Prioritising signalling safety and efficiency in the rail industry

Guest Writer article from James Simester, Technical Director at Unipart.

The integrity of a railway system hinges on the reliability of its most basic component: the lineside signal. For the majority of the UK network, safety is assured by Colour Light Signals (CLS), a technology that must operate reliably regardless of environmental challenges. This system operates against a backdrop of increasing complexity, aging infrastructure, and persistent, historical safety risks.

As we look towards ensuring the performance and safety of the network for decades to come as it transitions to Great British Railways, the industry must move beyond incremental fixes and address two fundamental challenges: mitigating the critical risk of false signal indications, and radically reducing the cost and danger associated with infrastructure renewal.

Firstly, perhaps the most prominent threat to signalling integrity is the ‘phantom aspect.’ This occurs when intense external light (such as low-angle sunlight, reflections from windscreens, or nearby lighting) shines into an unlit signal, causing the signal aspect to appear lit. If a red (stop) signal looks amber (proceed), the potential consequences could be disastrous.

This safety hazard is not new, but regulatory actions highlighted that the problem was often compounded by imperfect alignment during installation and identified the need for a better solution.

The second major systemic challenge lies in the process of renewing obsolete signal assets. Traditional renewal methods are slow, enormously expensive, and unnecessarily hazardous.

Historically, replacing a typical CLS unit required significant track possession time and often involved an extensive installation which can accrue up to 70 total man hours of work. This would often include working at height – a critical safety exposure for trackside personnel. This cost, complexity, and risk can lead to the deferral of signalling renewal schemes, delaying essential safety upgrades due to budgetary constraints. To achieve continuous operational safety and excellence, the industry must adopt solutions that make signalling renewals more affordable, faster, and inherently safer.

Achieving full product acceptance (PA) for next-generation assets is a testament to what is possible when the industry focuses its efforts. For example, The Unipart Dorman Mk3 CLS unit is the result of years of collaborative engineering effort aimed at proving that enhanced network safety and operational simplification are not mutually exclusive. The design features:

• Targeted safety: A new optical assembly, including a groundbreaking Anti-Phantom top yellow module and light-absorbing materials, was developed to significantly reduce the risk of false signals and enhance driver readability.
• Worker protection & efficiency: By leveraging Plug and Play connections, the renewal time is dramatically reduced from approximately 70 total man hours to just seven hours (when used in conjunction with Unipart Dorman’s assisted lift trunnion).

This focus on minimising trackside activity has never been more vital. The industry is currently facing the twin pressures of replacing aging LED signals and managing constant deferral of signalling renewal schemes due to unaffordability.

We need more solutions that are fully retrofittable into existing housings, eliminating the need for major civil works that often drive up complexity and cost. This will enable an ‘install and forget’ philosophy, backed by LED longevity, which drastically reduces maintenance frequency and spares inventory. This approach provides the financial certainty needed to greenlight essential safety renewals.

Furthermore, the deployment of creative, affordable solutions, such as considering the 24V signal version as a battery-backed option for less complex, mechanically signalled areas, demonstrates the commitment required to ensure that technological advancement always prioritises affordability and viability.

While the industry works towards the full adoption of cab-based signalling in future Control Periods, lineside signals will remain essential for decades to come. Asset owners must prioritise investment in technologies that are not only compliant but that fundamentally de-risk and de-cost the network.

These challenges facing the UK rail sector cannot be solved in isolation, and require continuous collaboration between asset owners, partners, and engineering specialists to innovate and improve our rail infrastructure. The achievement of full product acceptance for the Mk3 CLS is a testament to Unipart’s commitment to delivering performance improvement technologies to support the industry. With our extensive experience in rail, and our expertise in delivering trusted, safety-critical assets that meet the dual requirements of modern rail, we can ensure, alongside our partners, that the rail network remains safe, reliable, and sustainable for the future of UK rail performance.

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