Why are so many trains in France cancelled during heatwaves?

French state rail operator SNCF has been making headlines during the current historic heatwave by preemptively cancelling services. 

Dozens of trains have been cancelled since the start of the heatwave last week, including local TER trains, high-speed TGVs (InOui and OuiGo) as well as Intercités trains (also comprising complete cancellations of overnight services). 

In the capital Île-de-France region, around 10% of all commuter rail trains have been cancelled until further notice, with calls to work from home where possible to avoid overcrowding on trains.

It has not stopped incidents of broken down trains along the nation’s rail network during the heatwave however, including a TGV stuck for several hours near Dijon where passengers complained of a lack of water, toilets, and roasting temperatures inside carriages. 

On the whole however, the network’s caution has minimised the risk of mass issues for passengers, and the head of the SNCF Jean Castex has made pleas for vulnerable travellers to avoid using trains until the heatwave subsides. 

Why are trains impacted? 

The rail network is one of the public services facing the brunt of the heatwave, affected by several factors. 

The largest of these is the impact of the heat on rail infrastructure, notably rolling stock, overhead lines, and on rails themselves. 

While France’s rolling stock of trains are being slowly modernised, several lines rely on trains that in some cases date back to the 1970s. 

These older trains exist without the modcons that make travelling in hot weather bearable (no aircon, potentially no plug sockets, etc), and were made in an era where it was almost unthinkable that temperatures in France could surpass 40C for several days on end. 

These carriages were built not to withstand such high temperatures, and travelling out in the blazing sun they function as an oven, getting increasingly warm inside with little way for heat to escape.

As night-time temperatures remain well above average for the season, the carriages do not cool down naturally, meaning temperatures are already extremely warm before passengers have even begun to board the first service of the day.

Another issue is that on electrified lines (just over half of the nation’s routes are electrified, with these routes accounting for 85% of overall traffic), overhead cables can sag in excessive heat. 

Trains run the risk of colliding with cables, leading to accidents and delays. Trains must therefore drive slower than usual to avoid these objects, or in extreme cases journeys must be cancelled until temperatures drop.

The most prevalent issue however is the impact of hot weather on the rails themselves. 

Steel rails can be significantly hotter to touch than recorded temperatures – in some cases around 60C – causing them to expand and curve as they push up against other sections of track – a process known as ‘buckling’. 

This threatens trains running along the route with derailing, leading trains to run slower or being altogether cancelled as a precaution against major accidents.

The duration of the current heatwave alongside hot night-time temperatures means rails are not cooling down overnight, making the issue more impactful the longer the heatwave lasts.

Why are there cancellations in France? 

During periods of heatwave and subsequent cancellations, passengers can get frustrated particularly if they still have to travel on the network and see their journeys impacted. 

They point to other, hotter countries in Africa and Asia, where temperatures are considerably warmer than in France but trains are less impacted by the weather.

The first thing to point out is that it is not only France’s rail network that is impacted during these periods of intense heat, many other European countries are also affected. 

The UK, Spain, Germany, Italy, and several others all cancel services during intense heatwaves. 

The fact of the matter is rail infrastructure in these nations are not equipped to deal with intense heat because it has historically not been an issue. 

In comparison, railways in countries that are consistently warmer than Europe use special materials to allow trains to run in hot weather, in turn sacrificing the ability for trains to run in cooler conditions.

European networks are themselves adapted to run in colder winter conditions that would bring services in warmer countries to a standstill.

In many of these warm countries, high-speed rail services at the level found in Europe – dozens of routes travelling at 320km/h – are not in place, as trains cannot run this fast in the heat even with modifications to deal with high temperatures. 

Rail lines are often unelectrified too, reducing the impact of sagging cables but making trains slower and polluting. 

Rail operators ultimately have to make a trade-off between accounting for climate extremes – with Europe traditionally preparing networks for cooler weather – and the ability to run high-speed services while adhering to budgetary constraints. 

As heatwaves become more common and more intense in Europe, rail infrastructure may need to be adapted for hotter temperatures. 

This will not come without intensive works lasting several years and impacting the busiest routes in France, and costing billions of euros – measures that may be too difficult for authorities to swallow. 

Short-term solutions include painting rails white which can reduce the temperature by up to 10C. The UK and Italy already have these measures in place. 

To carry this out across France’s network and on the busiest routes without interrupting services would be a major challenge however.