How are rail infrastructure managers dealing with extreme heat in Europe?

Combating climate change is one of the major challenges of the 21st century. Extreme weather phenomena such as heat waves and floods are becoming increasingly common. This is forcing infrastructure managers to adapt to this new reality. What are some of the tactics employed to mitigate the impact of extreme heat on railways in Europe? SNCF, Adif, Network Rail, SBB, and DB share their methods with RailTech.

By its very nature, railway networks are exposed to all kinds of weather. Because of its design rules, the track is intrinsically quite resilient to high temperatures: high-speed trains run well in countries with warmer climates than Europe, such as Morocco. However, rails in direct sunlight can be up to 20°C hotter than the air temperature. As a result, the temperature of the rails can reach 60°C when the air temperature is approaching 40°C. As the rails are made of steel, they can expand as they get hotter and can start to bend – this is known as “buckling”. There is also a risk that the catenary wire, which has to be perfectly straight to work properly, will relax. Furthermore, vegetation on or near tracks can also catch fire in certain cases, halting traffic and damaging infrastructure.

“This summer there has not been any issue where heat or drought impacted rail operations in Spain,” according to an Adif spokesperson. Nevertheless, the Spanish railway infrastructure manager has developed a calculation tool, in order to “evaluate the risk areas according to the forecast temperature and the neutralisation temperature (when the rail tensions are non-existent).” This tool is used to calculate the critical environmental temperature from which there is a high risk of deformation of the track due to lateral buckling. This way it is possible to establish temporary speed limits in those sections where the weather forecast predicts very high temperatures. The tool is already operational, but Adif says it will continue to focus on its improvement to increase accuracy and usability.

In France, SNCF Réseau has been using a prediction tool called Metigate, since 2021. It provides 13-day minimum and maximum rail temperature forecasts and 3-day air temperature forecasts. These data points are available from around 180 sites across the entire national network. With this tool, rail temperature forecasts are no longer based solely on air temperature forecasts but rather integrate meteorological parameters such as cloud cover, sunshine, humidity and more so predictions are more accurate. SNCF Réseau uses these forecasts to organise and adapt monitoring during the hot season and any heat wave periods.

British railway manager Network Rail procures weather advice from the private weather service provider MetDesk Ltd through a standard commercial process. While this approach offers economic benefits, it has drawbacks as the services are fixed based on conditions during procurement and do not reflect potential scientific or technological advancements during the contract period. MetDesk sources its services from observational and forecast data acquired from prominent producers like the Met Office and ECMWF. Their forecasts rely on deterministic ECMWF global forecasts at 12-kilometre resolution and lack direct integration of probabilistic details in weather warnings. MetDesk also generates a precipitation nowcast utilising Met Office radar-derived data that has been refined and interpolated. They incorporate various data sources like satellites and river level gauges, to offer customised weather products to Network Rail. The current weather forecast management involves Extreme Weather Action Teleconferences (EWATs) to communicate weather alerts and decisions through a complex decision tree to ensure safety.

In addition to weather forecasting, railway managers also increasingly monitor the condition of the tracks. In France, the rail network is subject to continuous close monitoring and regular maintenance in both summer and winter, according to an SNCF Réseau spokesperson. “Specific rounds of maintenance teams are deployed to monitor the infrastructure and anticipate issues. In the event of a fault with the installations, the staff are ready to intervene and take the appropriate safety measures”, they stated. In the same way as the infrastructure components, the track bed is checked regularly. The pressure exerted by the expansion of the rails on the engineering structures and any movements caused by the shrinkage of the embankments in the event of prolonged drought is monitored in minute detail by sensors capable of indicating any disorders.

Deutsche Bahn has installed temperature sensors in interlockings that are particularly relevant for operations, which automatically trigger messages if certain threshold values are exceeded, and is currently testing additional temperature sensors on rails and in level crossing interlockings, with remote monitoring via the central diagnostic platform DIANA. According to DB, “DIANA stands for ‘Diagnosis and Analysis’ and represents a web-based platform on which all diagnostic data can be integrated, interlinked, evaluated and visualised.” It is crucial to predictive maintenance in Germany. Furthermore, technical and awareness-raising measures are also applied to make track systems even more robust in the event of heat waves, through ground surveys or special inspections of sensitive infrastructure components.

