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Communications Based Train Control

Communications Based Train Control (CBTC) means different things to different people, so says Tom Lee from the Rail Standards and Safety Board who chaired a recent conference in London on the subject organised by Sagacity Media. The engineering / technical aspects are often not seen in the context of operations or passenger service and, whilst CBTC systems are becoming more widespread, they will never be a mass market offering such as road vehicles and public communication networks.

The mix of capacity and energy usage is crucial and far too many examples exist of trains transporting fresh air around for parts of the day. Availability and reliability go alongside safety and using proven technology is often best – being the second application might be preferable but remember someone has to innovate.

So what is CBTC, what does it offer and where are the shortfalls? A number of speakers attempted to provide the answers.

History, standards and broad perspective

David Dimmer, from Thales but working for European railway industry association UNIFE on its NGTC (Next Generation Train Control) project, started the conference off. He commented that, whilst most people associate CBTC with urban metros, it can also embrace ERTMS (European Rail Traffic Management System) technology, particularly where this will be used in high density urban operations.

The technology really began back in the 1960s with the opening of London’s Victoria line, but CBTC only became a recognised terminology in the 1980s. At that time it used track loops as the transmission method although radio became the natural choice in the 1990s.

CBTC consists of three elements – ATP (Automatic Train Protection), ATO (Automatic Train Operation) and ATS (Automatic Train Supervision). Attempts to standardise the functionality and technology have had mixed success. Results so far include:

  • IEEE 1474.1 – Functional and Performance Requirements
  • IEEE 1474.2 – User Interfaces
  • IEEE 1471.3 – Recommended Practice for System Design
  • IEEE 1474.4 – Recommended Practice for Functional Testing.

None of these are mandatory and fall way short of getting standardisation in equipment practice. The intended specification IEC 62290 ‘Urban Guided Transport Management – Command and Control’ has too large a scope, thus making little progress. The ModUrban project had an objective to create an interoperability specification but this was not achieved other than a definition of system architecture. Nonetheless the need very much exists and in New York, as an example, the operator has demanded inter-equipment testing from two suppliers.

The NGTC project started in 2012 with a budget of €11 million aiming to produce a European standard that embraces ATO, DTO (Driverless Train Operation) and UTO (Unattended Train Operation) requirements. Its 21 members comprise UNIFE, manufacturers, operators – including London Underground and Paris Metro’s RATP, the ETCS (European Train Control System) Users Group together with various universities and consultants. It sees a growing commonality between CBTC and main line technology, setting out tasks as a series of work packages. These include: technical coherence, common message structure, moving block requirements, IP-based radio communication beyond GSM-R and satellite train positioning (main line applicability only). The focus appears to be on merging ETCS and CBTC technology; perhaps not the right priority at the present time.

It might be concluded that CBTC is more a broad conception rather than a specified technical and operating system. This creates uncertainty  amongst both existing and potential users as to what type of system to choose and how much to specify.

The London Underground vision

LU has had a somewhat mixed experience of CBTC over the past few years. The first application (although not known as CBTC in those days) was the use of Automatic Train Operation in the 1960s on the then new Victoria Line. Designed in house, this was a world leader with the system lasting until 2012. Later implementations were not so smooth. The original intention to equip the Jubilee Line Extension prior to the Millennium went horribly wrong and it was to the credit of LU that a conventionally signalled fall back was designed and installed in record time. More recently the

Jubilee Line has been fitted with the Thales Seltrac system similar to that on Docklands. This project proved to be far from an easy upgrade and much press criticism resulted from the prolonged delay and periodic weekend line closures. The system now works well and, from the lessons learned, a similar technology is being installed on the more complex Northern Line. This project is going remarkably smoothly and will be complete by mid 2014 giving a 20% increase in capacity. Disruption to the public has been minimal, most people not even realising the work was progressing.

In parallel, the Victoria line has had its original ATO equipment replaced by the then Invensys Distance-to-Go radio system. This was uncharted waters as it was an upgrade from one CBTC system to another. Hugh Bridge, who works for LU on its Automatic Train Control programme, described the solution which was based around overlaying the new infrastructure upon the old, so allowing new and old trains to run together on the line. The conversion is heralded a great success  and a significant increase in capacity – 33 trains per hour – has resulted. Current reliability levels are 4,000 hours for train equipment failure equating to three per week.original [online]

More recently, however, the contract to equip the Sub Surface Routes (Metropolitan, Circle, H&C, District) with CBTC using the Bombardier CityFlo system has had to be abandoned. The reasons for this are unclear but sufficient to say the complexities of the layouts with many flat junctions and joint running with other lines, will stretch the technology of any system that is eventually chosen.

As to the future, George Clark, the engineering director at LU, gave the current view on CBTC system capability to fit in with future London requirements. Ridership is expected to increase by 26% between now and 2024. CBTC introduction will impact on track, train, power, ventilation, signalling, EMC, tunnel cooling, platform management, telecoms, information distribution, ticketing and internet linkage.

Put succinctly, the logical progression of a CBTC is Operating Concept » Functional Requirements » Systems Architecture » Physical Structure. Following from this comes:

  • Level of Automation
  • Change to Operating Philosophy and Rules
  • Migration Strategy (duplicate infrastructure or train equipment?)
  • Simulation and Provision of Test Track
  • Integration of Different Suppliers Equipment
  • Reliability Growth by both Technology and People.

Once the system is decided upon, there come the key decisions relating to standardisation, cost benchmarking, interoperability, interchangeability, maintainability, information from diagnostics
and finally obsolescence. The information opportunities from CBTC are enormous since there is a mass of inherent data. Using this effectively should enable more innovation to
be achieved plus obtaining better security of future infrastructure. The Piccadilly, Bakerloo, Central and Waterloo & City lines will all need CBTC technology within the next few years, so the challenge will be to deploy the best system design without encountering major engineering problems.

The Crossrail Challenges

Choosing the right signalling system for Crossrail is challenging since this railway has to interconnect with existing lines east and west of London, each of which will have its own type of signalling. Equipping the central core section has caused some serious heart searching; should it have a proprietary CBTC system or try to adapt from what will eventually exist on the outer routes?

Duncan Cross from the Crossrail team explained that, once the infrastructure is completed and the trains built, to then not having a reliable control system would be disastrous. Thus the decision is to provide a proven CBTC technology for the central section. This will ensure a 24 tph capability with 30 tph as a future prospect, plus a reliable interface to platform screen doors (PSDs). Two complications arise from this however:

Interfaces and changeovers will need to happen when the trains transit to and from the existing lines.

The trains must be equipped with all the signalling systems of the routes concerned. This will include: CBTC, TPWS, AWS, ETCS Level 2 and possibly the extant GW ATP system put in as a trial back in BR days. In the fullness of time, some of these can be removed once the main line sections are equipped solely with ETCS. Initially, however, the rolling stock will have to host a bizarre collection of signalling kit.

The alternative would be to adopt the Thameslink solution for the central core by using ETCS with an ATO overlay. The fact that this does not yet exist as a proven combination makes people nervous when so much is at stake. Thus the die is cast and at least functions such as the driverless reversal of trains at Westbourne Park will be a formality.

