permanently damaged, and will need to be replaced. An expensive and time-consuming endeavour.
Due to extreme weather brought on by climate change, the rail network in the UK has become under severe pressure. Rails can typically only handle a certain range of temperatures on either extreme from the neutral temperature the rails were designed to accommodate.
If the UK undertakes the decades-long process of rating its network for hotter stress-free temperatures, it will make buckling in the winter more likely, according to Network Rail, which owns and maintains the country’s rail network. It will also cost hundreds of millions, if not billions of pounds, as studies have consistently found.
The Rail Network said that its engineers could design spaces for the concrete to expand into as they do with steel, but concrete can be four times more expensive than traditional ballast systems.
More frequent track inspections and temperature checks can help detect buckling before it takes place, but that is a necessary safety measure, not a means of maintaining full service during heat waves.
Currently, the UK and other countries experiencing frequent record temperatures are going to be stuck with infrastructure that simply cannot handle such extremes.
Grant Shapps, the UK’s transport secretary, told the media when questioned if the transport system could cope with extreme weather, he replied: “The simple answer at the moment is no.”
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