Bristol area signalling renewals

In service for nearly forty decades, the iconic InterCity 125 High Speed Trains (HST) are soon to step back from front line service as the new electric twenty-first-century state of the art Hitachi Class 800/801 Intercity Express Programme (IEP) trains take over on the Western Route main lines.

Network Rail’s ‘The Greater West’ programme is a multi-disciplinary investment programme to prepare the infrastructure from Maidenhead to Swansea. The programme is split into three separately managed geographical areas – Thames Valley, West of England and South Wales.

Rail Engineer recently met up with Andy Haynes, project director for the West of England area, to hear about his £250 million project portfolio. Senior project engineer Matthew Spencer was on hand to explain the finer points of the signalling work.

The West of England area includes the m ain line from Swindon through Bristol Parkway to Patchway and the approach to the Severn Tunnel, Swindon to Bristol Temple Meads via Bath, plus the route between Bristol Parkway and Bristol Temple Meads. It is controlled by the former Swindon, and existing Bristol Temple Meads panel signal boxes. The signalling system has to be immunised against the effects of electric traction but, as most of equipment is now well over forty years old, the opportunity is being taken to replace much of the equipment.

The Swindon Area Signalling Renewals scheme was completed in February this year with the closure of the Panel there. The equipment was renewed on the same basis as described below for Bristol.

Incidentally, the project to remove the defunct Swindon signalling panel to Didcot Railway Centre, described in issue 131 (September 2015), was safely executed last April by the Swindon Panel Preservation Society, thereby preserving a working example of the historic BR Western Region- style of turn-push entrance-exit signalling control panel.

Bristol Panel box

The Bristol Panel box was opened in March 1970 with the ‘Main’ panel controlling from near Chippenham, through Temple Meads and onwards to just beyond Bridgwater, including the Weston-Super-Mare loop. A smaller ‘Stoke’ panel was added in 1971, controlling the South Wales main line from west of Wootton Bassett through Bristol Parkway towards the Severn Tunnel plus the section from Parkway through Filton Abbey Wood towards Temple Meads.

The lines being electrified embrace most of the main lines on the Bristol Panel, ending at Temple Meads. There are no proposals to electrify beyond Temple Meads, so there is no technical requirement to immunise the signalling beyond, but it makes sense to extend the new signalling to Parson Street Jn, the junction for the Portbury Dock freight line and soon to be reopened passenger line to Portishead. However, this leaves the route south of Temple Meads, which will remain to be signalled by Bristol Panel for the moment.

The work being managed by Andy’s team, under the auspices of the Bristol Area Signalling Renewals and Enhancements (BASRE) programme, involves 711 signalling equivalent units (SEUs) and is the biggest recontrol and relock exercise in the country.

BASRE compliance approach

The philosophy being adopted by BASRE is not one of complete resignalling. That would involve drawing up a signalling scheme plan from scratch, ensuring that the layout of signals complies with current standards and replacing everything including equipment on the track – signals, points, AWS, TPWS and ATP.

Finalising a new scheme plan takes much time and effort, involving many stakeholders including TOCs and FOCs.

Furthermore, any redesign of the signal layout would, in order to obtain capacity improvements, need to be re-visited prior to the introduction of ETCS.

Traditionally, trains are brought to a stand by the driver who, having observed a caution aspect and by using route knowledge and experience, brakes safely to a halt at the next red signal. With ETCS, it is the on-board computer that calculates and implements the braking curve. The consequence is that the ETCS block markers (equivalent to a traditional stop signal) do not have to be spaced apart to provide the necessary braking distance. With this constraint on signal positioning removed, as many block markers may be installed as necessary to protect junctions and station platforms, facilitating ‘closing-up’ and thereby improving flexibility, headway and capacity.

With large volumes of signalling work proceeding all over the country, as well as on the Western Route, signal engineering design resources are under pressure. Given the need for the signalling work to keep pace with the electrification project, an alternative solution has been adopted. It was successfully argued that, as the existing layout has operated safely for 40 years, and on the basis of no initial step change in the timetable, it is sufficient to relock the existing layout with only limited renewal of lineside assets where justified by asset condition, electrification immunisation, or reliability improvements. The existing relay interlockings, of Western Region ‘E10K’ type, would be replaced by a computer-based equivalent, of which more in a moment. Resignalling to modern standards is, however, planned for Bristol Parkway/Filton Bank/Bristol East Jn and will be completed before the new IEP service commences with the December 2018 timetable.