Canadian experience

Many countries have deployed CBTC systems. One of the first was Canada with the Vancouver SkyTrain. Since the opening of the 1986 Expo Line, many lessons have been learned. Ian Graham from British Columbia (BC) Rapid Transit described the Seltrac S40 technology with full dependence on the primary system and no axle counter train detection back up.

Being a ‘greenfield’ railway with no regional line interoperability made implementation easier but whilst trains were fully automated, removing a ‘driver’ was thought to be a step too far in terms of public confidence. Later line extensions have moved towards UTO but staffing levels are still considerable at stations since PSDs have not so far been provided. UTO offers many advantages as it minimises human error, eliminates rest time periods at end stations and offers an increased service frequency with less trains.

A system must be in place to handle train failures? Roving attendants are deployed who can get to trains quickly but provision of on-train intercom, alarm buttons and CCTV is part of the safety scenario. The current throughput of 108 seconds between trains (33 tph) is capable of being decreased to 80 seconds.

SkyTrain adopted linear induction motors for trains on the first lines but a later line has conventional AC motors. In comparison, the former offers better reliability. Understanding how well the system is performing is vital and Chris Moss, responsible for the systems engineering services, explained how the technology has progressed from the transmitting of simple fault codes that were printed out on paper, to trains that have continuous data logging on to a memory stick that then acts as a ‘black box’ recorder. An instrumented test train is timetabled to traverse all lines and continually check the health of all systems, including the linear induction propulsion.

French progress

From France, Dr Pierre Messulam, the director for innovation and research at SNCF, gave a pragmatic account of French ETCS progress, now running some eight years late. Testing software between different suppliers / countries and the braking characteristics of older rolling stock have been major problems, as has the high cost of retrofitting trains with ETCS equipment that already have TVM or KVB – these being train protection systems developed by SNCF.

Bug fixing has led to successive versions of the software. More recently, interference from public GSM networks into GSM-R has meant reliability problems on the radio link, which is a serious concern. Authorisation processes are slow and complex with national authorities having different requirements and procedures.

One positive outcome is that drivers are enthusiastic about ETCS, but degraded mode working needs a lot of attention and close co- operation with signallers. Ideally a simulator is the best way of training staff on how to handle emergencies.

Introducing CBTC is seen as essential to run more trains on the existing infrastructure since civil engineering enhancements are just too expensive, so said Said El Fassi, the technical director in SNCF responsible for system modelling. Optimising the interface design with existing infrastructure is vital, especially where more than one train service operates on the same line.

Station dwell times are crucial to performance and human factor studies are important in understanding this. Modelling can save enormous amounts of time in the future and enable a better understanding of both risk and interfaces for trackside and train interworking, operating rules, environmental considerations and maintenance policies.

A new innovation in Paris is project Nexteo, a joint RFF / RATP exercise to produce a control and communication system based on CBTC principles but capable of operating on main lines where there is high density traffic. This is being designed for a new mass transit line being built but will need to integrate with ETCS as well. Something similar to the Crossrail situation comes to mind.

Safety assessment and human factors

A big factor in introducing new CBTC systems is obtaining safety approval. Paul Cheeseman from Technical Programme Delivery Systems explained the processes. The need to independently assess systems by competent people not associated with the project is insisted upon and must focus on design, development and safety measures.

It should be risk rather than compliance based, as the latter does not necessarily mean being fit for purpose. Caution must be used in using standards to mitigate risk. Two elements prevail:

The Specific Application Safety Case (SASC)

Cross-acceptance from similar systems in use elsewhere can be relevant to the GASC and need to tease out the differences from what has been approved before. Getting a GASC is tantamount to having a ‘go anywhere’ ticket.

(4)CBTC [online]Whilst many CBTC applications will aim at DTO or UTO operation, some systems, particularly where main line running is required, will retain a driver. Designing the DMI (Driver Machine Interface) is a science in itself and the gap between technology and adoption needs to be understood. Elaine Thompson from Mott MacDonald explained some of the factors.

Full integration means everything on a single screen including controls and speedometer.

The likelihood of confusion where different types of Train Protection System are required is considerable. The choice between touch screen, soft keys or separate keyboard may be influenced by local preferences. Options are being evaluated on a Class 43 HST, with the results intended as important for when the cab design of Crossrail trains is finalised.

More than just signalling

In summing up, Alan Rumsey from Delcan in Canada pronounced that installing CBTC is much more than a resignalling project, it can be considered as a total line upgrade. It is essential to focus on the real ‘needs’ (capacity, trip times, flexibility, enhanced safety, automation, lower maintenance cost.) while challenging the ‘wants’ (historic practices, need for fall back system).

A migration plan to minimise service impact during implementation is important. Operators should start with what they want to end up with and work backwards, they shouldn’t work out the first stage first.

The train is key and integrated factory testing followed by trials on a test track is the best solution. A CBTC system may be regarded as a distributed computer network so it is essential to ensure there is a stable transmission network and reliable computer hardware.

At the end of a fascinating day, Alan and his fellow speakers had done much to dispel many preconceptions as to what CBTC really entails. It really has a part to play, in fact in many cases it is essential, in keeping high-density metro rains running.

Issue 115 – May 2014

Space – The Final Frontier

Size really is everything nowadays when it comes to bulk freight movement. For evidence, look no further than the Maersk Triple E class, the latest generation of energy-efficient container ships. Carrying 18,270 20-foot boxes, these 400-metre monsters motor along optimally at 19 knots, consuming a comparatively frugal 21,200 gallons of diesel daily. Yet even these vessels have limitations despite their hefty $185 million price tag: with a draft of 14.5 metres, they are too deep to navigate the Panama Canal. Writes Graeme Bickerdike

On Britain’s railway, delivering similar economies of scale for container traffic has been consistently hampered by the less-than-generous approach taken, for perfectly legitimate practical reasons, by the Victorian engineers who gifted us our network long before the SS Ancon became the first ship to officially take the short cut from Atlantic to Pacific. Our inherited structure gauge is a function of the requirements prevailing at the time of construction, so recent years have seen a number of schemes to steal 20mm here and 50mm there, adapting the infrastructure with care and precision or, when that has failed, by means of a wrecking ball. This has allowed today’s containers to boldly go where no container had gone before. Please excuse the clumsy stumble from steamship to spaceship there.

The latest corridor to benefit heads cross country from Yorkshire to the West Midlands. The Doncaster to Water Orton W12 Gauge Clearance Enhancement project – or D2WO to save time – has been funded by the Strategic Freight Network and delivered by Network Rail’s IP East Midlands team through the multi asset framework agreement (MAFA) awarded to Carillion Rail in summer 2011. Since then, a challenging programme of 50-plus interventions was delivered through the highly collaborative approach adopted by the two parties and their key partners. Costing £25 million, the 102-mile route was cleared for W12 on time, from the end of March 2014.

It’s worth making the point that, in terms of meeting the contractual end-date, gauge clearance is an all or nothing venture: if an external force had thrust a spanner into any one of those interventions, not a single W12 wagon could have been accommodated. Success then is testament to the team’s tenacity in the face of occasional adversity. No, I can’t be more specific. And it was all done with little disruption to the network. Despite significant changes and increased scope, more than 95% of the work was delivered within existing disruptive and Rules of the Route possessions. As things should be, of course.

