South Western Railway is expected to announce reduced train speeds and timetable changes as prolonged drought conditions cause the soil beneath railway embankments to shrink, disturbing track alignment. This follows similar measures already confirmed by rail operators in the east of England, and reflects a wider pattern of the climate crisis increasingly disrupting Britain's railway infrastructure during hot, dry summers.

The disruption stems from "soil moisture deficit" caused by an unusually dry spring followed by summer heatwaves, which shrinks the clay soil in embankments and causes track sleepers to shift, forcing trains to slow down for safety. Network Rail has confirmed late-night speed restrictions and altered timetables from 3 August affecting Great Northern, Greater Anglia, c2c and the Elizabeth line, while SWR's West of England line, including the largely single-track Salisbury to Exeter section, is particularly vulnerable to knock-on delays. Engineers use tamping machines and ballast to stabilise the track, with about 62 miles treated last year and roughly 49,000 tonnes of ballast expected to be used across 2026.