A new guidance document for periods of adverse and extreme rainfall will allow 'route operations controls to determine rainfall thresholds and the operating restrictions to the train service based on local conditions and knowledge'.
Network Rail said: 'Industry rules for reporting and reacting to heavy rainfall are being clarified and strengthened in September 2020. Supporting more consistent use of real-time rainfall data and application of extreme weather action teleconferences has already been addressed in refreshed company standards.'
The move was announced in an initial report from the national rail operator, which outlined the range of actions to prevent derailments as happened at Carmont near Stonehaven following heavy rains and landslides.
Actions include operating reforms and extra funding allocations, as well as taskforces looking into key areas around earthworks and weather monitoring.
An industry-wide group of stakeholders identified 'the need to strengthen industry rules providing instructions on train operation during extreme weather in the event of reports of water build-up and /or damage to structures above or below the railway'.
Network Rail confirmed it is publishing emergency changes within two existing National Operating Procedures and Weather Management Standards to cover the development of route operations control instructions.
Signallers have been reminded that reports of significant weather events, washouts and concerns that the ground or assets have become unstable means that 'all trains are stopped until the infrastructure is inspected by a competent engineer'.
'The emergency changes to our existing standards and procedures were published on 25 August 2020, with the new control guidance due to be published in September 2020,' Network Rail said.
It also identified and carried out in-house surveys of 584 sites comparable to Stonehaven.
These specialist inspections 'have not identified any significant issues requiring emergency intervention'. Defects were discovered on around 1% of the sites 'that have deteriorated and require action sooner than originally planned'.
The report outlines how the scale of the issue lies not just in the increased threat from climate change but the enormous amount of legacy assets that need inspection and upgrading.
The inventory of rail earthworks gathered over the last 20 years comprises over 191,000 distinct earthwork assets.
'Most earthworks beside our railway were built more than 150 years ago... they are not as robust as a modern-day equivalent. Such structures are complex to manage due to underlying geology, adjacent environments and assets, and local weather patterns. In the short-term, rebuilding thousands of miles of earthworks to modern day standards is not practicable either from a funding or deliverability perspective.
'Unfortunately, it is simply not economically viable to strengthen all sub-standard infrastructure slopes. Putting this into context our current rate of strengthening through renewal and refurbishment is approximately 3.5% of the asset base in CP6 (2019-2024).'
And this is after investment in earthworks and drainage was nearly doubled from since CP4 (2009-2014) to reach £1.274bn for this current period.
This daunting assessment comes against the backdrop of climate change: 'It is clear from the impact of severe weather events experienced in recent years that this is an area that is accelerating faster than our assumptions.'
Network Rail plans to increase investment monitoring and R&D for earthworks and drainage by more than £60m, and already uses advanced 'machine learning' technology to enhance its earthworks risk hazard scoring with telemetry installed at more than 200 locations.
A forthcoming Environmental Sustainability Strategy will outline Network Rail's ambitions for Climate Change Adaptation and a roadmap to 2050, while throughout CP6 it is developing 'stronger cases for investment to proactively enhance our assets and deliver resilience to future climate change'.
Before the Carmont derailment, 'conventional modelling' identified a need to grow investment for earthworks and drainage in CP7 (2024-2029) by around £300-500m beyond CP6 levels. This will now be reviewed and increased.
Two taskforces were established in August 2020.
Led by Lord Robert Mair, one will review the management of earthworks, while the other, led by Dame Julia Slingo, will look into the best use of weather data.
A review of Network Rail's weather forecasting for rainfall and thunderstorms has already been carried out and the operator is 'exploring the benefits of introducing a ‘real-time’ weather alert system that can better equip us with understanding the local risk of rainfall to our infrastructure and operations'.
The weather advisory task force will also investigate hyper-local solutions including the deployment of readily available spatial resolution rainfall data to a granular level of a 500-metre grid size with images of rainfall rates updated every five minutes.
The review will also provide improved guidance using a ‘high-medium-low' risk alert status aligned with weather forecasts and infrastructure risk registers to determine the appropriate response to implement during adverse and extreme weather.
And for the earthworks themselves, Network Rail is developing new monitoring systems, including surface ‘tilt meter’ technology to warn of sudden earthwork movement.
However, the document warns that 'slopes can fail with little indication of distress prior to failure if a sufficiently high volume of water falls locally'.
'Risk is categorised (using algorithms for consistency) as a combination of the condition of earthworks and the consequence of failure. The condition (or hazard category) ranges from A (lowest likelihood of failure or best condition) to E (highest likelihood of failure or worst condition). The distribution of assets enables prioritisation, with most assets in condition A (c98,000), with reducing quantities B (c46,000), C (c38,000), D (c8,000) and E (c1,000).'
On the morning of 12 August, train 1T08 Aberdeen to Glasgow Queen Street derailed just northeast of Carmont, Aberdeenshire, fatally injuring the driver of the train, the train’s conductor, and one passenger.
After departing Stonehaven, the train was continuing on its southbound journey when it was stopped by an emergency radio message from the signaller at Carmont, who had received a report of a landslip obstructing the line.
Following a period of around two and a half hours waiting for an operations manager to arrive and secure the points, the train was returning to Stonehaven to allow onward travel for the passengers on board. It had reached close to the 75mph line speed. At around 09:38, the train rounded a left-hand curve and struck a pile of washed-out stone covering the line. The front part of the train was derailed by the washed-out material. After striking a bridge parapet, the whole train derailed.
That morning there had been thunderstorms with associated heavy rain across north eastern Scotland. Weather records indicate that over 50mm of rain fell in the Carmont area between 05:00 and 09:00. Heavy rainfall from convection storms disrupted railways and other transport modes over a wide area of eastern Scotland.
This followed a month of greater than average daily rainfall. August brought some challenging weather and it is likely to be one of the wettest Augusts ever recorded in Scotland.
The three people who died in the Stonehaven crash were the train’s driver, Brett McCullough, the conductor, Donald Dinnie, and one passenger, Christopher Stuchbury.