Too close for comfort

Proving one of D2WO’s more problematic structures was Conisbrough Tunnel, driven through a spur of land that falls southwards to the adjacent River Don. Part of the busy 75mph railway connecting Doncaster and Sheffield, the 235-yard bore comprises masonry sidewalls with a brick arch and invert, the eastern end having been constructed by cut-and-cover.

Opened in 1848, the uneven load exerted on the lining has brought distortion with it over the years, resulting in a number of remedial works. One of these saw two sections of secondary lining inserted – possibly during the 1870s – involving circumferential riveted wrought iron ribs at 8-foot centres and dished, infill brickwork. At 7.5 metres, the shorter section was thought to coincide with a geological fault near the tunnel’s midpoint; the other, 46 metres long, was further towards Sheffield. Their effect was to reduce clearances, prompting the imposition of a 50mph permanent speed restriction (PSR).Cutting [online]

In 2001, to provide some track alignment flexibility and improve clearances, the secondary lining was taken out above ballast level and replaced with an array of rock anchors, between 8 and 12 metres in length, and steel mesh. The removal revealed that an 18 metre section of original lining had been pushed upwards at the crown by 750mm, the chosen solution entailing its reconstruction with heavy-duty lattice girders and fibre-reinforced sprayed concrete. Substantial voids above the brickwork were also grouted.

Fast-forward ten years and a proposal emerges to introduce W12-gauge wagons over the route. Initial assessment work found that threading such traffic through the tunnel was feasible without substantive civils work, subject to a track lower. The involvement of Carillion Rail, the principal contractor, came as the GRIP Stage 4 (single option development) process was concluding and the firm was asked to complete an ‘early contractor involvement’ review to assist Network Rail in identifying any delivery risks and determine a target cost. Contract award came in March 2012.

Jacobs was brought in to undertake the design, development of which included a reappraisal of designs which had previously been completed. This investigation was enhanced by a walk-through and survey of the tunnel followed by an evaluation of the findings with the track and civils construction teams. This early incursion revealed that where the secondary invert was still in place, short-ended sleepers had been used which were sitting in notches cut into the brickwork. The implications of this were considerable. As things stood, in order to provide normal upper sector clearance of at least 100mm and a minimum ballast depth below the sleepers of 200mm, there was insufficient space to meet standard design tolerances. This completely changed the complexion and complexity of the project, placing evermore emphasis on that alliance between client and contractor as they sought to manage the associated risks and costs.

Room for manoeuvre

With a history of ground movement impacting on the structure, the key now was to determine whether a partial removal of the invert could be progressed without compromising the tunnel’s integrity. To that end, Jacobs procured the services of Donaldson Associates – with its recent experience modifying Conisbrough Tunnel – to support the design. Involved was a review of records gathered during the company’s previous encounter with the tunnel as well as a series of detailed site investigations. These entailed lifting the track and ballast to fully expose the secondary invert before carrying out a cloud burst survey and coring to establish its thickness and condition. Based on this work, it was concluded that the ribs and brickwork could be safely removed providing at least 300mm of lining remained and the interface between sidewalls and invert was strengthened to relieve the stresses there.

Lead [online]
Photo: Rachel Williams.
Also contributing from an early stage was DGauge, a specialist consultancy offering access to a third-generation W12 gauge providing tighter tolerances for gauge clearance parameters, typically buying designers tens of critical millimetres. Achieving this demands refined data interpretation methodology and deeper analysis of the output, as well as a risk-based approach that helps to overcome some of the conservatism associated with ‘absolute gauging’. Authority to use the tools as an alternative to industry-standard ClearRoute has to be sought from Network Rail for specific problem structures – of which Conisbrough Tunnel was certainly one – thus minimising both the track lowering and civils work needed to achieve W12 clearances.All this analysis came together to confirm that removal of just the secondary invert would provide sufficient space. With this knowledge, Jacobs was able to create a new series of track alignment iterations to identify the optimum design. Amongst the final requirements were shallow-depth, short-ended EG47 sleepers and cutting back bolt threads on several steel rock anchors which infringed on structure gauge. Fortunately the tunnel is generally dry, so passive drainage was proposed using the natural fall of the primary invert (1:559 towards Sheffield), there being no room to accommodate compliant pipework above it. Improvements have, however, been made at the lower end of the tunnel to collect any water and carry it away to the existing p-way drain.It’s worth stating that consideration was given to a high-fixity solution (slab track) but this was quickly ruled out due to the higher costs and disruption it would have brought.

The tunnel forms part of a key route, not just for local and cross-country passenger services but also overnight freight traffic.

At the races

It was recognised at an early stage that, due to access constraints, the longer section of secondary invert would have to be removed in two parts. To facilitate this, during preparatory works from October to Christmas 2013, its 20 ribs were uncovered along the six-foot and  the surrounding brickwork broken away, allowing them to be cut in half. At the invert-sidewall interface, the secondary invert was saw-cut  to leave a stub of 450mm, through which 20mm diameter steel dowels were inserted into the primary invert at 400mm centres to provide the required strengthening.

A monitoring system, installed by Carillion’s sister company TPS in early December, comprised 65 prisms arranged radially through 13 cross- sections. With baseline coordinates established, these were checked automatically by a wall-mounted EDM (Electronic Distance Measurement) device four times a day during the substantive works and twice daily at other times, the results then being emailed to an agreed distribution list. Allied to this was an alert strategy and response plan for different thresholds, appreciating of course that the tunnel naturally breathes just as we do. Movement tended to peak during or after the main possessions, with readings of 8-10mm – more than what was anticipated – recorded on several occasions. Subsequent reviews and inspections confirmed sighting issues to be the main culprit, a function of penetrating water and the plethora of furniture on the sidewalls and arch. Some prisms also succumbed to misplaced boots from time to time.

TampingRelaidTrack [online]

Fulfilment of the core works took place over seven 27-hour possessions through January and February 2014. Given the space restrictions imposed by the tunnel, choreographing which train or machine went where and in what order obviously proved critical, with a ‘racecard’ produced on each occasion detailing all the movements and associated logistics. “It’s a work-of- art in terms of the track construction chain and liaison with the civils team,” asserted Andy Robinson, the project’s design manager.

Highs and lows

First to be removed was the shorter 7.5 metre section of invert, RRVs lifting the track whilst two mini-diggers – one with a breaker, the other with a bucket – were used to tackle the ribs and brickwork. As previously stated, the 46 metre section was done in two halves – starting on the Down side – but here trains were needed to deal with the substantial arisings. Following the removal, the track was returned to its original line and level, but with EG47 sleepers. Work to implement the new alignment took place the following weekend. Attention then turned to the Up side with the process being repeated.

Subsequent to these invasive works, a cloud burst survey was performed to confirm that the structure gauge had been left clear, the onus being on the project team to demonstrate to Network Rail that the work had delivered its objectives.

This applied not just to the tunnel and those 50 other interventions, but to the whole 102-mile route.

Having originally been budgeted at around £400,000, the emerging cost of £900,000 might raise the eyebrows of anyone just crunching numbers. Back in 2012 this looked like a basic track lower; in reality, getting to the realignment stage has demanded investigations, design, civils work and monitoring that no-one had anticipated. “If we hadn’t been able to clear the tunnel in time, it would have put everything else we’d done to waste,” Alan Sheffield, Carillion Rail’s senior project manager, reflected. “And for a long time it’s fair to say that there was some uncertainty. So the headline here is that delivering it really has been a huge team achievement. There’s a great degree of satisfaction getting it signed off as clear.” And removal of the 50mph PSR – the works’ other key objective – is currently being progressed.

