Drought, fires, heat waves, floods… The year 2022 will have been marked by meteorological phenomena of rare intensity, destined to repeat themselves. And for many sectors, the consequences of climate change are particularly complex to anticipate and manage.
This is the case in the rail sector, and the problem has been taken into account so far within the SNCF. “The rail network is by nature exposed to all weather hazards. It is therefore maintained and operated by integrating a high requirement of resilience: even if impacts on traffic are noted, they are managed. In summer and winter, the network makes the “subject, continuously, to close monitoring and regular maintenance”, promises SNCF Réseau, the subsidiary of the company responsible for ensuring the proper functioning of the railway infrastructure.
Rails resistant to rising temperatures
First point of vigilance: the temperature of the rails. On the ground, the thermometer can climb at breakneck speed during episodes of high heat. And in the event of a heat wave, the steel that makes up the rails undergoes strong expansion. “With climate change, we are talking for France of a rise in temperature of 1, 2, 3 or 4 degrees, compared to an average temperature of 14 degrees. The SNCF estimates that if the temperature on the ground exceeds 57 degrees, it is no longer able to ensure the safe conditions for the TGVs to run. You know the effect of a one-day railway strike on the country. So imagine that of a traffic interruption for several days,” warns François Gemenne, co-author of the IPCC report.
But do not panic. “The rails we make have an operating range that can go from -50 to over 100 degrees. Even if there were several degrees of heating, there would be no impact and the rails would be able to transit trains without any problem”, assures Guillaume Beraud, freshly appointed, last February, director of the Ascoval steelworks in Saint-Saulve, now in the bosom of Saarstahl. 40% of the volume produced by this factory goes to the SNCF, after passing through the rolling mills of the German steelmaker to give their final shape to the rails that will fill the French network.
In reality, it is the structure around the rails that must be closely monitored, in particular the sleepers which absorb the effects of the expansion of the rails. “Technological developments on the catenaries and actions on their adjustment also make it possible to reduce the risk of relaxation. The lines which do not include long welded rails are the subject of additional specific maintenance”, specifies SNCF Réseau. In 2019, the national ground temperature record was recorded in the vicinity of Nîmes with 64.7 degrees. With our Belgian neighbours, the 62 degree mark has been crossed.
In Switzerland, the rail network manager invests more than 25 million euros every year to prevent the consequences of climate change. “The Swiss Federal Railways strives to put in place structures that can withstand the stress generated by the heat only thanks to the rail fixings and the sleepers anchored in the ballast and the ground. If this is not enough, the rails are cooled by means of water drawn from tank wagons. This method is used in particularly exposed places, on old tracks or after maintenance work”, specifies Sabine Baumgartner, the company’s spokesperson.
The summer of 2022 has demonstrated this again, high temperatures also considerably increase the frequency of fires. On this point, the SNCF excels. “It could be a real subject, but she is very careful about the clearing around the tracks. Campaigns have been organized regularly for a long time and they work very well”, says Cloé Chevron, consultant and co-author of the report of the Climate Action Network for the recovery rail in France.
Flood risks closely monitored
At the SNCF, we are also scrutinizing very closely the risks of flooding on the rail network. The public company works in close collaboration with Météo France and its forecasters to anticipate as much as possible the risks of heavy rains and floods. A surveillance system, called TOUTATIS – Tournée Ouvrages en Terre sur Alertes Intempéries, notably enables maintenance workers to be warned when rainfall thresholds are exceeded. In 2021, the floods in Belgium, which a World Weather Attribution study has linked to the consequences of global warming, had a lasting effect on the country’s rail network. 25 sections of lines had to be interrupted, sometimes for periods of six to eight weeks, for damage approaching a total cost of 60 million euros.
The Belgian disaster served as an example at European and international level. Working groups between countries are regularly organized under the leadership of the International Union of Railways and the European Union to pool knowledge on the subject and plan for the future. “All infrastructure managers agree that water is the biggest problem for rail, with significant costs. We learn from each other and we are absolutely not competitors, but rather colleagues. Measures that have been proven in other countries, if they are adaptable to our conditions, are interesting to test”, explains Patricia Grobben, climate advisor at Infrabel, the Belgian railway infrastructure manager. .
The importance of data analysis
The SNCF thus necessarily looks at what is being done abroad. To lower the temperature of the rails, several European countries, including Switzerland, Belgium and Italy, have relied on the technique of white paint to try to bring down the mercury. A method that turns out to be ineffective. “The economic balance was not very positive. We gained a few degrees, but that didn’t represent much. Above all, it costs a lot of money, especially since you have to do it again almost every year. Finally, it there is a significant risk that the paint will make it difficult to detect cracks on the rail”, explains Annelies Van stevens, engineer specializing in tracks and switches at Infrabel.
To better prevent and anticipate the impacts of climate change, data management and analysis will be key. “It is essential to know the network better and to analyze the data that comes back more precisely. There are a whole host of IT tools that are currently being put in place to help analyze them, observes Lucile Ramackers, mobility expert at Capgemini Invent. The difficulty with SNCF Réseau is that everything is a priority. Deploying all these tools requires mobilizing resources which are also essential for maintaining the network. There is a real subject of arbitration”. The key is not to let your guard down and to keep a permanent watch. “The impacts of global warming are generally well managed and taken into account within the SNCF. On the other hand, the subject is constantly evolving. We must continue to invest and adjust the policy”, points out Cloé Chevron. After a sweltering 2022 summer, the 2023 season is likely to be another major test. The SNCF seems ready, but an extreme event cannot be ruled out.
