The UK's transport network is on high alert as a prolonged spell of extreme heat threatens to buckle railway tracks and weaken road surfaces. With temperatures set to soar in southern England, potentially reaching 38°C by the end of the week, experts warn that infrastructure could be pushed to its limits.
Professor Xueyu Geng, a Professor in Geotechnical Engineering at the University of Warwick, has highlighted the dangers posed by prolonged high temperatures on Britain's built environment. Buildings, often designed to retain heat, are finding their cooling systems stretched to breaking point. But it is the ground beneath our infrastructure that poses the most critical risk.
The railway network is particularly vulnerable, with steel rails expanding significantly in extreme heat – a 1°C rise causing approximately 11mm of expansion per kilometre. When temperatures exceed the 'stress-free' threshold for which the rails were installed, the track can buckle laterally, a phenomenon known as a 'sun kink'. Speed restrictions are imposed not just as a precaution but as a structural necessity to prevent catastrophic failure.
Road surfaces also face significant challenges in sustained high temperatures. The softening of bituminous asphalt causes rutting and deformation, affecting drainage and vehicle handling. However, the most insidious risk lies with earthwork embankments that support much of the UK's railway and road infrastructure.
These engineered soil structures rely on a delicate balance of soil moisture and root systems for stability. Prolonged extreme heat disrupts this balance by desiccating the soil, causing it to shrink and crack, while vegetation under stress dies back, losing its reinforcing root tension. This process gradually weakens the embankment without overt surface warnings.
The forecast is particularly concerning due to its sustained, multi-day nature, including 'tropical nights' where temperatures remain above 20°C, and unusually high humidity. The Met Office has also indicated that thunderstorms and intense rainfall are expected to follow as the heat breaks down, exacerbating the risks to weakened earthworks.
Source: University of Warwick, Professor Xueyu Geng