Two heat-related derailments in two days put Network Rail's track spending under scrutiny

Two passenger train derailments caused by track buckles occurred on consecutive days — 13 and 14 August 2026 — injuring 20 people at Lewes and marking the first heat-related buckle derailments to harm passengers in Britain since Motherwell in June 1986, forty years earlier.

Data from the past decade frames the significance. Britain has recorded around 23 passenger train derailments in 10 years, an average of just over two a year, of which five resulted in injuries and two in fatalities. Track defects caused five of these, or 22% of the total. Three were slow-speed derailments on wide gauge track. The remaining two — the buckle-related incidents at Lewes and Wickford — happened on consecutive days this August.

What happened at Lewes?

At around 15:54 on 13 August, a train formed of two four-car Class 387 electric multiple units derailed 1.6 km north of Lewes station. The rear three vehicles derailed and overturned, coming to rest on their sides.

Around 150 people were on board. Twenty required hospital treatment, some for serious injuries. There were no fatalities, but the train and infrastructure sustained significant damage.

Preliminary analysis of On-Train Data Recorder data from the front vehicle shows the train was travelling at around 65 mph (105 km/h) approaching the point of derailment. The driver applied the brakes as the train passed that point, and it had begun to decelerate.

RAIB inspectors observed wheel-climb marks on the rails. CCTV from the derailed train and a previous train showed a track geometry irregularity before the derailment point, with indications of recent nearby track maintenance. RAIB had also received several reports of rough riding at the location from passengers on other trains.

Weather was a key factor. The derailment occurred in hot, sunny, still conditions at around 27°C ambient, during a sustained period of hot and dry weather. The embankment at the site consists of clay sitting on loose deposits of clay, silt, sand and gravel — layers sensitive to moisture variation. Inspectors saw no evidence of a significant embankment slip, but found evidence of some previous movement. RAIB published its initial report on 19 August.

What happened at Wickford?

At around 14:08 on 14 August, a train formed of two five-car Class 720 EMUs travelling at 124 km/h derailed 3.4 km south-east of Wickford station. Only the rear vehicle derailed. Its wheels ran on sleepers and ballast for around 2.4 km. The train stayed upright, and none of the estimated 62 people on board was injured.

The driver reported seeing a kink in the track which rocked the driving cab; forward-facing CCTV confirmed track misalignment at the point of derailment. The driver was reporting the defect when an emergency call arrived from a train passing in the opposite direction, whose driver had seen ballast flying from beneath the derailed vehicle. The derailed train's driver then braked.

The track, signalling and overhead electrification equipment suffered significant damage, and the passing train received minor damage from flying ballast. This information also appeared in RAIB's 19 August initial report.

Why do buckles matter now?

Until July, derailments from track kinks or buckles were extremely rare. The last one causing passenger injuries was at Motherwell in June 1986, where the buckle occurred between two sets of points laid in cold weather and never restressed.

The temperature record explains the timing. The four hottest summers up to 2024 were separated by just 0.05°C. Then 2025 beat the previous record by 0.34°C, and 2026 beat that by another 0.40°C — a 0.74°C rise in the record across two summers. This year saw temperatures of 30°C or more on 40 days, against the previous record of 34 days set in 1995.

Network Rail's own figures quantify the operational cost. Heat accounted for 646,000 delay minutes in 2022/23, with a further 498,000 from summer embankment shrinkage followed by autumn rainfall; storms accounted for 1.3 million delay minutes in 2023/24. The 2024 Climate Change Adaptation Plan (CCAP) notes cold and snow impacts are reducing while flooding, heat and subsidence impacts increase. The CCAP's Integrated Climate Change Risk Assessment rates temperature among the highest risk categories.

How is CWR managed?

Continuous Welded Rail, progressively replacing jointed track from the mid-1960s, is fixed firmly to the track structure — concrete sleepers in ballast with shoulders preventing lateral movement, though wooden sleepers remain under some S&C and bridges. Jointed track, by contrast, needed 5mm expansion gaps at 176 fishplates per mile.

CWR management depends on the stress-free temperature (SFT) of 27°C, which balances compression at high temperatures against tension at low temperatures, controlling buckle and rail-break risk. Rails laid below SFT are stretched before welding — a 300-metre rail laid at 11°C needs 55mm of stretch.

Each region maintains a critical rail temperature (CRT) register per CWR section: 56°C for track in perfect condition, reduced for factors such as wooden sleepers, poor ballast shoulders and adjacent construction. On hot days, rail temperatures can run 20°C above ambient air.

What did the Oakervee review find?

The Extreme Heat Taskforce report led by Sir Douglas Oakervee, published in 2023, found 23 buckles were reported in 2022, 13 of them on two consecutive days of extreme heat. Eighteen were at sites not on the CRT register; 15 were at or within 100 metres of S&C.

Heat alone does not cause buckles. The report listed contributing factors including ballast condition and profiles, drainage, sleeper condition, track clips and pads, transition zones at bridges and level crossings, wooden S&C bearers with shallow switches, and low SFT.

Its 25 recommendations covered record keeping, learning lessons from the 23 buckles, a programme to remove risk at low CRT sites, detailed inspections of S&C above 60 mph, competency reviews, consistent hot weather preparedness, and a policy of zero unmitigated track buckles. It also suggested raising SFT to 30°C if broken-rail risk in cold weather can be sufficiently mitigated.

What happens next?

Within hours of the Wickford derailment, Transport Secretary Heidi Alexander spoke to senior officials at Network Rail and the Office of Rail and Road to ask whether blanket action was needed; no such action followed, reflecting existing extreme heat mitigations.

RAIB's investigations will examine the effectiveness of hot weather mitigation measures, track condition and maintenance at both sites, the actions of those involved, the Lewes embankment, and weather conditions on the day and in preceding weeks and months — in effect testing whether the CCAP and Oakervee measures work.

At a 19 August press briefing, Rail Minister Lord Hendy said it is "quite clear that there is significant climate change". He noted Network Rail's CP7 (2024-2029) climate resilience spending on earthworks and drainage is five times CP6 levels, expressed no doubt that CP8 will increase extreme weather funding, and said the industry must await RAIB's findings.

The funding split invites scrutiny. Of the £2.8 billion allocated to climate resilience projects in CP7, 78% goes to drainage and earthworks and only 2% to track. Whether RAIB's recommendations force a significant increase in track expenditure in CP8 is now the open question.