Network Rail will impose late-night speed restrictions and altered timetables across multiple English routes from 3 August 2026, as persistent drought conditions destabilise clay-soil embankments. South Western Railway is expected to become the latest operator to announce similar measures, with its West of England line identified as particularly vulnerable The Guardian.

The restrictions respond to what engineers call a soil moisture deficit — a shortfall of water in the ground caused by unusually low spring rainfall followed by a hot, dry summer. The UK is entering its fourth heatwave of the year as of late July 2026. Clay soil in railway embankments shrinks during prolonged drought, reducing moisture volume and causing sleepers (the beams that hold the rails in place) to drop or shift. National Rail notes that trains cannot travel at full speed over cracks caused by drought, and that temporary speed restrictions are introduced in affected areas National Rail. Network Rail's hot-weather campaign page also states that restrictions minimise force on overhead power lines and reduce the risk of damage Network Rail.

Think of clay soil like a sponge: when it dries out, it contracts, and anything resting on top — in this case, railway track — loses its solid base. The effect is gradual but cumulative across a network, especially where tracks are shared or single-line.

Affected routes include those run by Great Northern in Cambridgeshire and Norfolk, Greater Anglia and c2c 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 introduce rail replacement buses. Some late c2c services to Shoeburyness are set to change, and the Elizabeth line will operate a reduced service between Gidea Park and Shenfield between 11pm and midnight on certain dates The Guardian.

SWR's West of England line, connecting London to Exeter St David's, Salisbury, and Yeovil, faces particular exposure to drought-related track problems. The Salisbury-to-Exeter section is predominantly single-track, meaning speed restrictions can cause cumulative delays across the network — when one train slows, others behind it have nowhere to go. In the most extreme hot-weather cases, trains are slowed to as little as 5 mph, according to SWR's public guidance South Western Railway.

SWR took comparable speed-restriction and timetable steps almost a year earlier, in summer 2025, in response to another dry spring and summer. Earlier in June 2026, during an extreme heatwave, SWR amended its timetable and advised customers to only travel if essential on 24, 25, and 26 June Devon County Council. Network Rail separately urged passengers travelling to, from, or within extreme heat zones to only travel if absolutely necessary during a record heatwave that month Network Rail Media Centre. In May 2026, Network Rail reported rail temperatures exceeding 50°C during a heatwave week, noting that this level of heat can cause rails to buckle, sometimes requiring trains to be slowed down Network Rail Facebook.

To address dried-out soil, Network Rail uses machines called tampers to lift track and push stone ballast — the layer of crushed rock beneath the rails — underneath, creating a solid foundation. In 2025, engineers treated about 62 miles (100 km) of track in the Anglia region using tampers. Network Rail expected to use 49,000 tonnes of ballast over the course of 2026 to help keep track smooth ahead of and during summer The Guardian.

The broader context here is the increasing frequency with which these measures are being deployed. The Guardian attributes the persistent drought conditions to the climate crisis. The recurrence of soil-moisture-deficit-driven disruptions in consecutive years, the scale of ballast deployment, and the compounding effect of multiple heatwaves within a single year point to a structural challenge for rail infrastructure. Single-track sections like Salisbury-to-Exeter amplify the operational impact, as delays cascade through the network with limited capacity for rerouting.

SWR maintains a dedicated public webpage explaining soil moisture deficit and how it causes speed restrictions, cumulative 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.