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Call 01530 816 444 or visit www.railstaff.co.uk for more information trigger actions from the deployment of a watch person to a reduction in speed to reduce the dynamic forces on the track during periods of hot weather.

This is a complex task, and the CRT Register has many thousands of entries, but the net result is that additional precautions must be put in place in hot weather if a deficiency or low SFT leads to a low CRT. The stress-free temperature of CWR is recorded in a national database, Rail Stress. This database is used to record the original installation SFT and any activities that may have reduced the original SFT. Any deficiencies and reductions to the SFT are recorded in the CRT Register.

Brian reported that despite 2022’s hot weather, there were only 26 recorded buckles, compared with a peak of 131 in 2003. However, despite the small number of buckles which was positive for safety, performance was poor due to speed restrictions and some line closures on the hottest days. He added that the latter were not all track issues. For example, there were concerns about sagging overhead line and passengers trapped in sealed coaches with no electricity supply. Of the 26 buckles, it was found that only five were on the CRT register and only one was subject to a speed restriction. Follow up analysis suggests 25 out of 26 should have been on the CRT register. The root cause of most of the buckles was failure to identify the local areas of deficient track rather than inadequate preparation work.

He wondered whether the majority of buckles were simply a small number of sites that had slipped through the deficiency identification process, compared to the many hundreds that were correctly recorded, managed, and prepared/mitigated through the application of speed restrictions?

Brian concluded that:

» Only 20% of the buckle sites were correctly recorded in the CRT Register

» With hindsight, all but one of the sites should have been on the Register

» Extensive blanket speeds and route closures were applied at the expense of performance and passenger needs

» Changes to track construction specifications have generally led to a greater strength and capacity to manage extreme temperatures.

» Effectiveness and practical use of watch persons with available resources and access in a modern railway needs to be reconsidered

» Technology, RCM, and effective preparation, needs to focus on higher risk sites.

Vtism

Andy Rhodes, business development manager and principal consultant at Serco Rail Technical Services, gave an update on upgrading the Vehicle Track Interaction Strategic Model (VTISM), RSSB Project T1258. VTISM was originally released in 2006 and integrates various engineering models to help managers make strategic decisions such as cost forecasts, as shown in the diagram below and the table on page 37.

This upgrade will support Microsoft 365 and Windows 10 environments as well as including current track asset policies adopted by Network Rail and ensuring accurate predictions of: track damage and costs; recent asset renewals; unit costs; traffic changes; improved knowledge on asset behaviour; changes in renewal; maintenance and inspection policies, e.g., refurbishment activities; and review underlying model assumptions (track geometry and ride forces). It will also include a number of technical refinements including: increasing the range of applications by extending VTISM’s library of routes and vehicle models; including further cost modelling capability (manual maintenance, safety, delays); and evaluating latest track damage research.

Adhere

The Adhesion Research Group is facilitated by RSSB and has over 50 members from various backgrounds. It acts as sponsor for the ADHEsion REsearch challenge (ADHERE) programme, proposing and supporting delivery of research projects, whilst seeking ways of implementing solid research findings. It cooperates with the Seasonal Challenge Steering Group (SCSG) and Seasonal Challenge Communications Group (SCCG), to ensure that opportunities to implement successful research are seized. Jordan Brant from the University of Huddersfield presented “Developing Highly Adherent Leaf Layers” seeking to understand how/why leaves bond to the rails in the way that causes so many problems. Experiments were carried out on the University’s HAROLD test rig which uses full size rail wheels on large diameter rollers representing rails. Jordan explained that the tests were carried out using a process that allows several factors (load, water, leaf type, rust) without having to vary each factor independently. This work delivered some useful results including:

» American oak leaves had a higher bonding strength than sycamore leaves for a given test input

» Iron oxide increased bonding strength

» The HAROLD leaf layer is chemically different to layers generated using small scale tests

» Higher wheel loads remove more of the leaf layer during braking tests

» A small number of leaves can produce a consistent black leaf layer and very low adhesion

» Sycamore leaves were more durable than the American oak leaves

» A standardised method for measuring leaf layer bonding strength has been developed, untreated leaf layer and the type of enzymes that have better performance.

» Consistent leaf layer production is useful for standardising low adhesion rail cleaning tests.

