Train lines across the UK's rail network are at risk of buckling during periods of extreme heat. Steel rails expand as they get hotter, causing tension against neighbouring track pieces, which can lead to curving and buckling.
Network Rail states that most of the network can operate with track temperatures up to 46C, though rails have been recorded as high as 51C. If a rail buckles, lines must be closed for repairs before trains can resume.
Beyond buckling tracks, extreme heat 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. Heat stress can also cause hidden failures in signalling control, power supplies, and trackside telecoms.