West Midlands Resignalling

Opened in September, the imposing Birmingham New Street station, with its iconic new atrium atop the huge new concourse, has at last created space for the 175,000 passengers and visitors who pass through the station every day, up from 60,000 passengers a day that the previous 1960s rebuild was designed to accommodate.

However, down at platform level, the 1960s track layout and signalling is still in service. It was designed to cater for 650 trains a day but this has since risen to 1,200. Remarkably, this increase in train movements has been accommodated effectively with very little change to the track and signalling infrastructure.

That’s all about to change, and Rail Engineer was invited by Richard Dugdale, Network Rail’s sponsor for infrastructure renewal projects, to hear about the huge programme to renew all signalling in the West Midlands area.

Signalling programme

Network Rail’s London North West (South) Route Infrastructure Projects (Signalling) team, led by Elgan Davis, has been managing the renewal of the signalling infrastructure. The programme started with Coventry PSB area in 2007 and will be almost complete when New Street station is resignalled in December 2018. That just leaves the recontrol of Cross-City North (Aston NX panel), which has been postponed to CP6 (after 1 April 2019).

Siemens is the framework contractor for West Midlands signalling renewals and is the preferred contractor. Wolverhampton PSB resignalling was tendered before the signalling framework was in place and was won by Atkins, which sub-contracted Siemens for the signalling data build. At the time, Atkins didn’t have an interlocking/workstation product but it is understood that they are coming to market with product in partnership with GETS (now acquired by Alstom).

Early GRIP stage signalling design work is being undertaken by Network Rail’s in-house Signal Design Group (SDG). Andy Reynolds from this team was on hand to explain the various design issues described below.

WMSC takeover

The new signalling is being controlled from the WMSC (West Midlands Signalling Centre) at Saltley, originally built for the aborted West Coast Passenger Upgrade 2 (PUG2) signalling for 140mph, but now accommodating West Midlands area signalling in the high security building.

The early 1960s era of West Coast Electrification heralded a period of unprecedented infrastructure modernisation in the West Midlands. From the signalling perspective, new power signal boxes were provided at the following locations with dates of the original commissioning and subsequent resignalling to WMSC: Coventry (1962-2007), Bescot (1965-2013), Wolverhampton (1965-2015), Walsall (1965-2013), Saltley (1969-still open for residual area: cross-city south) and Birmingham New Street (1966-still fully operational).

In addition, the programme includes the resignalling of the remaining mechanical signal boxes which were left in place when the power boxes were commissioned – in the Oxley, Cannock, Wilmcote and Banbury areas. Recontrol of existing relay interlockings built more recently at Birmingham Snow Hill, Stratford-upon-Avon, and Madely Jn, and recontrol of existing SSI interlockings on routes serving Stourbridge, Longbridge and Lichfield, also form part of the project.

New Street power box

Birmingham New Street Power Signal Box, a Grade II listed building commissioned in 1966, continues to stand sentinel, overlooking the west end station throat. The extensive area of control stretches from Hampton-in-Arden in the east to Tipton in the west and embraces parts of New Street-avoiding ‘Grand Junction’ lines and the cross city route.

The intensity of train movements is such that working the NX panel is a challenging job for signallers. There is no Automatic Route Setting (ARS) or Train Operated Route Release (TORR), all routes having to be set up by pressing buttons and cancelled behind each train by pulling up the entrance button.

Capacity remains a thorny problem. Increasing the number of platforms and approach tracks in the subterranean environment would be extremely challenging and costly. Even if this was physically possible, conflicting movements at the east and west throats would limit the throughput of trains. The opening of HS2, and a possible Bordesley chord to divert some New Street services into Moor Street, will provide much needed relief.

Renewing New Street signalling

Plans are well advanced for the replacement of New Street box on a mainly like-for-like basis with, generally, all-new signalling. The original Westpac MkI & MkIIIB geographical relay interlockings will be replaced by Siemens Trackguard Westlock. Proof House Junction was resignalled in 2000 with two SSIs, and this is planned as a ‘relock’ using a single Westlock interlocking, the outdoor signalling infrastructure in this area remaining as it is now. The former New Street area will be controlled by three Siemens Westcad workstations.

Clamp locks are the preferred point operating mechanism for LNW(S). However, points will retain their existing mechanisms unless in need of renewal. Indeed, the remaining original electro-pneumatic points on the patch are being replaced with clamp locks as a separate exercise by Network Rail’s in-house works delivery teams prior to resignalling.

Where new S&C is provided, such as at Galton Junction where a track remodelling project is programmed to precede resignalling, ‘in-bearer’ clamp locks are to be installed. No changes are planned for S&C in the New Street station area as each end of the station was the subject of a big track-relaying project a few years ago.

New Street moves to WMSC

First to go, in November 2016, will be the route towards Bromsgrove as part of the wider Cross City South project. Four major New Street phases are planned to take place between December 2017 and December 2018.

