A way to measure low adhesion for testing in the field
Low adhesion caused by moisture mixing with the film produced by 'leaves on the line’ disrupts passenger journeys and causes safety risks, such as signals passed at danger and station overruns.
Rail cleaning methods, friction enhancing products and traction gels, are used to tackle low adhesion. Testing is needed to determine how effective these mitigations are and to optimise how they are used.
Some tests can be done in the lab, but field tests are also needed. They provide an important way to test mitigations under the conditions found on the operational railway. No standardised approach to carry out such tests exists. This has a negative impact on the robustness and validity of test results.
Information about existing guidance and field test practises was collated and reviewed. Good practice was established and explained.
The report includes guidance on:
- site selection and management
- forming simulated leaf layers that can be consistently reproduced
- capturing environmental data
- tools and techniques for measuring leaf layer thickness and bond strength, and railhead friction.
The work was undertaken through the RSSB-University of Sheffield research partnership on the wheel-rail interface.
Standardising the approach to simulating leaf layers can save time, reduce costs, and provide assurance about the validity of findings.
It might also yield insights from comparisons between different tests and trials. This would make it easier to compare the performance of low adhesion mitigations.
The guidance and measurement protocols can be used to:
- optimise rail cleaning methods and the application of friction management products
- assess the effectiveness of new solutions.