Giving birth to the railways brought social and economic revolution to Britain in the 19th century but has disadvantaged us in the 21st. Others learned valuable lessons from our pioneering and now find themselves better placed in terms of infrastructure. We still have to compete though. With a few obvious exceptions, we don’t build new lines anymore – that ship has sailed – so we’re faced with the prospect of evolving what we’ve got. Doing so challenges our engineers, but history proves that’s how you drive progress.

Looking to the future

Danish atomic scientist Niels Bohr is reputed to have said: “Prediction is very difficult, especially about the future”. This observation is supported by other classic comments such as: “Who the hell wants to hear actors talk?” by H. M. Warner in 1927; “We don’t like their sound” by Decca executive Dick Rowe as he turned down the Beatles in 1962 and “There is no reason anyone would want a computer in their home.” by Ken Olson, president of Digital Equipment Corporation in 1977. Writes David Shirres

The ‘Long Term Rolling Stock Strategy for the Rail Industry’ (RSS), published in February 2014, predicts that by 2043 there will be between 18,964 and 24,756 UK rail passenger vehicles – excluding London Underground and Eurostar. This compares with the current 12,647 vehicles. So, is the RSS prediction likely to better those made by Messrs Warner, Rowe and Olson? And why is it predicting rolling stock numbers so far in the future? The Rail Engineer was curious and decided to find out more.

The RSS is published by a Rolling Stock Strategy Steering Group (RSSSG) which comprises senior members of Network Rail, the train operating companies and the three principal rolling stock owners (ROSCOs), all of whom have jointly funded this work. It forecasts passenger rolling stock numbers over a 30 year period and is also intended to promote better value for money from the rail industry.

From micro-management to market driven

Rolling stock procurement after privatisation was a mess. The 5,988 vehicles built since 1994 make up 47% of the current fleet. However, as most of this new stock replaced withdrawn vehicles, the total number has only increased  by 11%. Yet it has to accommodate a 102% increase in passenger miles over the same period. The result is overcrowding and inability to meet demand. Furthermore the large annual variation in rolling stock orders since privatisation has, according to the Rail Industry Association, resulted in a loss of UK jobs and a 20% increase in costs.

Within the industry there was concern about micro management by the Department for Transport (DfT). The 2011 McNulty study observed there was “a level of Government involvement in railway affairs which many observers consider is now greater than it was under the nationalised British Rail”.

It was against this background that the Association of Train Operating Companies (ATOC) published its ‘Rolling Stock and value for money’ discussion paper in 2011 which concluded that a more market-led approach “within a high-level strategic context” was required. Its eight point plan also included the requirement for a high- level rolling stock strategy.

This approach was endorsed in the 2012 Government Command Paper “Reforming our Railways” which was shortly followed by the publication of the first RSS in February 2013. In the 2014 RSS, the previous rolling stock predictions are essentially unchanged. However it has more detail about the next ten years, standardisation, depot and berthing requirements. Both the 2013 and 2014 strategies are endorsed by a Government Minister. Thus it would seem that Government now recognises the need for market-driven rolling stock provision.

How many vehicles?

The RSS predicts future fleet sizes at the end of each five-year control period up to 2043 using forecast route-specific peak period passenger volumes from other studies. These include those published by Network Rail in October 2013 for London & South East, Long-Distance and Regional Urban markets up to 2043. It also considers the various options in Network Rail’s 2009 Electrification Route Utilisation Strategy (RUS). The RSS contains a timeline of key activities relating to franchises as these drive rolling stock procurement.

All these factors are incorporated in a spreadsheet that categorises the existing fleets into one of seven generic types of train as shown in table 1. This forecasts fleet sizes for low, medium and high 1405 Longterm RS Strategy Tables and Charts.psgrowth scenarios with low and high growth being ± 30% of medium growth. Forecast numbers are the total required. There is no detailed prediction for new vehicles as the RSS considers decisions such as life extensions are best left to the market. There is, however, an estimate of the number of new electric vehicles required based on the expansion of electrification, HS2 and the assumed withdrawal of most BR-procured vehicles.

  • In this way the RSS concludes that over the next 30 years:
  • The passenger fleet will grow by between 53% and 99%;
  • The proportion of electric (and bi-mode) vehicles will rise from today’s 69% to more than 90%;
  • Between 13,000 and 19,000 new electric vehicles will be required. This is equivalent to a build rate of 8 to 12 per week (compared to four per week over the last five years).

In addition, the number of new self-powered vehicles required will depend on future emissions legislation. With no change, no more than 100 new vehicles will be required. However more stringent legislation could result in up to 1,500 new self-powered vehicles being required.

The next ten years

The RSS recognises the importance of a detailed forecast for the next ten years i.e. Control Periods 5 and 6 (CP5 & CP6). During this time, current orders for Thameslink, Crossrail and IEP dominate rolling stock procurement. By 2019 it is estimated that 3,050 new electric vehicles will be delivered including 2,250 vehicles for these three major projects. This, and the electrification programme, will release current diesel and electric vehicles for much-needed cascades to provide more stock throughout the network. However this will not happen until the end of CP5.

The RSS forecasts that fewer new vehicles will be delivered in CP6. During this time the forecast is for 2,100 and 2,800 additional vehicles. This assumes that government policy will continue the currently committed rolling electrification programme beyond CP5.

As far as diesel stock is concerned, it is considered that no new vehicles will be required in the next ten years. By 2024 many HSTs will have been replaced by IEP trains and around 500 (50%) of shorter distances DMU vehicles will have been withdrawn including many of the class 14x ‘Pacer’ vehicles.

Electrification

The current rolling programme of electrification is a relatively recent development with only nine miles electrified between 1997 and 2010. In 2007 the Government Command Paper ‘Delivering a Sustainable Railway’ noted that “it would not be prudent to commit now to ‘all-or-nothing’ projects such as network-wide electrification for which the longer-term benefits are currently uncertain”. Fortunately, industry lobbying and the increasing political acceptance of the need for rail investment led to a change of heart. As a result, plans for electrification in the North West and of the Great Western route to Wales were announced in 2009. These were followed by plans to electrify the Midland main line and an ‘electric spine’ from Southampton.

Currently, 7,960 single track miles (41%) of Network Rail’s network is electrified and there is a commitment to electrify a further 1,900 track miles by 2019. Although the DfT cannot yet commit to an electrification programme beyond 2019, government policy indicates the programme will continue into CP6. The RSS has reviewed Network Rail’s 2009 Electrification RUS to rank route sections that might be electrified in CP6 and beyond for inclusion in its low, medium and high growth scenarios and concludes that, by 2043, between 4,000 and 6,900 track miles will be electrified as shown in table 2.

The RSS does not consider possible conversion from DC to AC electrification as this would not affect total vehicle numbers.