Professor Lewis also introduced Morinoye O. Foloronso who presented University of Sheffield’s work on ‘Low Adhesion Estimation through Video Image Machine Learning’ (RSSB project COF-UOS22-02) and from her PhD, ‘Improving Prediction of Low Adhesion Friction considering Transience’ (RSSB project COF-UOS-05).

Previous work had demonstrated that forward facing and downward facing video could be used to detect likely poor adhesion but on its own was not enough. The video might identify the black layer on the rails, moisture, oxides and/or other contamination of the rail, but there was no good mathematical description of the data from these images. In addition, information about temperature and humidity is required. Hence, a machine learning technique was proposed as shown in the diagram below.

It was noted that the aerodynamics of leaves is an important factor in determining which leaves are more likely to be drawn into the wheel rail interface.

Dr Leonardo Gomez, University of York and Professor Roger Lewis, University of Sheffield, discussed ‘Understanding the Polysaccharide Composition of Crushed Leaves and Evaluating Potential Enzyme Treatments’ (RSSB project COF-G24-01). They established the range of leaf constituents, including cell wall polysaccharides, tannins, and lignin, that could cause low adhesion effects, and proposed adhesion mitigation through the use of enzymes that will digest the responsible molecular structures.

These hypotheses were subjected to a series of tests, though more work under conditions closer to the rail environment is required to complete the activity. The present work has established that leaf layer enzyme treatment increased traction over that seen with an

To make the model work, real data was required and over 600 data points (an image of the rail head, an image of the surroundings, temperature, humidity, and a friction measurement) were collected from six separate sites during autumn and winter of 2019 and 2020. It was also necessary to use traditional image analysis techniques illustrated in the diagram. The aim was to have a few numbers (e.g., colour, edge, brightness) rather than thousands of pixels.

Morinoye showed a device fitted with forward facing and downward cameras, analogue and infrared thermometers, and GPS sensors that can be fitted to a train’s lamp bracket together with microcontrollers for recording and translating sensor data. This is being trialled on the Wensleydale Railway.

Validation has shown positive results, but Morinoye explained that it has yet to be confirmed that the prediction tool has a robust data bank. The potential uses for the tool include: informing drivers of following trains of problems in real time; identifying where treatment is needed (e.g., in combination with cleaning technology); building up data on low adhesion conditions for mitigation planning; verifying low adhesion forecasts; and helping to understand the process by which contamination builds up.

Loughborough and Sheffield Universities, and Perpetuum (now part of Hitachi), he also paid tribute to the late Professor Roger Goodall whose idea this was back 20 years ago. This project involved carrying out tests using a Network Rail Multi Purpose Vehicle (MPV).

The basis of the work was that different movements infer different adhesion levels. In the longitudinal direction, this is familiar with wheel spin or slip highlighting low adhesion. But this is only apparent when accelerating or decelerating. Could changes in lateral and yaw dynamics provide continuous adhesion measurement?

Test were carried out in summer 2022. Chris observed that delivering low adhesion during a heat wave was “a challenge”. Before carrying out the track tests, the MPV was simulated in Simpack with correct dimensions, weights, suspension, and drive parameters. In addition, the proposed instrumentation was modelled. Sensors were fitted to axleboxes, bogies and body, GPS was fitted, and brake pressure and wheel speed were measured.

Chris said that the data is still being analysed, in particular to filter a lot of noise on the signals. He concluded that the algorithms developed so far are promising and validate the concept of vehicle dynamics variation with adhesion change. The next steps will be to bring the various methods together and identify a commercial proposition.

Tests were carried out at RIDC Tuxford on a flat and straight section with sufficient acceleration and braking zones. The test area was approximately 400 metres long (the practical limit for producing areas of low adhesion but allowing for the collection of sufficient data for each run). The lowest adhesion level was provided by wetted paper tape – a big challenge during the hot weather. Tests were carried out in both wet and dry conditions delivering high, intermediate, and low friction at mostly constant speeds of 10, 40, and 60 mph. Tribometer friction measurements were taken before and after each run. Coefficients of friction between 0.1 and 0.3 were achieved. Over 12 running days, tests were actually carried out at 16, 26, 40, and 60mph. The lower speeds varied from the plan because of gear change speeds on the MPV. A total of 83 runs took place and up to 30GB of data per day was generated.

Conclusion

ADHERE and, to an extent, V/TSIC 2023, focussed on research projects that are some way from commercial exploitation. It will be interesting to follow their progress.

With thanks to the presenters and to Ben Altman from RSSB for their assistance in preparing this article.