HomeRail NewsBalcombe signalling upgrade
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The village of Balcombe, in deepest Sussex, became famous in 2013 for the wrong reasons. This was where a drilling exercise for the possible extraction of oil by fracking caused a local furore and, following the resultant publicity given to the real fears of the local population, the rent-a-mob brigade descended en masse by train to Balcombe station with all the ensuing policing challenges. Little did these hordes realise that the railway route through Balcombe was already giving Network Rail and the TOCs a major headache.

The Brighton line between Balcombe Tunnel Junction and Copyhold Junction is the southern equivalent of the Welwyn bottleneck on the East Coast main line. From just south of Three Bridges, the line reduces from four tracks to two through the tunnel and then over the Ouse Valley viaduct before opening out again to four tracks into Haywards Heath station.

The line was resignalled in 1982 under the control of the new Three Bridges Power Box, which covers from Croydon to Brighton with fringe boxes on the various branches. The technology used route relay interlockings, tungsten bulb signals, reed track circuits and a traditional FDM (frequency division multiplex) system for remote control of the relay rooms and indications.

The twin-track sections at Balcombe and between Haywards Heath and Preston Park, near to Brighton, were equipped with SIMBIDS (Simplified Bi-Directional Signalling) as a means of allowing trains to run on the wrong line under restricted long block section conditions. This proved to be troublesome and had adverse safety implications as it was not possible to inform staff reliably that trains were running ‘wrong road’. The facility was therefore never properly used. Now over thirty years old, the general condition of the signalling is showing its age and renewal is pending.

The Balcombe problem and contract

The Balcombe area suffers from capacity issues and increasing capacity to six trains an hour in bi-directional travel has been essential to meet the increasing demands of the infrastructure but also to increase access to undertake essential infrastructure maintenance throughout the route without the need to disrupt large sections of the Railway.

Balcombe tunnel, is very wet and in poor condition. In recent times, masonry falls have needed urgent attention with the line being closed for lengthy periods, resulting in considerable disruption to train services with a lengthy diversion for through services or bus substitution. A metal shielding has been attached to the tunnel roof, primarily to divert water away from the tracks and into the drainage channels and also to provide some protection against any further masonry dislodgement.

The result is a decision to resignal this section of line to permit full reversible working and to provide more resilient equipment against the effects of lying ground water. It also will allow six trains an hour in each direction when reversible signalling is in operation and permit access to undertake essential infrastructure maintenance across the route without the need to disrupt this section of railway in its entirety.

The development of the scheme has been protracted with a number of false starts. Since the project involved only a partial resignalling, with the interlockings at Three Bridges and Haywards Heath being retained, the design work would have to delve into existing records in order to modify the relay circuitry.

A contract to carry out the work was awarded to Kier as main contractor. Although a new name in signalling, the company has, in fact, a depth of experience in the discipline following its acquisition of May Gurney. The company has also undertaken signalling projects in East Anglia, namely Ely West Curve, Bury St Edmonds to Chippenham Junction, Ely to Peterborough track circuit replacement and Kings Lynn signalling renewals.

TB84locs [online]

Although Kier has a growing in-house design resource, it also partners with other companies to provide additional expertise. One such relationship is with TICS Rail Signalling, based in Doncaster. Having worked together on various projects for nine years, the combined skills of Kier and TICS allow them to provide an enhanced product capable of tackling much larger signalling renewals schemes, offering Network Rail a combined signalling design facility, signalling installation delivery units and the substantial works testing teams provided by TICS.

Rail Engineer met the Kier signalling team in the impressive headquarters at Tempsford Hall, near Sandy in Bedfordshire, together with Mark Cusack of TICS, to learn how the Balcombe project has progressed.

The work entailed

In letting the contract to permit full reversible working on both lines, Network Rail originally anticipated that only the track circuits and signal heads, and the associated wiring, would need replacing with the trackside location cases themselves being reused. However, a detailed survey showed that this was not feasible and thus the scheme was expanded to a complete renewal of equipment over the 9km section. The track layout is unchanged and thus the existing point machines were kept and also some signal gantries.