Value for Money

According to the McNulty ‘Rail Value for Money’ study, rolling stock accounts for 19% of railway operating costs. Maintenance and financing UK rolling stock is £1.9 billion per annum with traction energy costs estimated to be £0.55 billion. The RSS considers that rolling stock unit costs can be reduced through a combination of electrification, growth, standardisation and other factors.

Cost comparisons between diesel and electric stock show an average saving of £1.04 per vehicle mile (38%) as shown in table 3. In the medium growth scenario this amounts to £438 million per annum or a saving of 18% of total rolling stock costs.

The RSS notes that standardisation will achieve economies of scale in production, technical support and maintenance but might inhibit innovation. It does not quantify these benefits but does consider how standardisation can be improved without inhibiting commercial train procurement. This includes a description of the work of three key committees: Vehicle / Vehicle Systems Interface (V/V SIC); Vehicle / Track Systems Interface (V/T SIC) and Vehicle / Structures Systems Interface (V/S SIC).

Maintenance – Where and Who

The increased fleet will require additional berthing and maintenance depots. Provision of these facilities is well advanced for CP5. Beyond this, the RSS considers that further increases in berthing capacity of 10% will be required to 2024 and 50% to 2043. With a forecasted high demand for regional services, the largest increase in berthing capacity will be in the North West, on western routes and in Scotland. Although there will be a smaller increase in London and the South East, this is likely to be more difficult to achieve and will require advanced planning.

rolling-stock-graphic

The provision of skilled personnel to maintain the increased fleet is a critical issue. In its 2013 report ‘Forecasting the Skills Challenge’, the National Skills Academy for Railway Engineering (NSARE) notes that Traction and Rolling Stock (T&RS) is the industry sector facing the biggest skills shortage. This is because its workforce has significant numbers over 55, the large amount of new rolling stock on order and the forthcoming ERTMS rollout. The report forecasts that, within the next five years, T&RS maintenance will require an extra 4,500 technicians and 4,000 artisan staff – around 35% of the current workforce.

The RSS considers that short-term franchises do not provide the required incentive to invest in recruitment, training and development of engineering staff. It also highlights the need for long term investment to provide the necessary skills.

Creating the future

3,050 new electric vehicles and 1,900 miles of electrification over the next five years is good news indeed for the rail industry. However this level of investment has to deliver value for money as well as providing extra capacity.

Looking further into the future, the RSS becomes increasingly important in facilitating long-term value for money savings. This is because its production helps create a consensus between Network Rail, TOCs, ROSCOs and Government to ensure that the requirements for infrastructure enhancement and rolling stock provision are matched. In addition it highlights opportunities to get better value for money. Finally the RSS gives manufacturers and the supply chain the confidence to develop their production capacity.

Underpinning the RSS is its vehicle numbers forecast for the next 30 years. Forecasting as far ahead as 2043 might be thought to be an academic exercise. However this is part of a new industry long term planning process intended to take advantage of future strategic investment in the rail network of which Network Rail’s market studies are a further example.

Of course such long-term predictions involve uncertainties, but this is no reason for not looking to the future. Indeed, it may be that, in seeking a consensus view of the future, the RSS makes it more likely to happen.

Or, to quote Abraham Lincoln, “The best way to predict the future is to create it”.

Unstone’s slippery slope

On 14 January 2013, a routine run by Network Rail’s New Measurement Train on the Up Midland main line between Sheffield and Derby threw up an anomaly. There were signs of a very minor track fault on the cess rail resulting in a slight twist in the track. The fault was flagged up so that an eye could be kept on it. Writes Clare Brint

On 10 June, another run showed that the defect was slightly worse but the amount of twist was about the same. Further runs on 11 November and 9 December showed that the twist was slowly worsening and the track maintenance engineer (TME) made a comment on the fault during his periodic review of the traces, noting that it appeared ‘static’ and should be monitored.

Worsening situation

There was no other indication at that time that anything out of the ordinary was happening until, following a prolonged spell of heavy rain over the Christmas period, a ‘rough ride’ was reported on 1 January 2014. The fault was manually corrected by the permanent way team but, unfortunately, re-appeared several times over the next three weeks. Every time that the track was lifted and packed to correct the fault, there was rapid deterioration afterwards.

By 21 January, a 50 mph temporary speed restriction (TSR) was imposed. Track patrollers noted that the cutting slope appeared to have lowered, the catchpits were leaning and they suspected that the earthwork might be the underlying cause.

Meganne Paul, Network Rail’s asset engineer, visited the site on the following day and the scale of the problem became clear. Network Rail’s Infrastructure Projects (IP) team were engaged to start work the same day and Principal Contractor Construction Marine Limited (CML) was on site the next morning.

Understanding the problem

It was clear from the initial visits that an area of the hillside about 100 metres wide and 100 metres long, the bulk of which was outside of Network Rail’s land, was moving down the slope in a series of slips. The lowest slip had moved into the cess area and was pushing the cess rail up.

There were some spoil heaps of recently tipped material in the upper slope immediately below the backscar. Aerial photographs taken using Network Rail’s helicopter were very useful in helping the team to visualise and understand the slip.

It had happened before

Records retrieved from Network Rail’s National Record Group (NRG) in York revealed some very interesting history. In 1969, the old Broomhouse Tunnel, located a few hundred yards south of this site, was opened out into a cutting and the contractor who carried out that work was paid to remove the spoil. The notes stated that “after a winter’s experience it was found necessary to carry out further excavation to stabilise the cutting”, and this work was carried out by the same contractor as an extension of the original contract.

The site for the tipping of the spoil from the original contract had been restored before the additional work was authorised, so the contractor therefore found it necessary to negotiate for another site for this additional spoil. A private arrangement was made with a local landowner to place the material in an area of ground adjacent to the railway known as Thorpe Spring Wood or Spring Bank Wood.

The slope was stepped and the spoil material placed in September 1970. Three months later, a landslip occurred which resulted in a caution being put on the trains due to slight movement in the rails.

Urgent remedial works discovered that the spoil had been placed on top of two natural springs, one in the upper slope and one in the lower slope. Ground investigation and monitoring instruments installed at the time indicated that movement in the upper slope was occurring  at the interface between the fill and the natural ground and that movement at track level was caused by the weight of the additional spoil on to the natural weathered rock which had previously been softened and saturated by the lowest spring. Movement of the lower slip was therefore occurring through the natural soils. The remedial works included removal of some of the tipped material and installation of drainage designed to intercept the natural springs and dry out the lower slope.

Ongoing monitoring of the slope continued from 1970 and included measurement of groundwater levels, installation of slip indicator tubes to pick up depths of deep-seated movement, and the 140316 Unstone [online]monitoring of pegs to pick up surface movement.

Over the next few years, it was found that, although further slight movements were recorded in the hillside, the slip was no longer affecting the railway and that the previous remedial works and drainage measures appeared to be effective.

The British Rail civil engineering department continued to monitor the slope and, by 1977, movements in the hillside had become sufficiently large that further work was proposed to safeguard the railway. These included additional drainage improvements and the installation of an automatic trip wire landslip detector, both of which were put in place during 1978/79.

It appears from the available archive information that, following these works, British Rail considered the landslip was no longer affecting the railway. There are no further records of monitoring of the slip indicators or groundwater levels after 1986 and the landslip detector had became redundant by the 1990s.

