Better possession protection

In 1841 Edward Alfred Cowper, a founder member of the IMechE, devised a warning signal for trains on foggy days. This had a detonating compound packed into a small circular container and was fastened to the rails by lead clips. By 1844 such fog signals were in widespread use and their use was enshrined into the Rule Books of the day. Over 180 years later, this is still the case.

Although the widespread introduction of the Automatic Warning Systems in the 1950s and 1960s removed the need for fog signals, millions of detonators are still in use. At the very least, six detonators are required to protect the 100,000 engineering possessions taken each year and each driving cab must carry 10 detonators to protect the line in the event of a train accident.

Detonators have been used to protect engineering work for over 100 years as specified in the 1950 British Rail Rule Book which required three detonators to be placed 10 yards apart for this purpose. The theory is that detonators will stop irregular moves of engineering trains out of possessions, and of service trains into possessions, as well as providing a warning to track workers of such unauthorised train moves.

RAIB reports

In 2015 the Rail Accident Investigation Branch (RAIB) undertook a class investigation into protection arrangements during engineering work. This found that in a two-year period up to April 2013 the number of protection irregularities were:

• 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.

At Camden South Junction in 2017, a train was signalled over a line on which a possession support worker (PSW) was placing possession as authorised by the person in charge of possession (PICOP). The PICOP had taken a possession at 2300 and, immediately prior to the incident had extended the possession at 0100 to include additional lines. Whilst doing so, the PICOP had spent one minute 19 seconds reading the list of the possession limits from the weekly operating notice (WON) to the signaller. When the signaller then placed reminder appliances for the possession, he omitted to place one on signal WM494 which protected Line A where the PSW was placing protection. This was the last of a nine-line item in the WON for the possession extension.

The RAIB report into this incident considers why the signaller omitted to place a reminder appliance and concludes that this was associated with processes and methods for managing and communicating information regarding engineering work in modern, multi-panel signalling centres.

The report considered that another underlying factor was that the possession set up process requires people to be present on track and so exposes them to risk in the transition period before protection is fully implemented.

In this respect the report recommended that it required Network Rail review its possession management process to reduce the need for staff to be on the track for possession protection and that this review should consider newly developed technologies.

RSSB reports

This recommendation would have been well received by those who, for many years, have considered that there must be safer way of protecting possessions than placing detonators. Yet this was not the conclusion of the RSSB reports that have investigated this issue. In 2005, a review on the continued use of detonators (report T507) concluded that detonators should not be replaced in T3 possessions but did show how three countries (Spain, Austria, and Italy) were able to protect engineering work without the use of detonators.

In 2019, the effectiveness of detonator and possession limit board protection (report T1167) was assessed by practical tests on the audibility of detonators. These concluded that they are not a reliable method of altering drivers of a possession and of alerting track workers of the presence of an approaching train. Yet, in 2020, a quantified risk assessment on the use of detonators and alternatives (report T1115) proposed that no changes should be made to T3 possession rules.

Nevertheless, these reports did show how other countries protect their railway engineering work without the use of detonators and that the effectiveness of detonators is questionable. Indeed, on the basis of the T1167 report, the risk assessment in report T1115 considered that detonators are only 50% effective.

Detonator free possessions

A recommendation from RAIB’s Camden Junction report is for a review of the need for staff to be on track for the purpose of taking and giving back a possession.

Network Rail’s Track Worker Safe Access Strategy is addressing this recommendation with a possession  limit controls initiative which is considering how current and emerging technology could provide safer protection. This is assessing different possession protection methods such as signal disconnections (T3-D) and activation of equipment such as remote-control track circuit operating devices (T3-A). A derogation to the Rule Book was obtained to protect possession in this way in February 2024. Since then, the T3-D and T3-A protection has been successfully trialled in Tyneside and Selby.

A radical application of T3-A protection is being trialled in Scotland. This links the possession planning process directly to the signalling system to enable verified possessions to be pre-programmed into the system. This eliminates both the risk of a misunderstanding between PICOP and signaller at the time of the possession and of the signaller mistakenly signalling trains into the possession as happened in the Camden incident.

To learn more, Rail Engineer was glad of the opportunity to visit Edinburgh Signalling Centre to discuss this initiative with Craig Milne, Network Rail Scotland’s planning and logistics director.

Initiate, Luminate, and Scalable

The Edinburgh Signalling Centre is an integrated electronic control centre (IECC). These were developed in the late 1980s by British Rail Research and have VDU displays which replaced the switch and button panel control in earlier signalling centres. They also have an automatic route setting (ARS) system which makes automatic signalling control decisions based on the train timetable.

After rail privatisation, British Rail Research was acquired by AEA Technology, the rail business of which was acquired by DeltaRail in 2006. In 2012, DeltaRail launched IECC Scalable so that IECCs can use modern hardware platforms and software architecture. DeltaRail became Resonate in 2016, which thus has the pedigree to support and maintain IECC systems. 

