A number of projects have taken place recently to abolish yet more lever frame signalboxes and mechanical signalling. Few of these remarkable survivors of nineteenth-century technology remain in main line service and it will be left to the heritage sector to ensure future generations know how signalling was achieved in the past.
One of the projects was in East Nottinghamshire, on the line from Nottingham to Grantham. Older readers will recall that this route was originally a Great Northern line (the Great Northern disappeared in 1922 – how old do you think our readers are? – Ed) and terminated at the now demolished Nottingham Victoria station. In 1967 a new connection at Netherfield enabled Grantham line trains to access Nottingham Midland station via the Lincoln route.
In 2013, Nottingham station was closed for a six week period whilst the entire layout of the station was remodelled with the signalling transferring from the 1969 Trent Power Box to the new Derby ROC.
This project extended the signalling boundary out to Lowdham fringe box on the Lincoln line and Bingham fringe box on the Grantham line, thus enabling modernisation of the route and associated level crossings in the city’s eastern suburbs. Eastwards of these locations, traditional mechanical signalling still existed including numerous level crossings. Modernisation was long overdue.
The East Notts scheme
Back in 2012, Network Rail developed a scheme based on the premise that the modular signalling solutions then coming on stream would enable a more cost effective and faster upgrade compared to conventional technology. Tenders were invited at GRIP stage 4 in the autumn of 2013, with a contract awarded in March 2014 to Signalling Solutions Ltd (SSL).
The firm had recently delivered its first modular signalling pilot project on the Ely – Norwich line. This enabled the modular approach to be developed and proven and, as a result, potential problems associated with this new and innovative approach had been identified and resolved.
New signalling was to be extended to Newark Castle on the Lincoln line and Allington Junction (close to Grantham). No permanent way alterations were envisaged other than the removal of some redundant crossovers and a new switch crossing at Newark Castle. No line speed improvements were instigated.
The signalling would be mainly two-aspect with discrete block sections but including some three-aspect signals where required. Allington Junction signalbox, commissioned in 2005 and equipped with an Entrance-Exit panel and relay interlocking, was built to accommodate the construction of a curve that eliminated a flat crossing on the ECML for trains from Grantham going towards Sleaford, Boston and Skegness.
At Newark, the Lincoln line crosses the ECML on the level with train movements being controlled from Doncaster Power Box. As such, the new signalling had to be interfaced with these controls. Derby ROC already had a Netherfield workstation under the Nottingham project with sufficient capacity to accommodate the two new lines.
Modular Signalling
The idea of modular signalling is to construct the necessary elements to a standardised design whilst also aiming to use pre-assembly and test in a factory environment to minimise the amount of installation and testing work needed on site. The East Notts project consists of:
- An interlocking using the Alstom ‘Smartlock™’ electronic product already in use at many UK locations, the first being Horsham some 10 years ago. This equipment is positioned in the Derby ROC equipment room.
- A ‘front end’ to link the signaller’s workstation and mouse to the interlocking, in this case using the well-proven Siemens (ex-Invensys) Westcad system. The two companies worked well together even though they are competitors on many occasions.
- Local Trackside Functional Modules (TFM) installed in ‘Signalling Island’ Relocatable Equipment Buildings, known as SI-REBs, located adjacent to an existing junction or level crossing. These contain all the SSI (Solid State Interlocking) modules, transformers, rectifiers and relays needed for each location.
- Local cabling out to signal points and level crossings pre-made in measured lengths with plug and socket connectors for ease of installation.
Train detection equipment using Thales AZLM type K axle counters. - A transmission link from Derby to the ‘Islands’ using the Network Rail Telecom-owned FTN network. These links are formed in rings such that any cable cut does not stop traffic being carried. ‘Points of Presence’ were established at all the SI-REB sites, from where the data streams are extracted. Alan Dick Communications (ADComms) at Scunthorpe was contracted to provide the interfaces between the FTN and the local cabling.
- LED signals supplied by Unipart-Dorman for the red, yellow and green aspects but with a single aperture that can show the three colours.
In-bearer Clamp Locks by SPX for point operation (none required on the Grantham line). - Local power supplies from the local electricity company to supply the Islands and including a battery backed Uninterruptable Power Supply (UPS) giving a four-hour duration should the mains fail plus hard standing for a generator should the outage be prolonged.
- Level crossing systems of various types, some existing and some new (see later paragraph).
Most of these piece parts can be assembled and connected off site as part of the integrity proving process.
Delivering the Grantham line
Only the Grantham line has been commissioned so far – over the weekend 27-30 November 2015. The work needed to construct and install the elements of equipment make an interesting account and demonstrate the involvement of many parties in a modern signalling scheme.
Key to any signalling project is the preparation of the control data that is loaded into the electronic interlocking – Smartlock in this instance. This task was carried out by SSL engineers from the York office and then tested at Derby.