Back to today

Although it was hoped that the line could be kept open with the movements being managed by the track maintenance team, the Train and Freight Operating Companies (TOCs / FOCs) were advised within the first week that they should start preparing plans for line closure. Track maintenance engineer Mark Owens and his section manager Phil Milner developed a detailed and clear plan to react to deteriorating twist levels and ensure the safety of trains. In this particular situation, and given the number  of unknowns, the plan included limits for reduction in speed and line closure which were set at more conservative values than those mandated by Network Rail Standards.

Phil Milner and his team visited site daily and, when movements increased, maintained a 24-hour presence on site, monitoring for track movement and lifting and packing as required. In addition, CML were on site surveying the hillside daily. As an extra precaution, a system of remote monitoring was installed on the sleepers to give 24-hour twist values and text alerts if these deteriorated. All of this monitoring information was reviewed, as it was received, by the geotechnical, track and project teams so that correct decisions could be taken regarding safe line speed.

To make sure that the operators could fully understand the situation and the potential impact it might have on their customers, Clare Brint, Network Rail’s senior geotechnical asset engineer, provided a daily email update and attended frequent teleconferences to keep everyone informed. These updates included information on the amount of movement in the hillside and at track level, and predicted the deterioration rate so that an estimate could be made on how much longer the line could be kept open.

As understanding of the landslip, its history, behaviour and effect on the track increased, CML and their design engineers developed a plan to address the lowest part of the hillside first, in order to halt further movements at track level. This would be followed by remediation work to the whole hillside.

Closure and reopening

Following several more days of heavy rainfall, there was significant further movement at track level. The decision was taken to give the TOCs and FOCs 36 hours notice that the Up line would be closed
on the morning of Tuesday 18 February 2014. At that stage, the programme for the works to allow the line to be re-opened was six weeks from the date of closure, which would mean it would not reopen until the end of March.

This was due to the anticipated length of time to excavate the shear trench in short lengths to protect the stability of the hillside and constraints both with on-site materials storage and vehicle movements into and out of the site.

The lowest slip was remediated by the installation of a ‘shear key’ – a 100 metre long stone-filled excavation, five metres wide and five to six metres deep, which went below the level of the slip.

This work took just three weeks and successfully prevented further movements at track level.

It had been anticipated that a full track renewal would be required due to the clay material having been pushed up, contaminating the ballast. This would have required plant, equipment and staff to be diverted from planned track renewals as well as up to two days of full line blockade for both lines. However, in response to a request to speed up the process, a number of various other options were explored. It was decided to use the High Output Ballast Cleaner (HOBC) to excavate and replace the contaminated ballast as an interim measure.

Following confirmation that the shear key was effective and the slip had stopped affecting the track, the HOBC was used on the night of Friday 7 March, allowing the line to be re-opened on Saturday 8 March 2014 at 50 mph and returned to line speed the following week.

The hillside continues to move, and work is still underway to remove up to 100,000 tonnes of soil and ensure that these slips do not affect the railway again. It is estimated that this will take a further three months, after which a full track renewal is being planned for 2015/16.

That should put an end to the story of Unstone’s slippery slope, a tale that started forty-five years ago.

Canal Tunnels – Exercising foresight

In 2004, Great Britain won nine gold medals at the Athens Olympics. In 2005, Tony Blair won a third term as Prime Minister and then there was the World Cup in Germany in 2006 – but we won’t dwell on that.

Whilst the world was focussed on these and many other events the Channel Tunnel Rail Link (CTRL), as part of the Thameslink Programme, was quietly digging underground, constructing two bored tunnels between the East Coast main line (ECML) at Belle Isle junction, just north of Kings Cross, and the St Pancras low level station at Canal junction. As the two tunnels pass about 15 metres under the Regents Canal, they are known as the Canal Tunnels.

Each tunnel was constructed with a six metre diameter bore and fitted with a pre-cast concrete lining, and they are both more than 660 metres in length. At the King’s Cross end there is a 100 metre cut-and-cover concrete box which leads up to an open area which, in total, forms a 1km length of new twin track railway.

Thameslink progressing

Since they were built, the tunnels have remained dormant. Elsewhere, the Thameslink project has been progressing steadily – reconstructing Blackfriars Station, building a new viaduct through Borough Market and developing the London Bridge Station and railway layout are just a few of the many schemes that make up this incredibly complex £6 billion project.

However, one of the key benefits that will be realised when the Thameslink project is completed will be the ability to run 24 trains per hour between Blackfriars to St Pancras Low Level which is known as the ‘core area’. This target will include 16 trains coming from the Midland main line route and eight trains from the East Coast main line, hence the need for the Canal Tunnels now to be fitted out and integrated into the operational railway.

In addition, the new Thames link Class 700 rolling stock is due to begin arriving in 2015, and is expected to be used on both the existing Thameslink and Great Northern routes. One of the Thameslink depots will be at Hornsey on the ECML. Therefore, the tunnels will be essential to enable the new trains to utilise the link for stock movements.

canaltunnels 090 [online]

Contract awarded

Consequently, in August 2012, an announcement was made by Network Rail naming Carillion as the principal contractor for fitting out the tunnels and connecting them into the main lines. Balfour Beatty Rail would be responsible for the 25kV overhead line electrification (OLE) installation work and Carillion would install the slab track, associated emergency walkways, signalling and telecomsequipment, fire services and pumps and other associated safety equipment throughout the tunnels as well as being the overall site management.

Kevin Sullivan, Network Rail’s project manager responsible for this work, recently showed The Rail Engineer around the site. He explained that the work was progressing very well and that the construction of the slab track work in both the tunnels was now complete. Also, the installation of OLE equipment by Balfour Beatty Rail, using its innovative reduced-depth overhead conductor beam electrification system, was going to plan. Kevin explained that they were now concentrating on connecting the new emerging Up and Down Canal Tunnel lines into the existing mainline routes.

Collaborative working

Carillion appointed ARUP for all the design work. The tunnels are only six metres in diameter, which is a challenging space to fit everything in and the aim was to maintain W6A gauge. In addition, the tunnels will connect two different railway systems together so there is a need to design out any potential interference. For example, it would not go down well if, upon connection, there were track circuit failures on the ECML. As Kevin outlined, there has to be effective collaborative working between all parties and to ensure that this happened. “We have instigated weekly design integration meetings between all disciplines and Network Rail, a process that has proved to be very successful and invaluable,” he explained.

To ensure compliance with noise and vibration commitments, the track was designed using the Sonneville Low Vibration Track (LVT) system supplied by the Swiss manufacturer Vigier. This system is a duo block, slab track system with a rubber boot and concrete block pad. It has been tried and tested on other systems throughout the world but it is the first time that it has been used by Network Rail. The rubber booted blocks are cast into concrete exposing the concrete block pad which is designed to hold in place the rail and the pandrol E clip housings and insulations.

Challenging tolerances

The final positioning of the rails is very precise with only 1 to 2mm tolerance for gauge, rail incline and cant. As Kevin pointed out, this could only be achieved on a dedicated engineering site, as opposed to a track possession. The design life chosen for the concrete surrounding the rubber boots is 50 years and the design life for the sub base concrete is 125 years.

The signalling and telecommunications design is integrated with the Thameslink programme’s High Capacity Infrastructure (HCI), which ensures that the signalling system will deliver the targeted 24 trains per hour capacity in the core area.

