Much has already been written on the impending track work at Reading Station, eliminating flat junctions and permitting more flexible operation. All this will mean significant changes to the signalling system which has to be progressed as a series of stageworks to commission the new layout. The first extension involves additional through platforms to the north requiring the demolition of the existing power signal box (PSB) and telephone exchange. Network Rail decided to provide a control centre for the entire area with a new interlocking, making it much easier to accommodate the ongoing moves and changes. This phase of the project, known as Reading Station Signalling Enabling Works, was accomplished in December 2010.
Reading’s recent past
Reading entered the power box era in 1965 with a free-wired interlocking built to the then-BR Western Region (WR) standard E10000 series of drawings. This controlled the Reading area and Didcot, with fringe boxes at Twyford and Southcote Junction amongst others. Remote relay rooms existed at Sonning, Spur Junction (where the ex-Southern lines link in), as well as Reading West and Oxford Road at each end of the triangle west of the station. The control panel provided by Henry Williams had a near-horizontal desk using the turn-push system for route setting and a supplementary upright display incorporating the train describer windows and buttons for the Signal Post Telephones (SPT). This system was designed to accommodate up to 25 phones on a single line but with identity and secrecy of conversation built in.
The E10000 standard split vital and non-vital circuits, concentrating all the non-vital relays for indications and route availability for the entire area in Reading PSB but with the vital relays associated with the interlockings (SIL4) being in both the local and remote relay rooms. The WR-designed Sodeco train describer equipment used PO 3000 relay sets with the description and stepping storage facility contained within the berth display mechanisms.
The PSB was later extended to include the Twyford area including Henley. In the 1970s, a separate panel was provided to control outwards along the Berks & Hants to the outskirts of Westbury. The TD equipment was renewed twice, firstly to replace the electro-mechanical storage and stepping with electronic displays, and then in around 1990 with a VDU-based system to facilitate a link to the Cab Secure Radio (CSR) then being introduced on the suburban services. The SPT system was later put onto conventional concentrators leaving the upright part of the panel as a mounting plate for miscellaneous items of equipment.
TDM systems to control the remote relay room operation were a mixture of Westronic F1 and AP Electronics products. Override controls – for use in the event of TDM failure – were carried by reed FDM circuits directly on cable pairs. An emergency control panel existed in Newbury relay room. The Didcot area was removed from Reading in 1994 and transferred to Swindon B IECC as part of the work to enhance capacity for coal trains feeding Didcot power station from Avonmouth.
The Thames Valley Signalling Centre
With Reading PSB coming to the end of its economic life, renewal would have to be considered regardless of the remodelling project. To facilitate this, the Thames Valley Signalling Centre (TVSC) was built by Spencer in the north part of the Didcot triangle and construction work was finished by March 2009. Cable route work was undertaken by Birse. The building is similar to those recently commissioned in the East Midlands (Derby) and West of Scotland (Cowlairs).
TVSC will use the latest proven signalling technology. Contracts were awarded from 2008, notably including –
•       Invensys Rail – for the signalling system design, provision of electronic interlockings and data preparation, remote control equipment to outstations and testing & commissioning activities
•       VolkerFitzpatrick – as a main subcontractor to Invensys – for cable routes, under-track crossings, cable laying and jointing, REBs, power supplies and location bases
•       DeltaRail – for the Integrated Electronic Control Centre (IECC) including the interface for re-control of remote relay rooms, signallers’ workstations and associated testing
•       Siemens – for a new SPT system
•       Invensys Rail – as a separate contract for modifications to the CSR coverage and new control console equipment.
Following extensive trials and rehearsals over the preceding six months, the first stage involved the transfer from Reading PSB of the western section of the Berks & Hants line on 21st March 2010. This initial migration to TVSC was extremely complex as all the existing signalling equipment remained and difficult interfaces needed to be designed to integrate it with the new technology.
Reading’s signalling scheme
Central to the project are three Westlock electronic interlockings. These have the same fundamental data structure as the Solid State Interlocking (SSI) developed by BR and partners in the 1980s. The Westlock Central Interlocking Processors (CIPs) are more powerful than SSI but still operate on the ‘two out of three’ principle. The trackside equipment modules for the control of points, signals etc in the Reading area remain the original design developed for SSI and thus the Westlock CIP equipment has to talk to these via up to four trackside interface modules (TIFs) per CIP. Eventually a new standard design for trackside modules will emerge, enabling a direct connection to the Westlock equipment. The TIFs can then be removed.
The Westlocks have replaced the relay equipment at Reading Station, Reading West and Spur Junction and reproduce their original interlocking. The new trackside modules work the existing point machines (including HPSS, HW, HB and Clamp Lock), as well as lineside and shunt signals of many vintages. All the remaining 17 relay interlockings covering the Berks & Hants line, Cholsey to Scours Lane, Southcote and Oxford Road, Sonning to Ruscombe and Henley remain in service but have their control transferred to TVSC. This again has been a challenge for interface design. New TDM links have been provided to all these interlockings using the Westronic 1024 system and borne upon the Fixed Transmission Network (FTN) to link to TVSC. FTN has the added advantage of resilience with diverse routing between all its nodes.
Also borne by the FTN are independent Invensys 8-bit TDM systems to all the remote relay rooms to replace the old reed circuits. These carry miscellaneous indications such as power generator alarms, for display on a mini panel underneath the monitors at TVSC. They also carry an emergency ‘force back to red’ command for signals in each interlocking area and replicate the old override facilities. Similar 8-bit TDM systems are used for emergency alarms between TVSC and the fringe boxes, proving simple to install and commission, in great contrast to the relay methodology of yesteryear. Invensys Rail has renewed the train describers at the various fringe boxes to TVSC to make these compatible with FTN transmission, including one at Reading PSB for its last nine months of service, since recovered for use elsewhere.