Resonate’s traffic management system, Luminate, was introduced on Network Rail’s Western and Anglia routes in 2018 and 2021. It was introduced at the Edinburgh Signalling Centre early last year. Luminate can identify traffic conflicts, validate contingency plans and has a platform docker tool. Since its introduction in Scotland, the public performance measure (PPM) for trains managed through Luminate is 7% higher than those that were not. Luminate’s provision of the best platform docking options has also significantly reduced delays at Edinburgh Waverley and Glasgow Queen Street stations.

A recent development is Resonate’s Initiate infrastructure access planning system which links engineering access planning to the signalling system. Planners create possessions (or line blockages) in Initiate which must then be validated by an approver. Once the possession has been approved, its limits are fed to the Scalable system which controls the signalling interlocking. When the possession is taken, this locks signals to ensure trains cannot be signalled into the possession. Thus, it is a form of T3-D protection as the signaller has no control of the protecting signals during the possession. 

Craig explains that much has been done during the past 12 months to enable Initiative to provide possession protection in this way. This includes the Systems Review Panel’s approval of the Initiate system, developing instructions for its use and the industry access board’s approval of a trial for its use as part of the possession limit controls programme. The personnel concerned and Trade Unions also had to be consulted.

As part of these approvals, a hazard study was undertaken which concluded that, in the protection hierarchy, Initiate was the highest form of protection. This validated the proposition that detonator protection was not required when possessions are taken by the Initiate system.

Training also had to be provided to planners, signallers, Persons in Charge (PIC), and others who use the Initiate system. As Initiate can be used to take both possessions and line blockages the individual who requests Initiate protection is known as the PIC. For wider use of the system, there is to be a full programme of internal and industry communications.

Initiate’s first possession

In a UK first, Edinburgh Signalling Centre authorised its first Initiate possession without detonators on 13 January. Craig explains that the process for this is:

• Possessions are created, verified, and approved in Initiate in accordance with normal possession planning timescales.
• Once approved, possession details are sent to Scalable and Luminate 72 hours before the possession start time.
• Approved possession details are shown in Luminate 36 hours before possession start time.
• Signallers can see the possessions displayed in Scalable six hours before the possession start time.
• PICs can view the Initiate plan once they have been allocated to the possession/line blockage.

Normal PIC / signaller communications apply when requesting a protection with the additional requirement of the PIC advising the Signaller of a unique code.

Once signalling protection has been applied the signaller cannot change anything with the limits of the possession / line blockage until it is given up by the PIC advising the signaller of a unique removal code.

If there is a requirement to operate signalling equipment during the possession e.g. move points or for signal testing, the individual requiring this must get authority from the PIC who will issue the signaller with a temporary override code which is valid for two-minutes.

The first Initiate possessions were taken on the Cumbernauld workstation. Thereafter, as shown on the diagram, the system will be progressively rolled out until all nine Edinburgh Signalling Centre workstations will be taking Initiate possessions from July.

Craig is clearly enthusiastic about the introduction of Initiate and has every right to be so. Although almost all of the 14,000 possessions each year in Scotland are taken without incident, in Control Period 6 there were an average 16 incidents per year involving protection or trains signalled towards a line blockade. This is an incident rate of 1 in 1,000 possessions.

Speed and safety

Furthermore, the use of Initiate reduces the number of safety critical communications required to take and give up possessions from an average of 18 calls to three taking account of the need for the PICOP to communicate with those who place protection. This offers a significant safety benefit as safety critical communication failures are a significant incident causation factor. Another safety benefit is that there is no requirement for staff to be on track to place and remove protection before and after the possession is taken.

In its report into the fatal accident at Margam in 2019 that killed two track workers, an RAIB recommendation concerned the need to provide safe access to the track for routine maintenance. Although line blockages provide such safe access, their use is often not practicable due to the time to set them up between trains. Craig considers that Initiate has much to offer in this respect as he estimates that the slick, safe way that it offers protection will enable an additional 3,000 line blockages a year to be taken in the Edinburgh Signalling Centre area.

In addition to its safety benefits, the speed at which Initiate possessions can be taken and given up increases available track access time. Experience to date has shown that Initiate track access is granted in two to three minutes compared to the 20 minutes it normally takes with similar time savings at the end of the possession. With a normal overnight rules of route possession of typically six hours, this offers a 10% increase in productive access time.

A 2021 ORR report on possession efficiency noted that, typically, Network Rail’s supply chain undertakes 700,000 hours work within possessions with 100,000 possessions each year. This indicates the scale of the total efficiency savings from the network wide application of Initiate or a similar process. It should be noted that Initiate is only available alongside the Scalable system.

The use of Initiate to take possessions and line blockages improves a process that has long been prone to human error, however competent the individuals concerned may be. One issue identified in the RAIB report into the Camden Junction incident was “the processes and methods for managing and communicating information regarding engineering work in modern signalling centres”. The need for a PICOP to spend over a minute reading the details of a complex possession in the WON to a signaller is one such example.

The Initiate initiative effectively addresses this issue as well as the need to put people on track before the possession is taken. It has done so by considering the whole possession process, the provision of comprehensible information to those involved, and applying modern technology to deliver significant safety and efficiency benefits.

It is an impressive example of the dictum that good safety is good business.

Image credit: Network Rail