Persistent drought conditions caused by the climate crisis are expected to cause further disruption to trains across southern England, as the lack of rainfall affects the ground supporting railway embankments.
South Western Railway is expected to become the latest large rail company to announce timetable changes and reduced speeds to cope with the effects of hot and dry weather, after operators in the east of England said they were going to take similar steps.
Network Rail said last week that late-night speed restrictions and altered timetables would need to come into effect from 3 August “until the ground conditions have recovered”. Routes affected include those run by Great Northern in Cambridgeshire and Norfolk, by Greater Anglia and c2c in Essex, and the eastern end of the Elizabeth line from London.
The moves are in response to “soil moisture deficit” (SMD) caused by spring’s unusually low rainfall followed by hot, dry summer weather as the UK enters its fourth heatwave of the year.
Many sections of Britain’s railway network are built on embankments containing clay soil, which normally contains a lot of water. Long periods of drought reduce the volume of moisture in the soil, causing it to shrink, which in turn disturbs the ground that tracks are built on, causing sleepers to drop or move out of position.
Even relatively small changes in track geometry – the positioning, alignment and measurements of the line – mean trains must reduce their speed to run safely.
SWR is expected to announce its own speed and timetable changes soon, the Telegraph and BBC reported, almost a year after the rail operator took similar steps in response to another dry spring and summer.
Its West of England line, which connects London to destinations including Exeter St David’s in Devon, Salisbury in Wiltshire and Yeovil in Somerset, is particularly vulnerable to the problem.
And because the line between Salisbury and Exeter is a predominantly single-track railway, speed restrictions can cause cumulative delays, with a knock-on impact on other services across the network.
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Last week, Great Northern announced timetable changes from 3 August on the Great Northern line to and from King’s Lynn in Norfolk. Greater Anglia will alter some evening Essex services including rail replacement buses, some late c2c services to Shoeburyness will change, and the Elizabeth line will operate a reduced 11pm to midnight service between Gidea Park and Shenfield on certain dates.
Network Rail said its engineers reduce the effects of dried-out soil by using machines called tampers to lift the track, push stone ballast underneath and create a solid foundation so that trains can run smoothly. New ballast is also put down to help raise the level of the track.
Last year, engineers treated about 62 miles (100km) of track on Anglia routes using tampers to help tackle the effects of dried-out soil. In the run-up to summer, teams have already dropped thousands of tonnes of ballast to help keep the track as smooth as possible, with 49,000 expected to be used over the course of 2026.