• Phase 1: Cross-City South – Nov 2016;
• Phase 4: Stour Valley (Soho to Tipton) – Dec 2017, with a track remodelling at Galton Jn over Easter 2016;
• Phase 5: Grand Junction lines (Stechford to Hamstead) – Dec 2017;
• Phase 6: Birmingham International (Hampton-in-Arden to Proof House) – May 2018;
• Phase 7: Birmingham New Street Station area. The box will then close – Dec 2018.

Whilst the Dec 2017 date is secured, the later dates are, at this time, still to be agreed, with Euston HS2 enabling works competing for resources and access availability in the December 2018 timeslot. Phase 7 will mark completion of a programme of the systematic transfer of signalling to WMSC with the exception of Aston NX panel for which, at time of writing, no date has been set for recontrol.

Non-compliant layout

1960s railway engineers were faced with shoehorning the then-new modern station into the cramped site bequeathed by our Victorian predecessors. They crammed in as much track and point work and as many platforms as possible, but this inevitably forced some compromises in the signalling scheme plan.

Platform ‘starting’ signals have to be as close as possible to the end of the platforms to maximise standing room, yet immediately beyond the signals are points. When a route is set into a platform and up to the signal at the exit end, an ‘overlap’ would normally be set. The length of an overlap is specified in Railway Group Standards as 45 metres, given the blanket line speed of 10mph. Such overlaps, if provided, would lock points for 45 metres beyond the signal until such time as the incoming train has come to a stand, thereby preventing any other movements taking place using the said points.

Such operational restrictions, which would have a severe impact on capacity and hence the timetable, were deemed unacceptable in the 1960s signal design in which no overlaps were provided in the station area. There are also some compromises with regard to gauge clearances within the station throats. If this concept was to be perpetuated in the forthcoming resignalling, a much more rigorous justification would be required to obtain the necessary derogation.

The inherent lack of space at New Street also causes problems mid-platform. Back-to-back mid-platform signals are used to separate the platforms into two separate block sections, although permissive movements (more than one train occupying a block section) are sometimes necessary for which position light signals are provided. Once again, no overlaps are provided for the mid-platform signals, nor is there a separate train detection section between the signals. In 1966, trains consisted of locomotive-hauled rakes, or first generation DMUs. Today, multiple units are the order of the day and many DMUs consist of 23-metre length vehicles which are a little longer than their predecessors. In order to suit present day and foreseeable train configurations, a major exercise had to be undertaken to determine the optimum position for the mid-platform signals.

Another issue with the existing mid-platform signals is that an incoming train proceeding through to the far end of the platform may stop with its rear overhanging the mid-platform signal even though it has cleared the rear platform detection section. A second train could be signalled in on a single yellow only to be confronted by the tail-lights of the first train a metre or so before reaching the signal post of the red signal protecting the train ahead.

To address these difficult issues, Network Rail brought in Ricardo Rail (formerly Lloyd’s Register Rail) to carry out in-depth risk assessments. Operational risks to be considered include platform-train interface issues, dispatch errors, potential for overrun and SPADs, permissive working, slow speed collisions and trains not fully ‘at platform’.

Charles Stewart of Ricardo Rail elucidated the process to Rail Engineer. Under UK law, there is an obligation to show that the risk is tolerable and as low as reasonably practicable. Ordinarily, this can be substantially demonstrated by compliance with Railway Group and Network Rail standards, but the uniqueness of the arrangements at New Street precludes this approach.

Attempts to make the layout compliant didn’t progress beyond the first draft of the signal plan. Initial designs produced by SDG demonstrated that a fully-compliant solution, by putting in overlaps and/or moving signals and reducing standing room, would make the station unusable.

Historic data provides evidence that the existing arrangement has achieved an acceptable level of safety, but historic data is only an indication of what has happened and not necessarily what might happen in the future. Consequently, it cannot be assumed that a like-for-like change will be acceptably safe, and adoption of such a change would not show consideration of reasonable opportunity for improvement.

Hence the approach adopted was to consider what safety improvements were practicable to implement, taking into consideration the trade-off between safety and operability.

For example, to consider risk associated with signal overrun, RSK was employed to undertake assessments using the RSSB’s Signal Overrun Assessment Tool (SORAT) to obtain a risk score for every signal, the scores being added up to give an overall score. This exercise, using a standardised timetable, was run three times, once for the existing layout and twice for the new. The initial assessment for the new was undertaken based on SDG’s proposed design and the second based on a revised design taking into account TOC requirements for operational and stabling standage.

On balance, the new layout is lower risk than the existing one and the operational benefit from the final layout has been assessed to outweigh the slight increase in risk from the proposed design. Factors helping to improve the score include the removal of intermediate ground signals (no longer required for engine run-rounds) and a reduction in permissive working due to the mid-platform signals being repositioned to take account of today’s train length configuration, with a larger gap between.

