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Training for 4LM is under way

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The resignalling (or, more correctly, re-control) of London Underground’s sub-surface lines (Metropolitan, Hammersmith & City, Circle and District) has reached the stage where training of staff has begun. This huge project, now known as the Four Lines Modernisation (4LM), had a couple of false starts which took time to resolve but, finally, the fruits of the multi-billion pound investment are emerging.

Rail Engineer visited the new Hammersmith Service Control Centre (SCC) to see first-hand what has been achieved to date and to meet with Mark Warner, the service control manager, together with members of his team, to learn some of the logistics on what is involved.

The principal contractor for the project is Thales, and members of their engineering and publicity teams were also present to explain the technical elements and the continuity that has resulted from previous contracts on the Jubilee and Northern lines.

Rail Engineer published an engineering overview of the project back in issue 132 (October 2015) and various other articles have appeared since then on different aspects of the project. The work centres around the Thales communications-based train control (CBTC) SelTrac system, which has been deployed on many metro railways around the world. First rolled out on the Vancouver Skytrain network, the system is used in the UK on the two LU lines referred to as well as the Docklands Light Railway.

Whereas these lines used track-based loop technology for control, command and positional information, the sub-surface lines will use radio technology to continually communicate with the trains together with sleeper mounted transponders (RFID TAGs) to give train position information. The radio will employ free space transmission, even in tunnels, using the 2.4GHz Wi-Fi band. This technology has already been proven in South Korea, China, Canada, America and Singapore, so deploying it in the UK is not seen as a technical risk.

The control room

It is big, but then the sub-surface lines are a lot of railway. Not yet operational, Hammersmith SCC will go live in March 2018, when the Metropolitan and District line control, currently at Baker Street, moves to Hammersmith. Arranged in a series of ‘half moon’ suites, this layout has been found to be the most practical following experience from other control room upgrades and new builds.

Each suite will have its particular responsibilities. These are:

  • Signalling – under Automatic Train Supervision (ATS), the signallers should, in theory, have little to do. However, there is a considerable amount of shared operational running that will take place both within the four sub-surface lines and, more importantly, with the Piccadilly line to Uxbridge and Network Rail lines to Amersham, Wimbledon and Richmond, so it is useful that the control system undertakes many of the routine functions allowing the signalling staff to focus on the strategic control of the service.
  • Communications and customer information – the service controller for each line also uses the workstations. They have responsibility to communicate with all stations on the four lines should any incident occur and to arrange the recovery from any problem. Supplying timely and relevant information on line performance to stations will be important as will feeding the social media networks with train service updates.
  • Train maintainer – managing the rolling stock performance is seen as very much part of the integration of the train service, hence having the control of this within the same room.
  • Service managers – two workstations that will provide the overall management control of the four lines with responsibility to make strategic decisions when any major perturbation to the service occurs.

Not included, as yet, is the civil engineering management of the lines including day-to-day maintenance of the permanent way. This will remain separate for the time being.

Every desk suite is capable of showing the complete sub-surface railway on the large screens above the workstations. However, it is unlikely that any one controller would require this view alone for their particular task and thus a ‘zoom in’ on the main system management centre workstations for specific areas of the railway will be the normal choice of view for individual controllers.

No video wall will be provided. Whilst impressive for anyone visiting the centre, these have been found to be of little value for control room staff in other places.

The desk screens, and indeed much of the hardware associated with the desk positions, are COTS (commercial off the shelf) equipment and thus moderate in price and easily upgraded or replaced should the need arise.

Interlocking and telecommunications

The entire sub-surface network will have 14 computer-based ‘interlockings’ (VCCs – Vehicle Control Centres) that dynamically manage safe separation of trains, which will be located at Hammersmith. For reliability reasons, these will be backed up by a ‘two out of three’ system, meaning that if one of the computers fails the system will still be able to run. Thus, the control of points, and other signalling equipment out on trackside, will be activated from this one location and then implemented by local signalling equipment rooms around the network, from where connections to points, axle counters and other trackside equipment will be made.