The three REBs – at Bingham, Aslockton and Orston Lane – underwent several fit-out stages to accommodate power, lighting and signalling equipment. The REBs were made by Eldapoint of Liverpool, which provided power and lighting wiring and then transported them by lorry to Blackburn Standing of Nottingham for fitting with the power equipment and UPS. That done, they then travelled to MGB Signalling in Plymouth for fitting out with signalling equipment and racking procured jointly by SSL and MGB.
Next move for these REBs was to the SSL depot at Beeston, near Nottingham, where off-site testing could be carried out, known as a ‘hangar test’ facility. Here, by using a test Smartlock, verification testing, functional testing and principles testing can be carried out, connecting to either the signal/level crossing equipment powered up at the Beeston site or to simulations of the external kit.
Once completed, there is a high degree of confidence that the system will need only minimal on-site final testing. The equipment was then transported to the various sites and installed. Prior to this some considerable civils work had to be carried out including signal bases, REB foundations and level crossing alterations, this being contracted to Global Rail of Hatfield.
SSL used its own in-house staff for installation and for functional testing over the commissioning weekend. Bingham and Bottesford West signalboxes were closed with Allington Junction becoming a fringe to Derby ROC. The commissioning went smoothly and the line was handed back to traffic on the Monday morning as planned.
A number of modifications/improvements have been made to the SSL modular signalling system resulting from lessons learned on Ely – Norwich. These include facilitating easier fault finding and maintenance, equipment room reliability and overall system safety.
Level crossings
The Grantham line has a number of level crossings. Existing Automatic Half Barriers at Scarrington Lane and Normanton are largely unchanged (Normanton had a new signal within its strike-in point and thus needed adjustment to the control circuitry) but with their alarms and status indications now shown on the Netherfield workstation at Derby ROC.
At Bingham and Orston Lane, the manually controlled full barriers have been converted to Obstacle Detection semi-automatic operation (MCB-OD), whilst at Aslockton station, the previous AHB has been converted to an MCB-OD crossing. These use detection equipment to prove that nothing is trapped between the barriers, whence a sequence is initiated to lower them automatically and clear the protecting signals.
The detection process uses a combination of RADAR and LiDAR, the former mounted up to 915mm above rail level to scan the crossing as a general area, the latter (light detection) being two units, one at chest height, the other at near-ground level, to scan the roadway for any object that the RADAR might miss.
SSL was asked by Network Rail to manage the pilot introduction of OD technology on the Ely – Norwich project, but a key challenge was encountered with the low level LiDAR lens becoming obscured by dirt thrown up by trains and road traffic. As a result, all crossings using OD technology are risk assessed to establish if the lowest level detector is actually needed. Some light traffic crossings may be judged not to require it. Both LiDAR units are now equipped with a motorised shutter which automatically opens when the scanning process is taking place. This has solved the problem of dirt accumulation.
At Bingham, an additional safety feature has been introduced, namely Barrier Protection Management (BPM).
This comprises an inductive loop mounted in the roadway to detect if a vehicle is stopped where the barriers would come down. If activated, it stops the lowering sequence. The road here is much busier than the others and it is possible for traffic to queue across the railway. It is the first application of this feature by SSL but will be used elsewhere in similar circumstances.
Should any of the detection equipment pick up a problem, then the initiation sequence is stopped and the signaller investigates the situation, taking whatever action is needed.
Onwards to the Lincoln line
The Lincoln line will follow a similar pattern this coming autumn but with some added complications. Signalboxes at Lowdham, Fiskerton Junction, Staythorpe crossing, and Newark Castle, together with Gate Boxes at Fiskerton station and Rolleston, will be closed. The level crossings at these locations will be converted to MCB-OD operation except at Newark Castle. The barriers here are currently locally controlled from the adjacent signalbox and will be converted to remote CCTV monitoring under the control of Derby ROC.
AHBs at Gonalston and Thurgarton will stay the same but with alarms and indications sent to Derby. The AHB at Bleasby will be converted to MCB-OD operation.
With all these crossings to be altered and tested, it has been decided to commission the line in three stages, planned for September, October and November 2016, rather than having a changeover in a single weekend.
However, this does necessitate establishing temporary fringe boxes at Fiskerton Junction and Staythorpe for a short duration. The Newark flat crossing with the ECML will need an interface with Doncaster Power Box to be developed.
Lessons learned
Modular signalling can offer a much cheaper solution for secondary lines when compared to conventional signal technology. By using a state-of-the-art computer-based interlocking (CBI) like Smartlock, the system will be future proofed to accommodate ETCS. Cable lengths from the TFMs are calculated to be within limits to ensure effective immunisation for any future electrification.
This scheme has been the second modular signalling project for SSL and has enabled the company to consolidate the experience gained from the Ely to Norwich project. SSL believes it places the company in a strong position to deliver further modular-based schemes, realising re-signalling on secondary lines at a much lower cost than traditionally designed schemes.
Thanks to Andy Cokayne (project director) and James Suter (project engineer) for explaining the scheme in detail, and to Judy Viitanen for arranging the visit.