Complex scope

The elements of the signalling renewal are:

» Recontrol of the layout to Thames Valley Signalling Centre (TVSC);

» Replacement of WR E10K relay interlockings with Alstom Smartlock 400 computer-based interlockings (CBI) situated at TVSC;

» Provision of DeltaRail IECC Scalable signaller interface workstations;

» Classic Solid State Interlocking (SSI) Track Function Modules (TFM) controlling trackside equipment;

» SSI data links connecting TVSC with TFMs via long-line data links using the Fixed Telecomms Network (FTN) interfaced by long distance terminals (LDT);

» An uplift to the FTN network to accommodate the required SSI data capacity;

» New lineside equipment location cases with new tail cables;

»  New 650V DC signalling lineside power supply;

»  Lineside cable route: one third reused, one third refurbished, one third new;

»  Track circuits replaced with Thales AzLM axle counters;

»  All signal heads changed to LED type (mostly Dorman with the odd VMS banner repeater) by maintenance delivery team;

»  Non-immune point machines replaced by maintenance delivery team.

A collaborative working arrangement exists between the contractors, with project managers and engineers co-located at Bristol Temple Point. Network Rail, Alstom and Telent have a depot and yard here for storage of materials. The contractors are:

» Alstom is the main (framework) contractor, supplying signalling and signalling power supplies;

»  DeltaRail for the Integrated Electronic Control Centre (IECC) Scalable and signaller simulations;

»  Telent for implementing telecoms equipment including the FTN upgrade;

»  Thales for supply of axle counters;

»  Network Rail Telecoms (NRT) designing telecoms requirements;

»  Network Rail Signal Design Group (SDG) developing the signalling scheme;

»  Network Rail’s Bristol Maintenance Delivery unit, led by Roy Evans.

The new LED signal heads are being placed on the existing signal structures where possible, provided the structure is sound, is not in the way of or has sighting issues relating to the Overhead Line Equipment (OLE), and still has at least fifteen years life remaining.

This approach also saves the cost of putting up brand new signal structures that will only become redundant when all trains are fitted and operating with ETCS. Some new structures have been provided, but the policy has been to minimise the use of huge structures by exploiting the Dorman lightweight fold- down signal product that doesn’t need an access ladder.

An existing gantry at Parkway would have been foul of the OLE and has been replaced with a new immunised equivalent. The bi-directional signals, located on the right hand side of the line, have been retained.

As an aside, in the Swindon panel area, bi-directional signals were originally placed on cantilever structures in order that the aspect be displayed to the left of the driver. These structures are unsuitable for electrification and have now been replaced with single post signals on the right as per the Bristol area.

Automatic Warning System (AWS), Train Protection Warning System (TPWS) and Automatic Train Protection (ATP) track equipment remains as now, albeit with new cables wired to new apparatus location cases associated with the Smartlock TFMs. The Great Western is one of the two ATP trial sites from the 1990s – it will remain in service until superseded by ETCS. ATP is provided between Paddington and Bristol Parkway, and via Bath to just east of Temple Meads.

More than just a relock

Replacing the existing interlockings by Smartlock has the benefit that any subsequent layout alteration, resignalling or introduction of ETCS can be effected simply by making appropriate data changes to the CBI.

With a relay-based system, this would involve extremely complex wiring alterations, not least because the locking would have to be brought into compliance with modern standards.

However, some alterations are being made to the existing layout design including the significant changes described below.

The introduction of the IEP depot at the former site of Filton Tip requires two new connections. The main depot entrance connection will lead off the Avonmouth branch whilst the exit will be onto the Down Tunnel line and will be accompanied by a mainline crossover between the Down and Up Tunnel lines to enable access to platforms at Parkway. This, together with the re-quadrupling of the Filton bank line and remodelling of Bristol East Jn and Bristol Parkway, all to modern standards, provides the capacity and resilience for the December 2018 timetable.

At Bristol Temple Meads, an unusual feature of the existing layout is the provision of ten St Andrew’s crosses, effectively splitting the through platforms into two. They are actually black crosses on a permanently illuminated background within a red case suspended from the station roof that act as car-stop marker for drivers.