In the UK, Network Rail remotely monitors equipment at key sites and receives a signal when infrastructure is beginning to overheat. “This allows us to send teams out to precise locations to predict and prevent infrastructure failures, limiting the time they have to spend on track,” says a spokesperson. Network Rail has also started using drones with thermal-imaging cameras to show when infrastructure is overheating. This helps reduce staff time on track so they can pinpoint potential issues and fix them before they cause delays. Using lineside monitoring equipment on embankments and cuttings also helps predict and prevent failures.

Innovative strategies are being employed to counter extreme temperatures and maintain rail efficiency. One effective method involves painting rail tracks white, a practice adopted by Network Rail and Adif. By coating rails with white paint, the temperature absorbed by the rails can be reduced by 5 to 10 degrees Celsius according to Network Rail. However, according to SBB, “Painting the rails white is expensive and has a number of disadvantages. For line inspectors, for example, it is much more difficult to detect any cracks in the rail. What’s more, one of the advantages diminishes as the paint gets dirtier. Studies carried out by SBB, DB and ÖBB show that painting the rails a light colour reduces their temperature by around 5 degrees. The industry agrees that this is not significant enough to be considered an effective preventive measure.”

SNCF has adapted its track laying and maintenance practices with enhanced safety margins. The modernisation process includes the implementation of design rules that bolster track resilience. Long welded rails are now being utilised, which effectively absorb temperature-induced stresses. Similarly, DB employs strategic temperature management by welding tracks at 23 degrees Celsius. This approach enables the track to absorb fluctuations in temperature, ranging from minus 20 degrees to plus 60 degrees. SBB notes that modern rail welding techniques have greatly reduced the number of buckled tracks: “Over the entire SBB network, an average of only three to seven track misalignments are recorded and corrected each year.”

Additionally, lines without long welded rails receive specific maintenance attention. Also, when temperature standards are surpassed, SNCF Réseau may reduce train speed or even halt traffic. “The risk of track deformation can be reduced by using concrete instead of wooden sleepers. SBB is already using more of these. These concrete sleepers can better absorb transverse forces: They better absorb the pressure caused by the metal of the rails expanding when exposed to heat. Cooling by water from water tankers is also an efficient measure to prevent rail deformation and is used in particularly exposed areas, for old tracks or after maintenance work,” shared an SBB spokesperson.

Adif takes proactive measures during summer to identify areas lacking sufficient ballast, which can lead to lateral buckling. Innovative anti-buckling sleepers have been introduced in sections of the metric track gauge network to prevent such issues. SNCF Réseau ensures vegetation control throughout the year, reducing the risk of fire or trees interfering with tracks. In cases of vegetation fires close to tracks, SNCF Réseau may opt to reduce train speed or even halt traffic temporarily.

In various locations, overhead lines are being “weather-proofed” to prevent sagging. For instance, Network Rail has recently implemented this on the West Coast mainline, enhancing the overall reliability of the rail network.

To prevent heat-related failures of the control and safety technology, Deutsche Bahn has equipped thousands of facilities with air-conditioning systems. These are regularly maintained, checked and modernised. In addition, the railway company has installed temperature sensors in interlockings that are particularly relevant for operations, which automatically trigger messages if certain threshold values are exceeded. In this way, air-conditioning systems can be checked at an early stage before a malfunction can occur. SBB also has air conditioners in their signal boxes to prevent heat-induced system failures.

For its train operations, DB is investing in new vehicles for both long-distance and regional transport. By 2030, they will invest approximately 12 billion euros solely in new long-distance trains. These new vehicles come equipped with more powerful air-conditioning systems designed to withstand temperatures up to 45 degrees Celsius. The upcoming summer will see a 20 per cent increase in the number of ICE and Intercity trains compared to 2022, totalling more than 215 vehicles, all equipped with the latest robust air-conditioning technology. On average, three new ICEs will be added each month this year. The new air-conditioning systems not only enhance efficiency but also ensure high reliability with a 99 per cent availability rate.

Both long-distance and regional air-conditioning systems undergo thorough checks every six months. Intensive maintenance and technical overhauls are carried out as needed, including cleaning, replacing filter mats, and refreshing refrigerants and components. These maintenance efforts require annual expenditures in the tens of millions for both types of transport. Train attendants are well-versed in handling air-conditioning systems and receive regular training. In case of breakdowns, onboard staff swiftly transfer passengers to other carriages. Long-distance trains are equipped with ample water supplies totalling 65,000 litres across the fleet, with additional reserves at major stations. SNCF is also preparing its future TGVs for the heat waves of the future. Current trains are designed for maximum temperatures of 40°C. The TGV M, due in 2024, will be designed to adapt to the expected rise in temperatures over the coming decades.

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