In TVSC, DeltaRail has provided two IECCs. There are three signaller workstations for IECC A controlling the route from Ruscombe to Cholsey including Reading Station and the Southern lines connection, and one for IECC B controlling the Berks & Hants. TVSC fringes to signalling centres at Swindon B (controlling the Didcot area), Westbury, Wokingham, Slough and Basingstoke. Due to the unusual separation of vital and non-vital functionality, DeltaRail had to develop a new ‘personality module’ in software for their Relay Interlocking Interface (RII) to replicate the non-vital relay functions.
The signallers’ workstations are similar to those in other IECCs and consist of a monitor screen with a tracker ball for route setting. In addition, big monitors have been provided above the workstation screens to display a ‘superview’ of the Reading Station area. The TD is an integral part of the IECC. Automatic Route Setting is provided for the entire area which needed Train Operated Route Release to be implemented within the RII. A new SPT concentrator using a Siemens HiPath switch with touch screens on the signallers’ desks uses the FTN to connect to the existing SPTs except for 94 new telephones around Reading Station. New or relocated CSR screens and associated equipment cubicles have been installed at TVSC. These connect via FTN to a mixture of new and altered external radio base stations positioned to tailor radio coverage to the revised areas of signaller control.
Clearly this is a multi-discipline and extremely complex project. Until the remodelling is complete, many derogations to perpetuate former interlocking principles have been required. Safety cases have been needed for various items notably the integration of IECC with Westlock. To ensure the best possible teamwork, Network Rail established a project office at Reading to accommodate the project managers and engineers of all parties. Much of the initial design was undertaken by Infotech in Hyderabad and Invensys has used all of its UK offices to work on particular elements of the project according to the necessary skillsets. Network Rail has required all contractors to attend the regular project meetings in line with its policy of directly controlling major projects of this type.
Christmas 2010
The ‘big bang’ changeover was preceded by an extensive pre-test and rehearsal programme that started in 2009 and involved most weekends during 2010. In the areas to be re-controlled, connectors were inserted to facilitate the changeover of control between Reading PSB and TVSC and the subsequent trials to integrate with DeltaRail’s RII. Temporary transmission circuits were needed if the new FTN links were not yet ready.
In the Reading Westlock area, disconnection boxes were installed trackside to facilitate the changeover of signal and point control. A series of stages migrated the majority of the point detection circuitry and some of the track circuits to new trackside locations to vacate sites likely to be in conflict with the remodelling proposals. Thus, prior to the commissioning, almost all the track circuits were indicating on the technicians’ display system at TVSC with the majority of points showing detection if the control from Reading panel was in correspondence with the Westlocks’ data. On the commissioning shifts, the changeover merely involved connecting the point motors to TVSC-control followed by a brief correspondence test.
Signals could only be connected to TVSC during the weekend possessions, so not permanently indicated at TVSC. However all but one of the signals fitted with Automatic Train Protection had already been transferred to use its new encoder during enabling stagework. Correspondence checking of the signals formed the major significant part of the Christmas workload, since all the head transformers needed readjusting to set the lamp voltages correctly. The signals’ head wiring and cabling varied tremendously but the preliminary rehearsals had given warning of such problems. The compact nature of the site gave an added complication, often preventing work being done on more than one signal at once.
It would be untrue to say that every element of this rehearsal programme worked perfectly as problems were bound to arise with such a complex set of interfaces. However that is what a pre-test is for and by the time December arrived, all parties were confident that the changeover would be a success.
The actual commissioning possession began in the late evening of Christmas Eve with a total blockade of the Reading area. An army of engineers, technicians and testers from all involved parties worked in sub-zero temperatures right through the Christmas holiday and the changeover was duly completed at 04:55 on 30th December. The signalling work was deliberately planned to happen before the Caversham Road bridge renewal so that no conflict of events and priorities would occur. The bridge work then started and was itself completed ahead of time. During this period, a restricted train service operated through Reading, using only Platform 4 and associated bays. This enabled the signallers, who had previously had some IECC simulator training, to gain some familiarity with the real thing before 4th January when the station became fully operational. It must be remembered that other than the removal of the former goods lines to the north of the station on the 31st July 2010, Reading’s layout is as yet unchanged.
The old PSB and adjacent telephone exchange will be demolished in late April to create space for the new platforms. Rerouting all the local telecom cables and the provision of new circuits for signalling was a major element of the project. A new exchange built by Birse is situated at Cow Lane within the Reading west triangle to serve the local telephone extensions. The scene is thus set for the remodelling to start in earnest, made much easier by having a signalling system that is flexible enough to keep pace with all the ensuing changes.
Future plans
The TVSC at Didcot has not been provided solely for this project. Crossrail will, of course, impact on GW operations. The present ‘Slough New’ signalling centre does not have the capacity to control the proposed layout between Paddington and West Drayton so this area will transfer to TVSC in December 2011. Thereafter it would be logical to abolish the gate boxes at Colthrop and Kintbury, giving direct control of all relevant crossings to TVSC via CCTV. Swindon B, currently controlling the Didcot area and west towards the old Swindon PSB, is another obvious transfer candidate; the same will eventually apply to the original Slough power box controlling Maidenhead to Langley and branches.
With the huge flexibility and resilience that the FTN transmission offers, there are now no geographical limits on the size or location of a signalling control area. This coming together of signal and telecommunications technology is paying massive dividends. What’s certain is that the industry’s team is going to be kept busy in the area for the foreseeable future.
Thanks to Peter Woodbridge of Invensys who supplied information on the signalling work, to Network Rail’s David Wilson and Harry Mercer for their help in producing this article, and to Invensys Rail and Network Rail for the photographs.
