As the advent of the digital railway gathers pace, so the procurement of systems associated with it will need to adapt. It might prove difficult for both customers and suppliers to understand the full impact – as someone once remarked, “the wonderful thing about standards is there are so many to choose from!” and signalling could well be like that going forward.

At the heart of every signalling scheme is an interlocking, as this is fundamental to the safe control of points and signals, and the associated avoidance of trains being routed incorrectly. Interlockings using solid state technology have been around since the early 1980s, but now these have to be interfaced with Radio Block Centres (RBC) to permit the safe issuing of movement authorities for ETCS operation as the entire configuration migrates towards the digital world.

Rail Engineer talked with SNC-Lavalin’s Atkins business to get a supplier’s view on how things are likely to progress.

Framework agreement

In an attempt to simplify and accelerate the procurement process, Network Rail entered into a framework arrangement with three signalling suppliers in 2015. These were Invensys (now Siemens), Signalling Solutions Limited (SSL, now Alstom) and Atkins. Whilst Siemens and Alstom were largely self sufficient in the design, manufacture and provision of signalling equipment, Atkins’ expertise was in signalling design, system integration and testing.

Not having its own products could be both an advantage and disadvantage. On the plus side, Atkins was not locked into any particular equipment type, whilst the downside was that equipment would have to be procured from one or other of its two competitors, which inevitably could mean paying more for the same kit.

The agreement was primarily concerned with the larger signalling projects and still allowed smaller companies (SMEs) to bid for minor schemes.

Having a framework in place has achieved its objectives and several major projects have been delivered under its auspices. It runs until May 2020, but other factors will need to be considered for the future beyond that date. Firstly, the complexities of the declared, and as yet incomplete, merger between Siemens and Alstom may mean that these become a single entity in the signalling supply business, despite currently having two distinct types of product. Secondly, with the advent of the digital railway and the associated accelerated rollout of ERTMS/ETCS/TMS, there are other large companies with the same system capability who would wish to be part of any future framework.

Interlockings

The British solid state interlocking was a joint development between BR Research, Westinghouse (which first became Invensys and is now Siemens) and GEC (now Alstom). It took years both to develop and to get product and safety approval – computer technology, when used for safety critical purposes, being regarded with suspicion by the signal engineers of the day. Nonetheless, it was a significant step forward and paved the way for the later Siemens Westlock and Alstom Smartlock derivatives.

However, the world has moved on and the use of commercial PLCs (programmable logic controllers) as the basis of an interlocking has long been predicted. Developing these to SIL4 (safety integrity level 4) requirements has been challenging but a number of such products are now available.

Several have been introduced as depot signalling solutions, with no significant technical problems having been experienced and generally a considerable reduction in costs. One such is the ElectroLogIXS interlocking, developed originally by GE of America – now also part of Alstom, from which Atkins has a sole-use licence agreement for the UK that extends to 2027. Keen to follow up recent successful commissionings, Atkins is eager to deploy this new-found asset to its maximum advantage.

Old Oak Common depot

London’s Elizabeth Line (Crossrail) is due to open its central core, from Paddington eastwards, in December 2018, with the full cross-London service being introduced in December 2019. Its fleet of trains (the Class 345 Aventra from Bombardier) will be a total of 70 nine-car units, each 205 metres long and with a capacity of 1,500 passengers.

Maintenance and servicing of these trains will be carried out at Old Oak Common, where a huge depot has been constructed which requires a comprehensive signalling system to control all the train movements. The main contractor for construction of the depot has been Taylor Woodrow, with Atkins being given the contract to provide the signalling – the first application of the ElectroLogIXS interlocking under Atkins direction.

The site is vast, having two stabling fans, carriage washer lines and tracks within the maintenance shed. From a signalling viewpoint, there is a higher route complexity than in the Paddington throat. All movements within the depot will be signalled under the supervision of the depot operations controller using a modular control system (MCS) supplied by Alstom and integrated by Atkins. There is also a technician’s terminal that can apply restrictions to the signals, as well as having diagnostic aids. An emergency workstation has been provided in case of the control room being unavailable for any reason, such as an emergency evacuation.

Some statistics give an indication of the complexity of the site:

  • 42 sidings
  • 184 signalled routes
  • 49 point ends
  • 60 signals, both standard lineside and ground types.

Three interlockings are needed for all the possible movements. Eight ‘lock out’ devices are included, which, when operated, prevent signalled movements from taking place in a particular area. These will be used when staff are working in, under or adjacent to a train to avoid any accidents taking place.

