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Rail is the first mode of transportation to have to fight two battles at the same time: decarbonize our transportation systems while adapting to the consequences of climate change. This is the paradox revealed by the heat wave currently affecting France. While the train is one of our best allies in the face of the climate emergency, it is also one of its first victims.
The slowdowns observed in recent days do not mean that the rail system is “down”: they are the result of a network designed for yesterday’s climate but now facing tomorrow’s climate. Why do trains slow down when the temperature reaches 40 °C? How is the rail system already adapting to heat waves, floods, and wildfires? And why is the solution certainly not to replace trains with planes, but rather to invest in a more resilient network? Let’s take a closer look.
With every heat wave, the same controversy resurfaces: Why do trains slow down when it gets very hot? And along with it comes this common misconception: that the French rail system is unable to withstand high temperatures.
In reality, when a train slows down during a heat wave, it’s not because the rail system is malfunctioning, but because safety doesn’t compromise with the laws of physics.
Contrary to what one might think, it is not the air temperature that is the determining factor, but rather the temperature of the infrastructure. In direct sunlight, a steel rail can exceed 60 °C, even when the thermometer reads “only” 40 °C. Like any metallic material, steel expands when heated.
On the French rail network, most main tracks are equipped with long welded rails (LRS). During installation, these rails are set to a release temperature—that is, a reference temperature at which mechanical stresses remain in equilibrium. When the gaps become very large, these stresses increase and, in the most extreme cases, the rail can deform: this is what engineers call buckling.
Although this phenomenon remains rare, the risk is serious enough to warrant preventive measures. And one of the main preventive measures is to temporarily reduce train speeds. By reducing the forces exerted on the track, these limitations help ensure the highest level of safety.
The heat doesn't just put a strain on the railroad tracks. The overhead wires that power electric trains also expand as temperatures rise. Air-conditioning systems on rolling stock are under greater strain, while certain signaling and infrastructure equipment requires closer monitoring.
The rail network operates as a single system in which the tracks, power supply, signaling, and trains must all function in a coordinated manner. When a heat wave puts strain on several of these components at the same time, operational measures may be implemented to maintain the regularity of service, but above all to ensure the safety of train operations.
These speed limits are therefore preventive: they are specifically designed to prevent incidents from occurring. In other words, the slowdowns observed during heat waves do not indicate a lack of reliability on the part of the train. Above all, they serve as a reminder of one reality: The climate is changing faster today than the pace at which rail infrastructure can be adapted.
That is where the paradox lies: while rail is expected to play a central role in the ecological transition, it must now adapt its infrastructure to a climate that is changing faster than anticipated.
Fortunately, however, this adaptation is no longer a thing of the future. Across France, the rail industry is already testing solutions to make its infrastructure more resilient to heat waves, floods, and hail.
The slowdowns observed during heat waves are, after all, just the tip of the iceberg. Because the real challenge lies elsewhere: How can we prepare the rail network for the consequences of a climate that is already changing?
For a long time, major developments in rail transportation have mainly focused on running more trains at higher speeds, while improving their energy efficiency and passenger comfort. Today, a new challenge has emerged: strengthen the rail system's resilience to extreme weather events. Longer and more frequent heat waves, droughts, floods, hail, wildfires… Climate projections predict warming of up to +4 °C by 2100 in France, accompanied by more intense weather events. These are all phenomena that rail infrastructure will now have to contend with.
Two strategies for addressing climate change are often contrasted: mitigation and adaptation. The first involves reducing greenhouse gas emissions to limit the extent of global warming. The second aims to prepare our infrastructure for the consequences of a climate that is already changing.
The rail industry is now one of the few sectors where these two battles are being fought on two fronts. On the one hand, it is expected to replace some of the travel currently done by car or plane with a mode of transportation that emits far fewer greenhouse gases, while continually improving its energy efficiency. On the other hand, it must adapt its tracks, maintenance centers, buildings, and equipment—as well as its organizational structure and operating conditions—in order to remain efficient despite increasingly extreme weather events.
For a long time, improving rail transportation mainly meant increasing capacity, speed, or energy efficiency. Now, a new criterion has emerged: resilience.
Every new project must now take into account the impacts of climate change from the very beginning of the design process: extreme heat waves, droughts, floods, hail, and wildfires. In other words, it is no longer just a matter of building a more efficient grid. We must also build a grid capable of continuing to operate under more challenging climate conditions.