When setting a route into a platform, the signaller has a choice of mid- platform or end of platform exit button to press. Through platforms are allocated separate numbers for each section and the actual exit button pressed will illuminate the platform number on the signal, thus advising the driver whether the train should stop at the St Andrew’s cross or continue along the full length of the platform.

The disadvantage of this arrangement is that, even if the signaller sets the route to a St Andrew’s cross, the route is actually set and locked for the full length of the platform, including overlap at the far end which may restrict other movements.

Secondly, this arrangement is not covered by standard signalling principles and could lead to confusion if the platform number displayed is contrary to what is expected or not correctly interpreted.

Accordingly, this arrangement is not being perpetuated. All ten crosses will be replaced with back-to-back signals with position lights, meaning that each half platform will be fully signalled and so providing a safer and preferred design solution whilst allowing the existing service to operate. The position of some of the new platform sharing signals are being moved from the cross positions to suit present day train working and in anticipation of the IEP service.

New Warner routes (delayed yellow) with zero overlaps are being provided up to the platform sharing signals if the far platform is occupied. If the far platform is clear, a main route will be given with a reduced overlap using the free platform.

Clifton Down station is a passing place on the single line to Severn Beach. A new fixed red signal is being provided for Up direction moves into Platform 2, and two existing signals have been moved, allowing trains from Bristol to turn-back at this station, a movement desired by the TOC but not previously available.
Charfield loops are to be upgraded for passenger moves incorporating full overlap protection and the removal of permissive working.

Project phases

The project is being delivered in several stages (see map above):

»  August 2016 – Filton diamond relock and recontrol to TVSC;

»  February 2017 – Badminton line relock and recontrol, Stoke panel at Bristol defunct;

»  November 2017 – Bristol Parkway resignalled in new layout configuration with a new platform;

»  April 2018 – Bristol Temple Meads relock and recontrol to TVSC;

»  December 2018 – new platform brought into service at Filton Abbey Wood and new signalling with re- quadrupling between Dr Days Jn and Filton Abbey Wood, new IEP timetable commences;

»  April 2019 – Bath corridor relock and recontrol to TVSC;

»  Control Period 6 – possible remodelling of Bristol East Jn.

On completion of this work, Bristol Panel remains in service with just the south line from Parson Street towards Taunton. There is a plan to re-open the original terminal platforms at Temple Meads to provide more general capacity for trains terminating here, but the Panel Box occupies the throat. To decommission the panel, proposals are in hand to recontrol Bristol south area to TVSC in CP6 after 2019.

In addition, an FTN node is located within the box and would need to be relocated. There are also plans for a Bristol Metro, of which Stage 1 (service to Portishead branch) can be accommodated within the existing layout. Future phases will be helped by the proposed remodelling of Bristol East Jn.

Further west, plans are afoot to resignal Cornwall and provide capacity for a half-hourly service between Plymouth and Penzance. This is expected towards the end of CP5 and on into CP6.

When is a ROC not a ROC?

Network Rail’s National Operating Strategy lists TVSC as a Rail Operating Centre (ROC). However, the two-story building tucked away in a constrained site at Didcot was built as a signalling centre before the concept of the national ROCs was announced. Work continues apace to recontrol the Western Route signalling from life expired boxes and to date Paddington to Swindon is currently controlled with Bristol coming on stream as described above. The Oxford area is also being prepared for transfer.

TVSC does not have all the facilities in the ROC specification, nor is there currently space in the building to accommodate Network Rail’s Route controllers who are based in Swindon. So it remains to be seen how TVSC is upgraded to become a ROC.

TVSC exclusively uses the DeltaRail IECC signaller interface. The Swindon area was commissioned with IECC Scalable (issue 92, June 2012) as will Bristol, whilst the existing classic IECC workstations are gradually being converted – Reading has recently been upgraded. Interlockings are a mixture of Siemens Westlock and Alstom Smartlock 400. FTN is the carrier for SSI data links from TVSC to TFMs on site.

Thanks to project director Andy Haynes, senior project engineer Matthew Spencer, TVSC operations manager Simon Ponter, local operations manager Graham Wells and control centre technician John Kai Kenyon-Noquet for their help in the preparation of this article.

Written by David Bickell.