Whilst the depot is owned by Rail for London, part of TfL, it has to interface with Network Rail for trains entering or exiting the complex. This section of line is controlled from the Paddington area of Thames Valley ROC at Didcot. The ElectroLogIXS interlocking has been approved for the interface, which will all help towards obtaining generic Network Rail product approval in due course.  During the morning ‘start up’ and the evening ‘put away’, the signalling, which was commissioned on the 23 July 2018, will allow for 12 trains in or out per hour.

Other ElectroLogIXS projects

A PLC can, of course, be programed to fulfil many applications, and the ElectroLogIXS product is being adapted by Atkins for uses other than as an interlocking.

Its first alternative use will be as the level crossing controller at Chilworth on the North Downs line near Guildford. This will be conversion to an MCB CCTV level crossing using Newgate barrier machines, which use an AC motor-driven system rather than hydraulics for barrier arm operation. Statistics indicate that reliability will be significantly improved – the control equipment needed locally is much reduced and can be contained within three lineside cases rather than an REB. The new crossing will be commissioned this autumn.

Feltham Powerbox was brought into service in 1975, so it is over 40 years old, and plans for its replacement are well advanced. As a first stage, the Shepperton branch signalling will be renewed in Spring 2019 with control transferring to Basingstoke Rail Operating Centre (ROC). Atkins was awarded the contract for this project, again using the ElectroLogIXS interlocking for the branch points and signals but having also to develop an interface to the existing Feltham relay-based interlocking.

After several false starts, the re-signalling of the Norwich – Yarmouth – Lowestoft routes is finally happening. Atkins is the chosen contractor, using the ElectroLogIXS interlocking with interfaces to existing signalling at Norwich and to the East Suffolk line at Oulton Broad. The project is due for commissioning in March 2019 and will be controlled from Romford ROC.

The much talked about phase two of East West Rail is at last making progress, beyond the completed Bicester to Oxford stage, and a contract has been awarded to Atkins for signalling the Bicester to Bletchley section using ElectroLogIXS units to provide both interlocking and level crossing controls, all of which will be controlled from Thames Valley ROC.

Finally, the complete renewal of the Feltham signalling area is to be progressed with ElectroLogIXS being declared the interlocking of choice. If the scheme goes to plan, completion will be achieved by 2024, when the whole area will be under the control of Basingstoke ROC.

Product approval and ERTMS implications

As has been hinted, obtaining product approval for safety-critical signalling equipment can be a lengthy process. Given the variation in the application requirements, each of the above projects will be individually assured for both the interlocking functionality and the system interfaces to adjacent signalling and trackside systems. Evidence and performance history will be collated to support a generic application safety case, making the ongoing approval for projects much simpler. The ElectroLogIXS product and associated deployment processes comply with the EN 50126/8/9 standards.

Recent declarations by both the DfT and the digital railway team state that all future re-signalling schemes must be made ERTMS/ETCS ready. Understanding what this means is not necessarily easy and it is much more than just ensuring the interlocking can interface to an RBC. Fundamentals such as signal spacing and block sections have to be aligned to future movement authority limits, which will be designed to increase the capacity of the railway using an ETCS overlay/underlay or a direct transition to in-cab signalling.

Atkins is well aware of these implications and is well placed to understand the principles that will apply to a railway that has to provide for both traditional and digital signalling. Whilst the company does now have an interlocking, it will need to develop its RBC capability with the wider signalling supply chain. This is not as critical as was the case of the three-way framework agreement in that there are many suppliers who have developed RBC hardware – Thales, Ansaldo, Kapsch, Indra as well as Siemens, Alstom and others.

One must not forget GSM-R as part of the ERTMS provision. Upgrading the present voice coverage to give guaranteed data exchanges will require radio expertise and this could well be part of future re-signalling packages. Atkins has recently strengthened this capability following its acquisition by SNC-Lavalin.

So, a new world of railway signalling is slowly emerging, and companies will have to adjust to the new requirements. Those that have the widest portfolio of expertise and products are likely to be dominant players. With its 400-strong team of engineers positioned in premises around the world, Atkins is likely to be one of these, but perhaps the new era will bring in a spirit of mutual co-operation between suppliers rather than the somewhat aggressive competition that has so bedevilled the signalling profession in recent times.

Thanks to Conor Linnell and Edward Mant of Atkins for the information provided.


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