Increased risk of extreme heat to European roads and railways with global warming

This study aims to investigate the increased cost to European road and railway infrastructures due to an increase in extreme heat corresponding to four different global warming levels (GWL): 1.5 ◦C, 2 ◦C, 3 ◦C, and 4 ◦C. Extreme high temperatures adversely affect road pavements through increased levels of rutting, while railways have a greater propensity to buckle under extreme heat. The choice of transport construction materials and methods for such infrastructures are generally made assuming a static climate. In road pavement design, this reflects the choice of an asphalt binder to effectively expand and contract within a given temperature range. In railway design, a stress free temperature (a key determinant in preventing buckling) is set based on regional historical climatic conditions. Global warming and the expected rise in the frequency and intensity of hot spells will potentially place large stocks of road and rail infrastructure outside their built operating conditions. An ensemble of 11 regional climate projections forced by RCP4.5 and RCP8.5 are used to compute the increased level of risk to road and rail infrastructures using two dedicated models.

This study finds that under a 4 °C global warming level, increased levels of extreme heat in EU + UK cause annual transport O&M costs to rise by €4.8 billion, corresponding to an overall 6.9% rise compared to current values. Mitigating emissions to comply with a 1.5 °C, 2 °C, and 3 °C rise in global average temperature limits the increase to €0.9 billion, €1.3 billion, and €2.8 billion, corresponding to O&M increases of 1.3%, 1.5%, 4.1% respectively. Depending on the value of the stock, replacement costs, and maintenance cycles in a country, the increase in risk can be much stronger. To pre-emptively limit risk, EU + UK road pavement construction standards and railway stress free temperatures should be updated to account for future changes in temperatures.