A GSM-R radio system is being installed throughout the network to replace the Cab Secure Radio system currently in use. To ensure this will work well inside the tunnels, a ‘radiating cable’ or ‘leaky feeder’ is being installed throughout.

Walking through the tunnels, it is obvious that there is a steep gradient dipping down 1 in 34 toward the centre of the tunnel bores. This encourages any rain or seepage water to gather at this low point. Also, there is a 150mm fire main that runs through both tunnels with regularly spaced hydrants that can be accessed from the constructed walkway. So, if there was a fire and the fire main was utilised, the tunnels could be subject to flooding. Therefore, to cope with such a potential high volume of water, a 60 metre long sump has been installed incorporating fixed pumps that will pump water up the gradient to another intermediate sump which, in turn, has the capacity to pump water up into the existing East Coast main line drainage system.

The fixed walkway provides a continuous platform to enable day-to-day maintenance to take place and to provide a passageway in case of emergencies. A lighting system has been installed throughout the tunnels with lights spaced at every four metres above the walkway.

On the opposite side of the tunnel, there are two GRP troughing routes dedicated to signalling, telecoms and other mechanical and electrical equipment ensuring that everything looks neat and tidy and well ordered.

Continuous working

Work continues around the clock in two 12-hour shifts. Carillion works the day shift installing the slab track and other equipment, then the site changes over to Balfour Beatty Rail activities, using rail mounted access platforms to install the Conductor Beam OLE equipment. Kevin said that this system works very well and that each contractor has tried hard to ensure that its activity does not impede other work that has to take place.

So, the fitting out work in the tunnels appears to be progressing very well and targets are being met. The next challenges for the team were the connection work at each end of the tunnel into the main canaltunnels 086 [online]lines. The junction at Belle Isle is conventional ballasted track whilst, at the St Pancras Low Level station end, the junction is on LVT concrete slab track.

Kevin described the project as being unique in that there is a fascinating and challenging engineering project in the tunnels, a site that they have control of 24 hours a day. However, at the two end connection points of the site, there is a railway so it is necessary to work in possessions, being aware of hazards such as adjacent line working where traffic is running. This introduces a whole set of different risks and challenges.

At Belle Isle Junction, existing structures have had to be demolished and new ones installed. The existing sheet piled wall of the ECML railway has to be removed to make way for the new connection. The junction is situated in a fairly confined location between Copenhagen Tunnel and the Gaswork Tunnels just outside Kings Cross station.

In preparation for the connection of the new junction, a set of switches has had to be moved six metres north to accommodate realignment of the North London Incline. In addition, 140 metres of plain line has had to be renewed and a crossover was repositioned 30 metres north of its original position during an Easter 2014 blockade.

Connecting into the main lines

So, the site is nearly ready to receive the new double junction which will be installed using a Kirov crane to lift track panels that are being constructed alongside the running railway. After the new junction is in place, it will be connected to plain line track that will be laid on a transitional formation of ballast. This will then lead onto a formation of glued ballast, then onto slab track, before running into the Canal tunnels. The completed work will then be ready for commissioning with control located in the Kings Cross Panel.

The Canal Junction end of the site is now all LVT slab track, installed some time ago. It is where the Moorgate lines emerge from the lower station at St Pancras, switches and crossings had to be relocated and aligned and replaced by plain line. Once this work is complete, the junction can be commissioned onto the new Three Bridges Rail Operating Centre (TB ROC) which will then incorporate the whole of the new railway. The target date for the completion of this work is early 2015.

The commissioning of the tunnels is yet another step in this most fascinating project known as Thameslink, and one has to admire the foresight exercised in 2004 which ensured that the two tunnels would be ready and in place. The fitting out work will be completed this year, the Hornsey Depot will be completed in 2015 and the Siemens Thameslink Class 700 trains will begin delivery and then in 2018 services will run through the Thameslink core. Meanwhile, there is plenty to do, both within well-defined engineering sites and alongside the operational railway, which will provide more unique opportunities for the engineering teams involved.

Ipswich chord and freight yard

On 24 March, GBRf locomotive 66733 hauled the 11:33 from Felixstowe North Terminal to Doncaster Railport, becoming the very first revenue earning freight train along the newly commissioned Ipswich Chord. Writes David Bickell

Following the running of this ‘test train’, the Chord opened to commercial traffic on time and on budget from 31 March. In railway operating terms, the Chord is now known officially as the ‘Bacon Factory Curve’, named after the Harris Bacon Factory which previously occupied part of the triangle created by the new line.

Changes over time

A brief step back in time reveals that the development of Felixstowe as a port came about in the nineteenth century thanks to the vision of one man – the wealthy Victorian George Tomline. He believed that Felixstowe could be developed to rival the port of Harwich on the opposite bank of the Orwell and Stour estuary, and drafted infrastructure plans for the railway and docks. Parliamentary approval was given in 1875 for the building of the Felixstowe to Ipswich line, which transformed Felixstowe from a small seaside village into what would become the UK’s largest container port and the sixth largest in Europe.

However, over the years, the rail infrastructure has struggled to keep pace with the rapid expansion of the container port. This is being addressed and the new Ipswich Chord forms part of the Felixstowe to Nuneaton (F-N) capacity upgrade project.

Felixstowe’s train services are now dominated by freight traffic to and from the port. Although Felixstowe remains a popular seaside town, the days of hundreds of trippers alighting at the station are long gone. The passenger service between Ipswich and Felixstowe is a shadow of its former self. The once extensive Town station, with four long terminal platforms, has been cut back to just one shorter platform that is sufficient to serve the hourly Class 153 shuttle. Nevertheless, these trains have to share the single line with the container trains serving the three Felixstowe freight terminals.

Main line snarl-up at Ipswich

Container trains from Felixstowe generally proceed via East Suffolk Junction into the Yard at Ipswich for a crew and/or traction change before continuing via the Great Eastern main line (GEML) to Stratford and thence via the North London line to join the West Coast main line. Some trains reverse in Ipswich Yard and initially head north before veering west at Haughley Junction on their way cross country towards Nuneaton.

The GEML route is already very busy with a mixture of InterCity, semi-fast and stopping outer suburban trains. The container trains have to be accommodated with these passenger services on what is basically a twin-track railway from Liverpool Street to Ipswich, with limited opportunities for fast trains to overtake at Chelmsford, Witham and Colchester.ap02-Ipswich-Chord-Visit2 [online]

Stratford is a challenging pinch-point for signallers. Whilst there is a second pair of tracks (‘Electric Lines’) between Liverpool Street and Shenfield, these are due to be handed over to Crossrail services in 2015. It seems unlikely that operator TfL will be see the offering of paths for freight trains as being compatible with the running of a reliable metro-style service.

Furthermore, there is a local ‘Norwich in Ninety’ campaign underway to reduce InterCity journey times between Norwich/Ipswich/London. The best time today of 100 minutes is achievable with only one train in each direction with specially crafted paths. Given the mixed-traffic nature of the twin-track main line and the knife-edge performance of the intensive morning and evening peaks, achieving such a reduction in journey time is likely to be challenging. However, this is where the Ipswich Chord can help increase paths for faster and/or more passenger trains by reducing container traffic routed via Stratford.