Such a configuration demands very robust telecommunications links and so every junction and point location, including those that control access to train depots, will have a diverse link back to the control centre. A new fully duplicated fibre cable network is being laid for the CBTC network.

LU has its own general-purpose fibre-based telecommunications network known as CONNECT, which was also provided by Thales a few years ago. This will be integrated into the 4LM control room and, as well as giving access to all parts of the network, it provides the backbone for the voice radio communication to the trains and handhelds.

Service control manager Mark Warner in the simulation room.
Service control manager Mark Warner in the simulation room.

Simulation room and ongoing training

The logistics that have to take place before ‘going live’ are significant. Around 200 operational staff will require to be trained on the new system, but to try and do this on the actual control consoles is impractical since it would disrupt day-to-day operation and anyway it would be impossible to replicate all the conditions likely to be encountered.

A separate training room is therefore part of the Thales contractual provision, containing identical screens and desk devices that mirror the real railway. Simulated train services provide a typical day’s operation with the controllers first learning how to manage and use all the facilities under normal conditions.

After that it gets harder, as the simulator is capable of imposing fault conditions of a bewildering variety. Every conceivable situation can be replicated and covers, amongst others, train failure, signalling system failure, station closure, passenger disruption, power failure, differing weather conditions and out-of-turn running.

The northern part of the Metropolitan line is in the Chiltern hills, where leaf fall and low adhesion can be a problem. When this occurs, different braking profiles have to be introduced, which will be part of the training regime. Alarm generation and understanding of the alarm status will be an important element of the training.

Of course, once the system goes live, a failure situation will undoubtedly occur that had not been anticipated. One description of the simulator is that it is the ‘ultimate play station’, and the product and facilities will grow as the project roll out progresses.

It is anticipated that each controller will require six or seven weeks of training and, for all the staff, this will take over three years, in line with the project programme. Re-training of controllers will be a regular requirement, particularly when new or changed facilities to the system are introduced.

Passenger information

Most stations on the sub-surface lines already have ‘next train count down screens’ on platforms and ticket halls. These will not be changed, but will have to be re-controlled from the new centre.

The fragmented signalling that currently exists is often unable to predict the next train until it is very close to the station. This is particularly true where there are flat junctions. Typical is Edgware Road (its signalling interlocking and miniature lever frame date from 1926), where the Circle and Hammersmith & City lines diverge. The next eastbound train will only display when virtually in the platform.

Once the new signalling is operational, the system will have a complete overview of train position on the railway and, coupled with the inbuilt automatic train supervision capability, much more timely information will be displayed, thus increasing customer confidence in the train service.

One oddity is at Earls Court, where the present ‘light box arrow’ indicators for the Next Train have to be retained as they are now a listed feature. To overcome this anachronism, LED displays are being mounted under the old indicator framework.

Loudspeaker audio information will be broadcast from the Hammersmith SCC, where the station systems have the functionality enabled to do so. However, local stations and control rooms, where the local staff sometimes have a better sense of immediate need, will also continue to make some announcements. Clearly, local stations will be made aware of any out-of-turn running or train delays by the central control.

Interworking with other lines

Shared operation with other lines and train services has been referred to. On most of these – from Chiswick Park to Hanger Lane (where the District line uses Piccadilly line track), London Overground from Gunnersbury to Richmond, South West Railway from Putney to Wimbledon – the SelTrac system will be overlaid on to the existing conventional signalling on these sections such that ATO can be maintained. The ATO overlay will align with the block sections of the conventional signalling so not all CBTC features, such as moving block, will be possible. However on these extremities, this is not seen as a problem since the service density is lighter.

On the Chiltern Lines from Harrow on the Hill to Amersham and Piccadilly line from Rayners Lane to Uxbridge, an ‘underlay’ system is being provided, whereby the present signalling is being replaced with a conventional three-aspect system for Chiltern trains but incorporating a blue aspect for Metropolitan line trains working in ATO mode.