TPWS (Train Protection and Warning System) is, of course, a feature of the station and effectiveness of the Train Stop loops (TSS) is compromised by lack of overlaps. A distance of 17 metres is required to bring a train to a stand with a TSS activation, so this has been factored into the risk assessments.

Platforms 11 and 12, which currently don’t have mid-platform signals, will have them installed on the grounds of consistency and operational flexibility.

Workstations and interlockings

All workstations are Invensys/Siemens Rail Automation Westcad. Interlockings are SSI (earlier schemes) and Siemens Trackguard Westlock. Westlock is compatible with SSI but has a much greater interlocking capacity, obviating the need for complex horizontal and vertical interlocking boundaries of adjacent interlockings. Standard SSI data links and long line links are provided as appropriate, linking to Data Link Modules (DLMs) and Track Function Modules (TFMs).

However, with Phase 6 of New Street, the plan is to move to object controllers to replace TFMs. These have the benefit of saving space (most useful at New Street where there is limited room for equipment in the confines of the station) and also interfacing directly with axle counter systems, obviating the need for interface relays and thus reducing the number of potential failure points. Object controllers are currently being trialled at Crewe.

‘Plug and Play’ was adopted for connecting external equipment in the Wolverhampton station area. This involved a significant additional design effort in determining cable lengths but this technique was a ‘one-off’ in the overall programme.

Automatic Route Setting (ARS) is not provided at any of the existing workstations at WMSC. Mick Brook, operations specialist, explained that the project is keen to get ARS in for Phase 6 (Proof House) and possibly Phase 7 (station area), to address signallers workload / workstation configuration issues. However, a problem flagged up is that TORR (a pre-requisite for ARS), will not work in the station area. The reason for this is that TORR, as currently specified, requires three changes of state (occupied/clear) of two or three track circuits, which is not possible with the mid-platform signals that have no separate overlap. However, this requirement was specified to cover ‘blipping’ track circuits. As axle counters don’t suffer from this phenomenon, it may be possible to find a safe alternative way of initiating route release under TORR.

LED signals

Lightweight LED signals are used as standard, with the supplier selected by the signalling contractor. Dorman has been the main source of supply for the schemes for which Siemens was contractor, although Variable Message Signs (VMS) signals have been installed in the Wolverhampton area.

When originally installed, a special design of compact searchlight signal, packaged within an inverted triangular box, was used on the platforms owing to restricted sighting within the low ceiling of station. However, these signals became difficult to maintain with their internal moving spectacles and comparatively poor level of brightness, and they have all been replaced over time with standard signal heads, in many cases mounted horizontally. With the potential advantage of today’s lightweight LED signals, the route asset manager has been developing a mid-platform signal to solve the various issues.

Incidentally, one important feature worth mentioning is the provision of additional and more evenly spaced signals, giving a standard three-minute headway between Euston and Wolverhampton with four-aspect signalling. Drivers have remarked on the improved sequence on the Wolverhampton portion of route already resignalled.

Train detection

Axle counters are the preferred method of train detection. For the New Street station area, though, some key issues need to be resolved – finding space to mount the heads on the complex point work and avoiding the susceptibility of ‘wheel rock’. The latter phenomenon occurs when a wheel becomes stationary over a head, potentially giving rise to a mis-count and false ‘occupied’ status.

To avoid operational delays caused by a failed section, Thales is running a trial at Coventry involving the use of a ‘supervisory’ section. For example, for three sections A, B and C, there would be a supervisory section A-C which provides an overall monitor such that, if there is a disturbance in the middle, it will do an automatic reset as long as the supervisory section is unchanged.

A further disadvantage of axle counters is that heads may need to be removed for track work. However, lower profile models such as the Thales type ‘K’ may reduce the need to remove the heads for all but intrusive work such as relaying.

For the forthcoming Bromsgrove resignalling, it was intended to use central evaluation of axle counters. That is to say, the Ethernet outputs from Thales type ‘K’ axle counter trackside units are fed into the Fixed Telecommunications Network (FTN) and received at WMSC where the evaluator units are to be based. This reduces the number of Relocatable Equipment Rooms (REBs) required outdoors and allows the technician to fault and test the equipment without leaving the signalling centre.

However, there are remote AHBs (automatic half-barrier level crossings) triggered by axle counter sections, and it was found that critical timings may not be achieved because of the timing cycles and processing time needed in passing the data to WMSC and back out to the AHBs. An alternative strategy has been devised for these crossings, which provides for the grouping of evaluators in REBs located at the AHBs.

Centralising all West Midlands signalling at Saltley, together with Network Rail’s control staff, is proving to be a very successful arrangement. However, the intention to recontrol the signalling to the recently opened Rail Operating Centre (ROC) at Rugby is not an early priority. A description of the latter will appear in a forthcoming issue of Rail Engineer.

Thanks to Richard Dugdale, Andy Reynolds, Jaspall Devsi, Mick Brook, James Knapp and Elgan Davis of Network Rail, and Charles Stewart of Ricardo Rail, for their help in preparing this article.