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West Country signalling upgrades

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Several recent articles in the railway press have reported on the closure of three mechanical signalboxes in Cornwall as part of an upgrade scheme. Much has been made of the traditional GW lower quadrant signals being replaced with just a touch of sentimentality associated with that. Yet none of these reports have delved into the technology that has replaced the old signalling, nor indeed to explain the reasons for the present project.

Rail Engineer reported in Issue 179 (November 2019), on the introduction of new signalling in Cornwall to achieve a six minute headway in both the up and down directions. That project introduced additional intermediate block sections between Plymouth and Liskeard, Liskeard and Lostwithiel, and Truro and Roskear (near to Camborne); a new control panel at Lostwithiel; and upgrades of level crossings including foot crossings where safety incidents were causing concern. No signalboxes were closed and the lower quadrant signals remained at the box locations. While successful in achieving the capacity gains, it did little to replace the Victorian technology and it was always seen as a stepping stone to eventually bring Cornish Railways into the 21st century.

Visions to modernise the signalling in Cornwall have been around for decades but budgetary constraints have never allowed this to happen and a piecemeal approach is being adopted to introduce more modern signalling. As always in these circumstances, it can lead to work carried out in previous stages being replaced with different technology in the interests of standardisation and contractual preferences. This has been the situation with the latest project.

New Exeter work station covering Cornwall Area. Credit Richard Evans.

Project scope

The need to replace ageing and often unreliable equipment has been the principal reason behind the plan. Much has been made of the Cornish element but the signalling equipment to the east of Plymouth was also causing concern. This was a similar scenario to the recent North Wales coast resignalling, and the Western Territory signal engineers duly took note on what had been achieved there. As such, a contract was let to Siemens Mobility for the design and deployment of its modular signalling system in the Lostwithiel, Par, and Truro signalbox areas.

All were to be controlled from Exeter Power Box, plus replacement of signalling and train detection equipment between Plymouth Tavistock junction and Totnes where it butts to the western extreme of Exeter box. A new supplementary panel in Plymouth Power Box was required, since adapting the existing mimic panel was not practical. Plymouth is the oldest power box in the country, having been commissioned in 1960.

Although the track layout has remained essentially unaltered, some changes have been made to improve operational performance and flexibility.

Modular signalling

Modular signalling has been around for a few years, being developed to reduce the cost of signalling projects on secondary and rural lines. The portfolio of equipment consists of standardised modules that can be manufactured and assembled on a production line and then programmed for whatever the particular application demands. Subsequent testing and proving can also be largely carried out in the factory before being shipped to site for final tests and commissioning. Judged successful, it has been introduced on several re-signalling projects by various suppliers. Modular systems have become the default standard for routes where ETCS may never be justified.

The Siemens Mobility product centres around the Westrace interlocking which is based on ladder logic and is different to the WestLock product that derives from the traditional Solid State Interlocking (SSI) used in busier areas. From the interlocking, a local fibre ring is installed to connect the Object Controllers (OC) which feed the associated signals (OCS), points (OCP), and axle counters (OCA). All are fitted with surge suppression to protect against power variations and lightning strikes. From these, the local wiring connects to the lineside equipment.

A further OC is available for level crossings which can be adapted to whatever type of crossing is required.

The connectivity uses IP (Internet Protocol) coding. Power requirements consist of a battery backed supply at the interlocking from which a three-core 240V cable feeds all OC cabinets where this is transformed and rectified to produce a 24V DC supply for the signals and axle counters and a 120V DC supply for the points which can be of any type but more usually these days are clamp locks.

To control the interlockings and OCs, a further Siemens product known as Westcad is used as the signaller’s work station located in Exeter PSB. To connect the Westcad to the interlockings, which are often many miles distant, use is made of the Network Rail Telecoms FTNx network that provides a resilient IP coded digital transmission link to ‘points of presence’ along the railway. FTNx is there for the use of all rail disciplines but signal engineers are satisfied that it provides the integrity for the transmission and distribution of signal control information.

Credit: Siemens.