The system will know which type of train is where and will display the appropriate aspect on the signal. The system will not show a blue light when either a red, yellow or green aspect is displayed and vice versa. This ‘underlay’ approach will allow following Metropolitan line trains to operate in moving block operation whilst Chiltern Line and Piccadilly line trains will remain in fixed block operation.

Train stops must be retained at all lineside signals on these routes with ‘other lines’ trains retaining associated trip-cock braking equipment.

Controllers and signallers will require a full understanding of the train services and operation on these routes with direct communication links to other signalling centres and control rooms to sort out problems as they occur.

Training the drivers In parallel with what is happening at the Control Centre, simulators are being provided at four locations – Hammersmith, Neasden, Upminster and West Kensington (Ashfield House, the main LU training centre) – to train some 1,200 drivers who operate the sub-surface lines.

The simulator equipment is provided by SYDAC, now a company within the Knorr-Bremse group, and Rail Engineer went to see the one located in an office block near to Hammersmith station. The simulator provides a full-sized S Stock cab equipped with the SelTrac train control equipment and a graphic simulation of the route ahead including signals, stations and junctions. Drivers will be trained on three modes of operation – full ATO mode, manual driving under full supervision conditions, emergency driving with the CBTC system failed.

ATO will be the normal operation, with drivers having to press two ‘start’ buttons to begin movement, whereupon the train will proceed automatically to the next station stop. Drivers will continue to be responsible for door opening and closing.

Manual mode under supervision will require drivers to operate the combined power and brake controller and drive to a movement authority indicated as a circular band around the speedometer. Should the driver exceed the permitted speed, then braking will occur automatically.

In the emergency mode, the driver will be able to move the train at a maximum 10mph, subject to the route ahead being confirmed, with points set in the correct position and in conjunction with trackside route secure indicators. Various alarm and failure conditions can be imposed, which the drivers must be able to deal with.

Two types of training will take place, firstly on the simulator and then with an instructor out on the line. Training of the trainers took place first and actual driver training began in December. The training is being phased in line with the programme for introduction of the new signalling system. First will be around 330 drivers on the Hammersmith & City and Circle lines, then some of the approximately 575 drivers on the District line who work trains to Edgware Road, after that the 330 drivers on the Metropolitan line and, finally, the remaining drivers on the District line.

Driver's cab in the simulator.
Driver’s cab in the simulator.

System introduction

Both LU and Thales are rightly cautious about introducing the CBTC operation into service. In all, there will be 15 migration stages, each one of which has to be extensively proven before going live. The first section, from Hammersmith to Latimer Road, is already under system test and running test trains under ATO with the commissioning into passenger service scheduled for mid-2018. Thereupon, the system will extend to Paddington followed by the north and then the south sides of the Circle line. Both of these sections embrace part of the District and Metropolitan lines, hence the need to have their drivers trained. Following that will be the eastern end of the District line, the Metropolitan line up to Moor Park, the western end of the District line and, finally, the rest of the Metropolitan line branches to Amersham and Uxbridge. The programme completion date is planned for 2022.

The trains also have to be fitted with the SelTrac equipment, which involves them being sent back to Bombardier at Derby. This is a 23-day process and, so far, 25 of the S7 stock have been converted and a smaller number of S8s. The migration approach requires both finished infrastructure and enough CBTC-fitted trains to run the service to be available for any section to be cut over as non-CBTC fitted trains cannot operate over the new CBTC-commissioned sections. All trains will need to retain the old trip-cock signalling system equipment, where they operate over sections still to be converted.

Whilst modernisation is long overdue for some of the equipment on the sub-surface lines, the overall objective is to get a big capacity improvement on the lines concerned. Anyone who lives or works in London will recognise this urgent need.

This article was written by Clive Kessell.

Read more: Stations – what happened in CP5 and what’s happening in CP6?


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. Interesting that TfL have once again gone with SelTrac rather than ETCS with ATO. The latter would seem more future proof and with less vendor lock-in, plus the easier extension to running mainline trains on ATO on the shared track.

    • ETCS is not a metro system and it is not (yet) available in a moving block version. In its current form it would be a major constraint on providing the 32 trains per hour throughput required.


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