Background
Historically, intrusive railway engineering works have been carried out within a traditional T3 possession, using possession limit boards (PLB) and detonators for protection.
This method requires track workers to place PLB’s and detonators at the extremities of the possession limits. This imposes a risk to track workers, exposing them to unnecessary hazards, such as encroaching on or towards open lines when deploying and retrieving their protection equipment. There is also anecdotal evidence that too regularly, protection equipment is being placed on the wrong line or even outside the possession limits.
Over the years, due to better insights and reporting, concerns have grown about the safety of using PLBs and detonators and in 2015, the Rail Accident Investigation Branch (RAIB) conducted a review into the protection measures used during engineering possession works. Over a period of two years, they found a number of protection irregularities:
- 144 – protection incorrectly placed
- 39 – protection set up whilst the line is open to traffic
- 52 – working outside protected area
- 52 – trains signalling into the protected area
These figures highlighted the challenges faced by teams out on track and were a cause for major concern, ultimately paving the way for two deviations to the current Rule Book, called T3-A and T3-D. These are updates to the existing processes for the protection of T3 possessions on Network Rail managed infrastructure, that use existing technology to reduce that safety risk.
T3-A possessions use technologies which are controlled remotely by a mobile app or SMS, such as a remote T-COD (ZKL 3000 RC) or a remote disconnection device (RSS – remote safety switch). This has improved how possessions are taken, protected and handed back significantly, reducing on-track exposure to allow for a safer, smarter and more efficient way of working.
T3-A trials involving the use of a remote-control T-COD, specifically the ZKL 3000 RC, were successfully conducted at Selby Junction on the North & East Route in 2024.
The successful completion of these trials was evidenced through:
- The output report
- The after action-action review
- A series of video recordings of the possession activities
- A wash-up meeting to capture feedback and identify areas requiring further development
The positive outcome from these trials provided the TransPennine Route Upgrade (TRU) project with the opportunity to adopt the T3-A model, successfully deploying the devices on the lines between York and Leeds. Within a matter of weeks, the project team could see the real benefits in terms of cost and time efficiencies.
You can read more about the trial and the efficiencies gained during the TRU project here.
Problem
The article Improving Track Worker Safety, published on 28 October 2025, highlights that around 8% of possessions are currently delivered using T3-A or T3-D protection, enabling 6% more work to be completed while carrying only two thirds of the risk. It also sets out Network Rail’s ambition for regions to achieve 80% adoption of T3-A and T3-D protection by 2029.
Despite this clear strategic direction, the use of T3-A remains uneven across the network. While some areas are adopting the approach at pace and realising its benefits, traditional T3 methods continue to be widely used where T3-A is available. This inconsistency limits the realisation of the safety, efficiency and productivity gains that T3-A is designed to deliver.
A traditional T3 (now T3-H) possession in comparison to T3-A continues to increase costs, risk to track workers, time deploying/recovering and carbon emissions – due to the following:
- Additional cost of possession support staff (PSS) to place and recover protection
- Cost of equipment i.e. PLBs and detonators
- Cost and time to produce multiple Safe System of Work Packs (SSWP) that require verifying and validating
- Increased risk as multiple PSS working on or near the line
- Increased risk of deploying protection incorrectly
- Risk of misinterpretation due to high volume of safety critical communications between signallers, PICOPs and PSS
- Production time reduced through placing and recovering protection
- Increased carbon emissions due to multiple vehicles travelling to and from possession limits
In addition, recent findings show that modern train cabs provide a much better environment for the drivers, including significantly improved soundproofing compared with older models. However, this reduces the effectiveness of detonators as an audible warning method. This issue is particularly evident on Pendolino trains, where the driver’s cab is positioned further back. As a result, drivers may not hear or feel the effect of the detonators placed on the track and may therefore be unaware they are approaching a worksite until it is too late.
Solution
Network Rail’s introduction of T3-A possessions using the ZKL 3000 RC (remote-control track circuit operating device) clearly demonstrates its recognition of the benefits of applying technology where appropriate.
Recent data supports the view that T3-A provides a more efficient, safer, faster and more reliable method of protection.
Benefits include:
- The PICOP is no longer reliant on PSS placing and recovering protection
- Protection can be deployed instantly through the MTinfo 3000 app, activating an unlimited number of ZKL 3000 RCs within seconds
- Reduces safety critical communications
- Less cancelled possessions due to not relying on PSS, protection can still be deployed if PSS fail to attend shifts
- Planning access for PSS no longer required
- Reduced or restricted amounts of access points are no longer an issue
- Reduces impact of walking on ballast or encroaching on third rail etc.
Efficiencies
Transitioning from T3 to T3-A possessions across several Kent routes has delivered measurable efficiency improvements over a fixed period.
Over a period of five shifts this has equated to:
| Route | Time Saving Per Possession | Time Savings Over 5 Shifts |
|---|---|---|
| Maidstone Lines (SBJ) Otford-Lenham | 40 mins | 3 hours 20 mins |
| Mid Kent Lines (LCH) -Ladywell Jn-Hayes | 15 mins | 1 hour 15 mins |
| Maidstone Lines (SBJ) Maidstone East-Ashford | 15 mins | 1 hour 15 mins |
| Maidstone Lines (SBJ) Maidstone East-Hothfield | 19 mins | 1 hour 35 mins |
The cost efficiencies speak for themselves – imagine the annual savings achievable through area-wide deployment of T3-A possessions.
Driving Change
Across several routes, T3-A protection is being successfully adopted for possessions, with clear benefits already being realised. This growing experience provides a strong foundation for wider transition from traditional T3 methods where T3-A is available.
As planners consider future possession strategies, the evidence demonstrating the safety, efficiency and reliability of T3-A should play a central role in decision-making. Continued exposure to successful applications is key to building familiarity and confidence.
By expanding shared learning around T3-A – showcasing practical use cases, success stories and proven best practice – we can accelerate adoption and support a consistent, business-as-usual approach to possession delivery.
Conclusion
T3-A was identified as a necessary evolution of traditional protection methods following a history of safety incidents. What began as a concept has progressed through multiple successful trials and is now recognised as the preferred method of protection across many routes.
By continuing to highlight these improvements – alongside the clear safety benefits and efficiency gains achieved – confidence can be built across the industry. This provides track workers with reassurance that T3-A represents the most effective form of protection, supporting the shared objective of everyone returning home safe every day.
Michael Doherty, Network Rail, Kent Route, said:We successfully installed ZKL devices while still maintaining services from the bay platform at Maidstone East. The solution has proven effective, and we’ve now implemented our third T3-A possession — saving approximately 17 minutes during both the granting and giving-up process. A great step forward in efficiency and service continuity!
For more information about the T3-A using the ZKL 3000 RC, get in touch at [email protected]