The Cornwall project

As stated, three signalboxes have been abolished where age and reliability of equipment was becoming an increasing concern. Westrace interlocking ‘islands’ have been provided at Truro, St Austell, Par, and Lostwithiel, with ‘slave islands’ at Chacewater (the boundary to Roskear) and Penryn on the Falmouth branch, also at Liskeard where the box is retained for the interface to Plymouth. The signalling at Liskeard is unaltered including the retention of track circuits.

The signalling plan was to produce continuous train detection by means of the axle counters but with discrete block sections of a home and distant signal commensurate with the six minute headway. New signals have been provided throughout the Cornish section, most of these being the Dorman fold down type with a single LED aspect showing either red / green or yellow / green. Connecting the interlockings to the OCs and locally to the trackside items is by the use of armoured cables laid in the cess or in troughing routes where these exist. Recovering old cable is an ongoing challenge.

At Lostwithiel, the existing Intermediate Block (IB) sections at Largin (where the route is reduced to single track over two adjacent viaducts) and at Bodmin Parkway are retained, but have been re-equipped with new signals. The recently installed panel at Lostwithiel and associated SSI equipment has been made redundant but with the intention to re-use these elsewhere. Re-positioning of signals at Lostwithiel station included moving the down home signal westwards in order to prevent stopping trains from fouling the level crossing. The junction for the branch to Carne Point near Fowey is controlled from the interlocking as are the holding sidings for china clay and engineering trains on the Exeter side of the crossing. Control of the level crossing is now by CCTV monitoring using a 6Mbit link from Exeter PSB where, because of the closer signal sections, the down time of the barriers can be reduced.

At Par, the new signals are located at the end of each platform including the loop line platform, which retains its reversible working to allow trains to and from the Newquay branch to leave the station in either a west or east direction. All points in the station area are controlled by clamp locks from the interlocking, but the junction signal and indicator towards Newquay is mounted on a special twin post provided by Collis. The points that allow china clay trains from Goonbarrow on the Newquay line to be held in sidings are also now fitted with clamp locks which makes it easier to route trains direct into these rather than occupying the Newquay platform. At Burngullow, the St Austell Westrace interlocking controls the access to the china clay works sidings and the branch to Parkandillack. The SSI at Par to control the St. Austell and Probus IB sections has been recovered and the signals are renewed with the Dorman type.

Truro has significant passenger train movements because of the busy Falmouth branch with its 30-minute interval service. The track layout and signal positioning have been altered to take account of this. The previous trailing crossover on a curve to the east side of the level crossing has been replaced by a facing crossover on straight track between the two Truro viaducts. This facilitates westbound trains being routed into the up platform should there be a problem on the Falmouth branch requiring trains to depart from the down platform instead of the bay.

Plymouth Hemerden Work Station. Credit: Clive Kessell.

The level crossing immediately east of the main platforms has been converted to automated obstacle detection operation (MCB OD) but still requires east bound trains to have the barriers closed before the protecting signal into the station can be cleared to green. This is because of the falling gradient from the Penzance direction. The IB sections westwards towards Roskear at Chacewater and Redruth are retained but with new signals provided.

At Penryn on the Falmouth branch, the control of the passing loop is now from the new Westrace slave island although the existing signals and point mechanisms have been retained.

The display of train descriptions which ended at Liskeard is now extended to Roskear as the fringe to the Exeter control panel. A new train describer screen has been provided at Liskeard but, from Roskear to Penzance, traditional block bell signals remain for train type identification.

At Exeter, the Siemens Direct Route Setting (DRS) system is provided which uses timetable data from the nightly download to provide a degree of automatic route setting, but leaves the signallers to make final regulatory decisions. A TMS (Traffic Management System) might be installed later that should assist with optimising train routing and regulation.

The Devon element

Replacing the unreliable Aster track circuits and improving the line capacity east of Plymouth towards Totnes became part of the overall project. The track circuits are replaced with Frauscher axle counters. The existing signal spacing was not ideal, there being some very long block sections that adversely impacted on capacity, so the decision was made to provide 10 new signal sections equally spaced. This has necessitated the abolition of the Hemerdon loops but, in practice, keeping freight trains moving is a better policy.

