RAIB issues remote monitoring sensor warning
03/02/2026
The Rail Accident Investigation Branch (RAIB) in the UK has issued urgent advice asking Network Rail to consider the risk of remote monitoring sensors on earthworks being overwhelmed during extreme weather and unable to send safety-critical alerts to control staff.The independent rail accident investigation body issued urgent safety advice on 19 December 2025 about the use of remote monitoring technology to verify the safety and integrity of railway earthworks.
The advice states that lineside monitoring equipment used on Network Rail infrastructure may not be able to detect slope failure in some circumstances. As a result, this equipment may not provide data as expected to support safety decision-making, particularly during extreme weather conditions.
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| Advice was issued following the derailment of an Avanti West Coast Class 390 Pendolino in November 2025, which resulted in injury to passengers and damage to the train and railway infrastructure Image courtesy of Mary and Angus Hogg (CC BY-SA 2.0) |
The advice has been issued as part of RAIB’s ongoing investigation into the derailment of an Avanti West Coast intercity passenger train at Shap in Cumbria on 3 November 2025. The train, formed of a Class 390 Pendolino tilting electric multiple unit (EMU), was travelling at around 134 km/h when it struck landslip debris that had been washed onto the track. This material lifted the first bogie off the rails and to the right, where it ran derailed for around 560 m.
There were nine staff and 86 passengers on board the train at the time of the collision. Four people were treated for minor injuries as a result of the accident and damage was caused to the train and to railway infrastructure.
RAIB said its investigation work so far had found that the landslip was caused by a period of heavy and sustained rainfall.
RAIB’s preliminary examination found that a drainage channel, which runs across the cutting slope above the washed-out material, was unable to accommodate the volume of water that was present. This led to the slope material below becoming saturated, initiating the landslip.
The cutting slope was fitted with remote monitoring equipment designed to detect ground movement. At the time of the accident, the monitoring equipment at Shap was recording data and reporting to its online monitoring service. However, it had not been formally entered into operational use, so it was not sending alerts to the Network Rail control centre. Similar equipment is operational on other parts of the railway infrastructure.
This type of equipment, when configured for Network Rail slope monitoring applications, is mounted on steel spikes every 2 m along the base of the slope. The position of the sensors is recorded at intervals.
Movement of the sensors is recorded by the monitoring system as four colour-coded levels of alert, of which the highest two are considered to represent significant movement:
- Green (information): movement of between 10 mm and 30 mm;
- Amber (major): movement of between 30 mm and 60 mm;
- Red (severe): movement of between 60 mm and 90 mm; and
- Black (critical): movement of more than 90 mm.
Around four hours before the accident, the sensors nearest to the landslip began to show minor movement of the earthwork, below the threshold needed to trigger a green alert. This movement continued for the next two hours, remaining below the green alert threshold.
The RAIB advice explained that at the time the evidence available suggests that the landslip occurred, the two sensors in the path of the debris were tipped over and subsumed by the material sliding down the slope. It would appear that this occurred too quickly for them to determine and transmit their movement and to generate an alert.
RAIB concluded that the wireless signal of the sensors was also unable to pass through the layer of material that covered them. This is based on their ability to re-establish a connection and report a variety of alert levels as the site was cleared.
The investigation body is advising Network Rail and other parties involved in UK railway infrastructure management to consider and, if necessary, mitigate this risk.
Remote condition monitoring equipment has emerged over recent years as an increasingly common means of verifying the health of railway assets and it is widely used on the UK network and internationally. Concomitantly, concern has grown over the threat to railway structures posed by the increasing incidence of extreme weather largely driven by climate change.
