Periods of extreme heat pose a risk to the UK's rail network as steel tracks can expand and buckle. Network Rail states that steel rails can absorb heat up to 20C hotter than the air temperature, with most of the network able to operate when track temperatures reach up to 46C.
When rails expand and there is no room for further expansion, they can buckle. This necessitates closing the line for repairs before trains can resume service, according to Network Rail. John Lawrence, chair of the Institution of Engineering and Technology Railway Technical Network, highlighted that track buckles and dewirements are significant concerns for engineers, bringing derailment risks.
Hot weather can also affect overhead power lines, which power approximately 44% of UK passenger trains. These lines can expand and sag, leading to temporary speed restrictions, delays, and cancellations. Lawrence also noted that heat stress can cause "hidden failures" in signalling control, power supplies, and trackside telecoms, alongside the risk of lineside fires.