Ben Altman
Senior Research Analyst, RSSB
Low adhesion—causing train wheels to slide and slip on the rails—is a serious risk on the network that can end in fatal incidents, as at Talerddig in 2024.
The rail industry has a range of approaches to prevent low adhesion incidents. These include deploying sand between the wheel and rail, railhead treatments including water jetting, cutting back vegetation, and driver training.
Yet there are multiple challenges.
Sometimes a single solution is not enough and a combination is needed. Sometimes a successful approach in one location isn't effective in another. Sometimes a preferred method may not be the most suitable.
Choosing the most appropriate solution(s) is key to efficiency: improving performance while gaining maximum value from constrained budgets.
And a fundamental question is emerging: how do we know we are choosing the right approach?
That question sits at the heart of our T1341 research project, developed in part in response to Recommendation 9 from the Rail Accident Investigation Branch investigation into the Salisbury Tunnel Junction collision.
The recommendation highlighted the need for a structured framework to assess technologies that help passenger trains cope with low wheel/rail adhesion during braking. This suggestion seeks to move the industry beyond individual solutions towards a more systematic approach.
Introducing our common decision-making framework
The challenge is that train braking capability under low adhesion is rarely dominated by a single factor. Signal locations, infrastructure design, and operational conditions all interact to influence risk and performance.
Choosing one mitigation because it’s worked elsewhere may not necessarily address a specific problem on a particular route.
With T1341, we’ve created a common framework that considers the railway as a complete system rather than a collection of individual factors.
The framework helps organisations classify braking capability, assess operational risk, and understand where interventions are most likely to deliver value.
The aim here isn’t to promote a single technology. Rather, it’s to determine which solution, or combination of solutions, are most appropriate for a particular operating environment.
This represents an important shift. Rather than focusing on rolling stock and infrastructure mitigations in isolation, the framework encourages a different question: ‘What adhesion capability do we need, and what’s the most effective way to achieve it?’
Joining the dots on adhesion management
Now, choosing the right technical solution is only part of the equation. Investment decisions must also be supported by a robust economic case. This is where another RSSB project, T1340, comes in. T1340 developed the economic evidence and appraisal toolkit needed to evaluate low adhesion mitigations consistently. Its case studies showed that different solutions can deliver value under different circumstances, reinforcing the principle that there is rarely a universal answer.
Together, these projects provide something the industry has historically lacked: a joined-up technical and economic framework for decision making. And to bring it to life, we are developing a technical note that provides high-level guidance on applying these two frameworks together.
In an efficient railway, success won’t come from backing a sole mitigation method. It’ll come from understanding the problem first, then deploying the solution(s) that delivers the greatest operational and economic benefit.