A new Westrace interlocking has been provided at Wrangaton (roughly the halfway point) with slave islands at Tavistock Junction and Totnes. All signals in this section have been replaced with the two aspect Dorman type except at Ivybridge where new three aspect signals are provided to cater for optimum regulation of stopping trains. The power feed has been converted from the 650V lineside supply where voltage drop was a problem, to the new 240V standard as per Cornwall. A new Westcad work station has been installed over the section of redundant panel in Plymouth box to control this section.

Telecommunications and radio

The policy of providing SPTs at signals has been continued except at the very remotest of locations where track to train communication relies solely on the GSM-R radio. Regarding the latter, the routing of radio calls to the various signallers has had to be adjusted to take account of the new block section positions.

Training and competence

For a railway largely equipped with mechanical signalling and only limited electronics, this project has introduced new systems for which training of the maintenance and technical support staff is needed. The S&T depot for Cornwall is at Par where 18 staff give 24/7 cover working in 12-hour shifts for the area from Penzance to Totnes. To facilitate their training and familiarisation, a Westrace interlocking training suite complete with a signalling control panel, object controllers, signals, and axle counters has been set up in the depot. A five-day training course is given by Setec which is repeated periodically. During the training, faults can be put on for technicians to diagnose and then rectify. The fault log screens at the various interlockings can be replicated in the training room to give staff an understanding on what can happen and what to look for.

At present, the training on clamp locks is carried out at Bristol and that for Westcad work stations is done at Exeter. It is the intention to have a Westcad system provided at Par. For the Devon section, similar training is carried out at Exeter.

The project intention has been to standardise equipment types, hence the removal of SSI units, Thales axle counters, and different types of signal heads and point machines. Having things all the same is a worthwhile objective and helps the maintainer to manage the number of competence certificates that are held and retained.

Par Local Fibre Ring Terminal Boxes. Credit: Clive Kessell.

Project finances and contractual control

The project was authorised at £75 million but has ended up costing a fraction over £100 million. Many reasons exist for the increased spend, inflation being the main cause, but there were also delays in getting material and access. The war in Ukraine was a factor as the steel tape armouring for the fibre cables became difficult to obtain.

As to timescale, these factors have introduced delay; the Cornwall area was due for commissioning in November 2023 but was put back to February/March 2024 and the Devon section which was due in February was delayed to just before Easter 2024. Compared to other projects, this represents only minor slippage.

Most of the problems have been with the civil engineering elements where a shortage of labour available to work, stay, and/or commute was a challenge. Eventually, Siemens was able to increase the workforce by transferring contractors from South Wales after finishing Port Talbot West re-signalling and Transport for Wales (TfW) projects in the Cardiff Valleys. The ceasing of red zone working or restrictions on walking has been a factor with most deliveries, with work being achieved during short possession periods in Cornwall. However, in conjunction with GWR and CrossCountry, Network Rail was able to agree extended midweek access through the Hermerden area to achieve improved overnight working arrangements over a period of 18 weeks during the autumn and winter. This helped to control the increasing project cost.

The contract methodology was the hub and spoke arrangement with Network Rail being in overall control, Siemens Mobility being the equipment supplier plus subcontractors working for them and Construction Services doing the track alteration work.

Additional work was undertaken by Colas Rail outside of the main re-signalling footprint to carry out renewal and upgrades to two level crossings on each of the Looe and Gunnislake branches, plus other minor renewals of signal structures in Cornwall. Three of the level crossings upgrades were completed in March concurrent with the re-signalling programme.

Post commissioning and the future

The commissioning required blockades and bus substitution but since being brought into service, the system has worked well, and the benefits are being realised. Some niggling faults have emerged but that is typical while equipment beds in. Overall, the system is yielding significant performance benefits and should be a potential catalyst for ongoing transport improvements across Cornwall in the coming years.

For the future, mechanical boxes remain at Liskeard, Roskear, St Erth, and Penzance along with the ageing power box at Plymouth. Eventually, these will have to be replaced. Network Rail has commenced the development of a Plymouth re-signalling project and will assess the other mechanical boxes for a future control period. These may be around for a good few years yet.

Thanks are expressed to Richard Evans, programme manager for Network Rail and Simon Rhodes, the Network Rail techNical expert, for the opportunity to visit the sites and have the project explained in detail.

Lead image credit: Clive Kessell


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