Network Rail will slow trains down and change timetables on several routes across England from 3 August 2026. The cause is drought — the ground beneath the tracks is drying out and becoming unstable. South Western Railway is expected to announce similar measures soon, as its West of England line is seen as especially at risk The Guardian.

Here is why this happens. Much of Britain's railway sits on clay soil. When clay loses water — which it has, because spring rainfall was unusually low and the summer has been hot and dry — it shrinks. As the soil shrinks, the ground underneath the tracks can shift, and the beams holding the rails (called sleepers) may drop or move out of place. That creates cracks and uneven track. National Rail says trains cannot run at full speed over damaged track, so speed limits are put in place National Rail. Network Rail also says slowing trains reduces strain on overhead power lines and helps prevent further damage Network Rail.

A simple way to picture it: imagine a house built on clay. During a drought, the clay beneath the foundation dries and contracts, and the house may crack or shift. The same thing happens to railway tracks.

The UK is now in its fourth heatwave of 2026, as of late July.

The routes affected include Great Northern services in Cambridgeshire and Norfolk, Greater Anglia and c2c services in Essex, and the eastern end of the Elizabeth line. Great Northern has announced timetable changes from 3 August 2026 on its line to and from King's Lynn. Greater Anglia plans to alter some evening Essex services and run replacement buses. Some late c2c services to Shoeburyness will change, and the Elizabeth line will run fewer trains between Gidea Park and Shenfield from 11pm to midnight on certain dates The Guardian.

South Western Railway's West of England line, which runs from London to Exeter, Salisbury, and Yeovil, is particularly exposed. The stretch between Salisbury and Exeter is mostly single-track — meaning only one train can use it at a time in each direction. So when a speed limit slows one train down, the trains behind it are stuck waiting. In the worst cases of hot weather, trains can be slowed to as little as 5 mph, according to SWR's own guidance South Western Railway.

This is not the first time. SWR introduced similar speed limits and timetable changes in summer 2025 after another dry spring and summer. In June 2026, during an extreme heatwave, SWR changed its timetable and told customers to only travel if essential on 24, 25, and 26 June Devon County Council. Network Rail separately urged passengers in extreme heat zones to only travel if absolutely necessary during that record heatwave Network Rail Media Centre. In May 2026, Network Rail reported rail temperatures above 50°C, noting that such heat can cause rails to bend or buckle, which also forces trains to slow down Network Rail Facebook.

To fix the problem, Network Rail uses machines called tampers. These lift the track and push crushed stone — known as ballast — underneath to create a solid base. In 2025, engineers treated about 62 miles (100 km) of track in the Anglia region this way. Network Rail expected to use 49,000 tonnes of ballast across 2026 to keep tracks stable before and during summer The Guardian.

The broader context here is how often these measures are now needed. The Guardian links the ongoing drought to the climate crisis. When the same kind of disruption recurs year after year, when thousands of tonnes of stone are needed to shore up tracks, and when multiple heatwaves hit within a single summer, it suggests the railway system is facing a long-term challenge — not a one-off problem. Single-track sections like Salisbury-to-Exeter make things worse, because delays spread through the network with no alternative routes available.

SWR has a public webpage explaining how dry soil leads to speed restrictions, delays, and disruption on its network South Western Railway. The Telegraph and the BBC also reported that SWR was expected to announce its own speed and timetable changes soon The Guardian.