VE-I-6: Weather-related disruptions to the railway infrastructure

2021 stands out due to numerous disruptions to the railway infrastructure caused by weather events and weather-related patterns, not just in comparison to the low figures recorded in the pandemic year of 2020. In that year, winter storm Tristan caused massive disruptions to railway traffic due to freezing rain, snowfall and snowdrifts. In 2018 and 2019, the summer heat caused a noticeable number of disruptions. A trend analysis is not yet possible for the short time series.

Climate change impacts on the railway infrastructure

Just under 9 % of passenger transport and approximately 19 % of goods transport (expressed in passenger and tonne-kilometres respectively) as recorded in the pre-crisis year 2019, make railway transport an important building block of Germany’s transport system. On one hand, the railway entities are themselves keen on safeguarding largely disruption-free railway operations, and on the other hand, enterprises and passengers who use railway services for their logistics and mobility depend on punctual and disruption-free train services.

The weather and weather patterns rank among the important factors which can cause disruptions to the railway infrastructure and to railway transport, if they counteract the concept of ‘normal’ operations. As part of an analysis of climate change, the disruption scenario was explored by the Potsdam Institute for Climate Research (PIK) on behalf of the Deutsche Bahn company. The outcomes show that, in future, Germany’s railway infrastructure will be exposed increasingly to extreme and more intensive weather events, and that in the past, heat, heavy rain and storm were often the cause of repeated reports of disruptions.^{171 171}

Heat can affect the railway infrastructure, for instance in cases when it causes the failure of electronic circuit components or actuation and switch point surveillance systems. Heavy or persistent rain can, as demonstrated graphically by the disasters in the Ahr and Erft valleys in 2021, trigger floodwater waves inundating railway lines which run through valleys and if they are located in the vicinity of river beds thus underwashing railway tracks as well as affecting embankments and track beds. In cases where railway lines run along steep embankments, such precipitations can trigger landslides, ordinary mudslides or mudslides coming down from high mountains, which damage or completely destroy the transport infrastructures and control systems.

The indicator is based on data emanating from the disruption database maintained by the DB Netz AG. This shows the proportion of disruptions related to the weather and weather patterns in the company’s railway infrastructure covering all disruptions recorded by DB. In this context, disruptions are understood as events resulting in trains being late or cancelled. The disruption database serves for capturing disruption events occurring in the railway infrastructure as well as stating their primary cause. The disruptions are covered in the indicator according to one of six distinct cause categories: ‘lightning’, ‘heat’, ‘embankment fire’, ‘vegetation’, ‘winter’ as well as ‘railway track underwashing’.

In the time series which as yet is rather short, the year 2021 stands out on account of its high number of disruptions due to wintry conditions. These are due to winter storm Tristan which brought very heavy falls of snow and snowdrifts: Overhead wires and switch points were iced up, trees threatened to fall on to overhead wires and on to tracks while snowdrifts made tracks impassable. In order to prevent trains from getting stuck somewhere on the track, the railway company provided numerous alternative connections and made available accommodation trains in railway stations for any passengers who were unable to make their onward journey on the same day. The impacts of floodwater in the Ahr and Erft valleys in that year are only partly reflected in the indicator, because trains deleted from train schedules are not recorded in the underlying disruption database in view of the long-term line closure.

Apart from a slightly below-average occurrence of extreme weather events, the negligible disruption incidence in 2020 can be accounted for by the reduced traffic volume during the Covid-19 pandemic. Given the overall reduced amount of travel, it is obvious that fewer train journeys were affected by extreme weather events and associated impacts. Any damage occurring due to weather effects was frequently remedied before causing any disruptions to train operations.

In 2018 and 2019, however, high temperatures were largely responsible for disruptions to the rail network. The heat contributed to disruptions by causing points and signals to overheat. Moreover, work scheduled for track sections had to be rescheduled, given that tracks are only allowed to be fitted or removed within specified temperature ranges in order to avoid putting too much pressure or tension on steel during seasonal temperature fluctuations. Additional cancellations were caused by embankment fires flaring up along railway lines owing to drought and heat. Likewise, technical defects in air conditioning equipment and other structural components can lead to heat-related train cancellations. However, these are not covered in the indicator concerned with the railway infrastructure.

Disruptions due to branches and trees falling on overhead wires or on to railway tracks owing to storm and strong wind (vegetation category), occurred in relatively consistent volumes in the years illustrated. In order to prevent disruptions due to windthrow, it is important to carry out adapted track maintenance which curbs the growth of trees and bushes in the vicinity of tracks.

As far as the future is concerned, the PIK analysis of climate impacts carried out for Deutsche Bahn shows that heat situations will occur more frequently and will become more intensive. Likewise, progressive climate change is expected to entail an increase in heavy rain events. With regard to strong wind and storm, there are uncertainties to what extent the frequency of their occurrence is likely to change. However, there is a potential for seasonal shifts causing more disturbances, for instance when storms occur more frequently in summer or autumn, striking trees when they are in full leaf. At the same time, distinctly wintry conditions are on the wane thus becoming less frequently the cause of disruptions, although individual extreme weather events may continue to occur.¹⁷²

In order to counteract the challenges to the infrastructure threatening to arise from climate change, the railway transport sector is already implementing a variety of measures. These include solutions at the level of planning and technical solutions, with the aim to minimise climate risks affecting restoration, extension and renewal of railway tracks or to raise the technical standards for components used in track switch operation mechanisms and switch points as well as air conditioning equipment. Likewise, adapted vegetation management along railway tracks to avoid windthrow and reducing the incidence of embankment fires, are also part of these measures.

^{171 Edenhofer O., Hoffmann P.: Analyse des Klimawandels für die Deutsche Bahn: Studie zur räumlichen Ausprägung in Deutschland. Pressekonferenz Klimastudie am 18. Juni 2021. Potsdam Institut für Klimafolgenforschung (Hg.). https://nachhaltigkeit.deutschebahn.com/06_Strategie/01_klimaschutz/Pik_Studie/Klimawandelanalyse_DB.pdf}

^{171 - PIK – Potsdam Institut für Klimafolgenforschung (Hg.) 2021: Klima-Studie für Deutsche Bahn wird Grundlage für Resilienz-Strategie des Konzerns. https://www.pik-potsdam.de/de/aktuelles/nachrichten/klima-studie-fuer-deutsche-bahn-wird-grundlage-fuer-resilienz-strategie-des-konzerns}

^{172 - Edenhofer & Hoffmann 2021, PIK (Hg,) 2021, cf. endnote no. 171}

VE-I-6: Weather-related disruptions to the railway infrastructure | Umweltbundesamt