This development marks a true paradigm shift. Adaptability is no longer a secondary concern; it has become a key criterion in how we design, operate, and modernize the rail system. And, fortunately, this transformation is already well underway.
How the Rail Industry Is Already Preparing for the Climate of Tomorrow
The good news is that this transformation is no longer a thing of the future. Across France, the rail sector is already implementing concrete solutions to make its infrastructure more resilient to extreme weather events, while continuing its efforts to reduce its environmental footprint.
Adaptation begins where trains are maintained. At its technical centers, SNCF Voyageurs is gradually identifying the sites most exposed to climate risks using the OCARA method (Cartographic Tool for Adaptation Risk Analysis). The goal: to better anticipate vulnerabilities and prioritize investments.
This approach is already being put into practice through very concrete actions: the installation of hail-resistant roofs, flood protection measures, improvements to the thermal comfort of buildings through the use of white-painted roofs, and the protection of outdoor spaces.
Adaptation also involves better resource management, including the installation of solar-powered shade structures and the recycling of water used during maintenance operations. A sign that this approach is now here to stay: 100% of SNCF Voyageurs’ new projects now incorporate climate change adaptation criteria.
Mitigating climate change and adapting to it often go hand in hand. This is particularly true for eco-driving, a practice that is now widespread among drivers. By adapting their driving to the road's profile, they can save up to 10% energy, while minimizing wear and tear on the equipment and improving passenger comfort.
Another example: a short story aerodynamic bow is gradually being installed on double-decker TGV trains. By reducing air resistance, it helps lower energy consumption while improving the front end’s resistance to minor impacts. Ultimately, SNCF Voyageurs estimates that this innovation could prevent the emission of 537 metric tons of CO₂ per year and generate nearly €560,000 in energy savings.
Preserving water resources is also a major challenge. In particular, the technical centers are testing a solution for exterior dry cleaning TGV trains, capable of reducing the water consumption required for this operation by more than 80%, while limiting water discharges into the environment.
Adaptation isn’t just about infrastructure. Heat waves also affect the thousands of employees who ensure the maintenance, traffic control, and operation of trains every day. To better protect its teams, SNCF Voyageurs is gradually rolling out cooling personal protective equipment for staff working outdoors or in maintenance centers during heat waves.
At the same time, initiatives such as the Heat Wave Plan help improve information and support for travelers when weather conditions disrupt traffic. After all, sustainable transportation isn’t just about low CO₂ emissions—it’s also about being able to continue operating under the best possible conditions, despite weather challenges.
In conclusion, the traffic delays observed during this heat wave can be frustrating. But above all, they remind us that climate change is already having very direct consequences on our daily lives: it is transforming the infrastructure on which our mobility depends.
In recent days, some media outlets have occasionally presented air travel as an alternative to trains slowed down by the heat. This interpretation completely misses the point. If trains are running more slowly today, it is precisely because they are already suffering the consequences of climate change—to which the aviation industry contributes significantly. For an equivalent journey, a flight emits dozens of times more CO₂ per passenger than a trip on the TGV. Replacing one with the other would therefore amount to addressing the consequences while simultaneously exacerbating some of the causes.
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The real answer? Investing in a rail network capable of withstanding the heat waves, floods, wildfires, and droughts that will characterize the coming decades. Because trains remain, by far, our best ally in decarbonizing transportation. And now more than ever, the best solutions to climate change deserve the resources they need to adapt.
The question, then, is no longer whether the rail system will be able to withstand the heat waves of the future. The question is whether we will give it the means to continue serving as the backbone of low-carbon mobility…
Psst… At HOORAY!, the entire team is convinced that the simpler, more accessible, and more enjoyable the train is, the more it will become the obvious choice. That is the whole point of our application and exclusive benefits offered to members of the HOURRAIL Club! : To help you travel more easily—and farther and farther—without flying. Find all the details here:
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The HOURRAIL Club: the community for low-carbon travel and slow travel
Issue du monde de la communication et des médias, Sophie est Responsable éditoriale chez HOURRAIL ! depuis août 2024. Elle est notamment derrière le contenu éditorial du site ainsi que La Locomissive (de l'inspiration voyage bas carbone et des bons plans, un jeudi sur deux, gratuitement dans ta boîte mail !).
Convaincue que les changements d’habitude passent par la transformation de nos imaginaires, elle s’attache à montrer qu’il est possible de voyager autrement, de manière plus consciente, plus lente et plus joyeuse. Son objectif : rendre le slow travel accessible à toutes et tous, à travers des astuces, des décryptages et surtout, de nouveaux récits.