Renewals include:

Replacement of all signal heads and banner repeaters with LED equivalents supplied by Unipart Dorman;

  • New signals installed for full reversible working;
  • Upgrading existing signal gantries to modern standards with ladders and walkways;
  • Provision of new lightweight signal posts and gantries supplied by Collis Engineering;
  • Embankment retention work and trough route upgrade where necessary;
  • Replacement of track circuits with Bombardier TI21 (EBI Track 200) type;
  • Additional TPWS loops supplied by Vortok;
  • Renewal of the FDM system with Siemens Westplex vital transmission system;
  • A new control panel and mimic display section in Three Bridges PSB supplied by TEW Group (now part of LB Foster);
  • New copper lineside cabling and, where necessary, new lineside locations;
  • Upgrade to the lineside 650V power supply distribution;
  • Modifications to the telecom facilities for additional SPTs and a new bearer for the Westplex remote control system;
  • Modification to impedance bonds for traction return current and associated bonding;
  • Provision of a dual train detection system in Balcombe tunnel using Frauscher axle counters.

Some of these require further explanation. The Westplex remote control system is a relatively new product. It allows vital controls and indications to be interfaced directly from lineside to an interlocking and, as such, is type approved to a SIL4 standard. This allows significant saving in signalling multicore cables and, although some initial problems were found with the connectors, a revised design overcame this.

The Vortok AWS product is much lighter and easier to fasten to sleepers than previous types, which proved itself with limited availiable track access. Some reliability problems had been encountered when used in the past which delayed safety approval, but this has now been resolved.

Power supply design has followed the now- standard Class II principle of using a double- insulated two-core ‘earth free’ cable system. Power comes from the traction sub-stations at Ouse Valley and Balcombe Tunnel Junction where two 25kVA transformers produce a main and standby 650V lineside feeder that will permit uninterrupted operation. A transformer and rectifier in each location case gives the 110V AC and 50V DC supplies for the S&T equipment.

Whilst the EBI Track 200 track circuit is very reliable, wet conditions could cause failure and thus Network Rail requested that a dual train detection system be provided in Balcombe Tunnel. The result was a parallel axle counter system that can only be switched in by the TCO (Train Control Officer) at Three Bridges. A rigorous procedure is needed for a changeover with all train movements stopped, all routes released and the necessary paperwork completed. Maybe reliability justifies this duplication.

Power box mimic diagrams are notoriously difficult to modify when alterations are needed and Three Bridges was no exception. Supplied originally by Westinghouse, the panel is made up of large square tiles, each with the tracks and associated displays for route setting and track occupation. It was impractical to modify the existing section of panel so the decision was made to lower this to ground level and install a completely new panel in the vacant position, thus allowing it to be fitted out and energised with the reversible signalling but covered up so it would not distract the signallers.

The Westplex allowed testing to be carried out direct from the external equipment to the mimic diagram. Upon changeover, the old panel was duly covered up and the new one unmasked. Co-operation with the operating floor staff, both Network Rail and the train operators, has been excellent and was instrumental in facilitating the change.

T306andT308signalGantry(2) [online]

Staging and commissioning

The Brighton main line is a busy stretch of railway so obtaining access and possessions has been an ever-present challenge. An added complication was the work being carried out to build the new Thameslink train depot at Three Bridges and S&C work at Haywards Heath. The various project teams worked collaboratively to resolve access issues and, whenever possible, both projects took advantage of the same possessions.

The new location cases and signal heads were assembled off site by Unipart Dorman and tested by TICS. Installation work proceeded during 2014 with a number of commissioning stages arranged for the autumn of that year. These included:

  • Stages 1 (part) and 4 (part) from 27 September to 6 October with 26 and 52-hour weekend possessions – power changes at Haywards Heath and Copyhold Junction and renewal of signal heads and complex looping alterations to existing circuitry within the Three Bridges interlocking (the power work had implications beyond the immediate area and affected fringe box operation at Lewes and Lancin);
  • Stages 1 (part) and 4 (part) from 11-13 October with 52-hour possession – further signal head changeover and fitment of new control panel and mimic diagram at Three Bridges;
  • Stages 3 and 4 (part) from 18 – 20 October with 26-hour possession – final fitting of new signal heads plus track circuits and TPWS fitting in Haywards Heath area;
  • Stage 5 (part) from 20-23 March 2015 with 52-hour possession – final track circuit fitment and commissioning of new signalling in the normal running direction;
  • Stage 5 (part) from 27-30 March with 52- hour possession for commissioning of the reversible signalling and test train running.
  • Shorter possessions were arranged at night for the laying of cable, installation of locations and other work away from the running rails.

The commissioning stages in March 2015 follows the serious delays to signalling works over Christmas and Network Rail put mitigation measures in place by appointing a peer reviewer to make sure something similar did not occur at Balcombe. Part of the process was a day-long risk assessment session with all contractors present to thrash out all the ‘what ifs’. This proved extremely useful and enabled teams to be formed of people with compatible and complementary skills as well as briefing everyone on access points, safety, timings and work packages.

A further stage 6, which will bring in to service the parallel axle counter protection, is due for completion later this year.

The result

The original contract value was circa £10 million and for Kier, working on such a busy and publicity sensitive main line, any setbacks would have been high profile. However the success of the project was secured by the collaborative spirit and close working relationships between each part of the team. Certainly, management of both Kier and TICS were pleased with the result.

The Brighton line now has a degree of resilience for this sensitive section. There is continuing talk of an alternative route to Brighton, possibly by the re-opening of the Uckfield to Lewes section, which seems to be gaining some momentum. Otherwise it is the long hike round by Littlehampton that almost doubles the journey time. We shall have to wait and see.

Thanks to Andrew Swanson, Paul Cornelius and Jane Mason from Kier and to Mark Cusack and John Storer from TICS for their detailed explanation of what was involved and for the honesty in portraying the real issues.

Clive Kessell
Clive Kessellhttp://therailengineer.com
SPECIALIST AREAS Signalling and telecommunications, traffic management, digital railway Clive Kessell joined British Rail as an Engineering Student in 1961 and graduated via a thin sandwich course in Electrical Engineering from City University, London. He has been involved in railway telecommunications and signalling for his whole working life. He made telecommunications his primary expertise and became responsible for the roll out of Cab Secure Radio and the National Radio Network during the 1970s. He became Telecommunications Engineer for the Southern Region in 1979 and for all of BR in 1984. Appointed Director, Engineering of BR Telecommunications in 1990, Clive moved to Racal in 1995 with privatisation and became Director, Engineering Services for Racal Fieldforce in 1999. He left mainstream employment in 2001 but still offers consultancy services to the rail industry through Centuria Comrail Ltd. Clive has also been heavily involved with various railway industry bodies. He was President of the Institution of Railway Signal Engineers (IRSE) in 1999/2000 and Chairman of the Railway Engineers Forum (REF) from 2003 to 2007. He continues as a member of the IRSE International Technical Committee and is also a Liveryman of the Worshipful Company of Information Technologists. A chartered engineer, Clive has presented many technical papers over the past 30 years and his wide experience has allowed him to write on a wide range of topics for Rail Engineer since 2007.


  1. Coming to this somewhat late(!), I found this an interesting article – but spoiled by the unnecessary and irrelevant pejorative comments about people protesting against fracking at Balcombe.

    This is a perfectly legal activity and one which, as I’m sure the author is well aware, can be viewed as increasingly necessary in an era where action to mitigate global warming appears to be honoured by government more in the breach than in reality.


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