October 2012 – March 2014

Devised as part of the F-N capacity upgrade, the Ipswich Chord is a brand new double track section of railway 1.2 km long with double junctions at each end. It cost £59 million, co- financed with a contribution of £10.7 million from the European Trans-European Network (TEN-T).

Prior to the opening of the Chord there were 28 freight trains per day in each direction, 18 via London, 10 via Peterborough. When the Chord is at full stretch in 2030, after other infrastructure improvements are complete, it is anticipated that there will be 56 paths each way, though some may still be routed via Stratford.

The new chord line is the first Network Rail line to be authorised under ‘The Railways (Interoperability) Regulations 2011’. Certification will be achieved by the Network Certification Body, an independent subsidiary of Network Rail. NCB is accredited to act as a Notified and Designated Body (NOBO) to certify project compliance. Technical Specifications for Interoperability (TSIs) are drafted by the European Railway Agency and mapped to Railway Group Standards in respect of UK railway standards.

At the time of application, Network Rail envisaged that interoperability as a freight line was appropriate. Subsequently it has been realised that passenger services may use the chord. Indeed, several charter rail tour operators are already advertising tours that traverse the new chord line for the benefit of ‘track bashers’. Accordingly, now the line is open, application will be made to reclassify the line as ‘mixed traffic’.

Taking the chord

Container trains from Felixstowe docks approach the Ipswich suburbs from a north easterly direction along the East Suffolk line from Lowestoft which is joined at Westerfield. An existing bridge over the River Gipping has had to be replaced with a new wider structure known as Boss Hall Bridge. The track bed on this structure incorporates the switches of the new Boss Hall Junction.

Freight trains taking the chord then veer right onto new embankments – which even include reptile basking areas. A new underbridge provides maintenance access to the land that is now enclosed by the new triangle of lines.

Continuing around the chord, after a new bridge across the River Gipping the line runs alongside the Norwich main line in a north-westerly direction for some 650 metres. This is to ensure that the length of chord is sufficient to stand a 775 metre long freight train clear of the main lines in both directions. A long retaining wall with soak away segregates the railway from various properties including a supermarket and bowling alley.

Another new bridge takes the chord across the Sproughton Road. The line then converges with the main line at the new Europa Junction where freight trains, after awaiting a suitable path, continue on their journey westwards via the cross-country route. Europa Junction is designed for 50 mph and provides for the shortest possible time for a train entering the Up curve to clear the junction and avoid delaying a following passenger train. The curve itself is limited to 30 mph.

The Works

The principal contractor for the scheme was the Spencer Group working jointly with Network Rail. Spencer Rail constructed the four new bridges on the Chord. Jacobs Engineering UK Ltd delivered consultancy services including preparation of documentation and environmental considerations. CSL provided project management and delivery consultancy for the SMEs involved and structures work.

The existing Underbridge 404 across the River Gipping on the East Suffolk line was in poor condition and, as the new crossover would occupy much of the bridge, a wider structure was required. Network Rail’s standard half-through Type E design with steel deck was chosen for the new span, which is 23.9 metres wide. The new abutments and wing-walls are clad with bricks chosen to replicate the blue engineering bricks of the original, now demolished, abutments piers.

Other works included a further three new bridges, a long retaining wall, and tunnel construction to re-route a sewer. Design of the new River Gipping bridge had to make provision to allow the Environment Agency to gain access to the sluice gate and the embankment and for the future provision of a cycle path. Sustrans had requested that the new River Gipping bridge should provide the necessary engineering to allow the cycle track to be extended and to offer a continuous path and DDA compliant ramp for the benefit of pedestrians. National Cycle Network 51 is constrained by the existing bridge/sluice structure and this should not be made worse by the scheme.

Electrification ready

Although there is an aspiration to electrify the cross-country route from Felixstowe to Nuneaton, at present OLE work is limited to the modification of existing wiring where the chord intersects the GEML at Europa Junction. The building of the new embankment parallel to the main line would have destabilised the OLE stanchions. Accordingly, new catenary has been installed along the embankment and across Europa Junction. The junction tracks have also been wired plus a 150 metre section of the Up Curve. This is part of future proofing and will obviate the need for complex alterations to the catenary here if electrification of the chord proceeds at some point in the future.

50221184dc298c6a5c7b2eb9a377d2ee-xlarge[1] [online]The short wiring on the chord covers the scenario of an Up electric train being mis-routed onto the curve, providing a margin for a driver to react to a signal displaying the route indication for the Up curve and being able to bring the train to a stand before the pantograph runs out of catenary causing damage and the train becoming powerless. The chord is ‘electrification ready’ in that the proposed positions and clearances of OLE masts has been taken into consideration with the design of the various retaining walls and structures. Pod-Trak Ltd has provided the AWAC MkIIIb catenary. This utilises an aluminium conductor with two aluminium-coated steel cores for strength. AWAC uses a different suspension arrangement compared with earlier steel types. At the pulley wheels, stainless steel bridles are deployed as the aluminium would wear rapidly if it ran over a pulley.

Modular track

Ian Clark, Alma Rail’s project track engineer, explained that the track sections were built at Doncaster, to the design radius of 203m and pre-drilled at Doncaster by VAE, consisting of twenty-seven 60-foot panels on the Up and Down lines with breather switches at each end. A McCulloch Rail HD panel-moving machine was deployed for this work. The chord has been designed at the maximum radius possible and a lubricating system will be used to mitigate any possible noise.

CEN56 ‘FV’ IBCL switches have been installed at each junction. The junctions include the first use on Network Rail of modular switch diamonds. The original plan was to install the S&C at Europa Junction during Easter 2013 but, due to snow, this work was postponed. Prudent contingency in the planning of the project allowed for this work to be rescheduled. During the Christmas 2013 blockade, due to the phasing of the signalling commissioning, three dummy plain line panels were installed at Boss Hall Junction with the real switches following a week later.

Signalling

Previously, Ipswich station area was provided with four-aspect signalling, with three-aspect signalling on the approaches to East Suffolk Junction from both the Norwich and Lowestoft lines. To allow for adequate junction signalling onto the new chord from both Norwich and Lowestoft lines, four-aspect junction signals have been provided for both new junctions with the provision of flashing aspects on the approach to the junction signal at each divergence. Signals on the curve are three-aspect.

Visible on the chord are the new lightweight LED signals, clamp lock points, and apparatus or ‘location’ cases. However, out of the public gaze, in relay rooms and the signal box, the project has required significant and complex signal engineering works.

Ipswich is on panel 5 at Colchester Signal Box. It is a combined near vertical control and indication NX Type and was manufactured by Henry Williams Ltd and commissioned in 1983. The panel consists of small individual battleship- grey ‘Domino’ type tiles which slot into a metal lattice in the rear of the panel. The company has returned 30 years later to incorporate the curve into the track layout diagram.

The section of the panel that the new chord line affects is at the bottom right hand side. It is already quite congested as the lines towards Norwich and Lowestoft are skewed to allow alignment with Panel 6. As the new layout incorporates new signal sections on both Up Main and Up Lowestoft lines as well as the Chord lines, there are new Train Describer (TD) windows, track occupied/route indications and buttons to be provided.

The main commissioning was in March 2014 but enabling works took place late last year during which the existing panel tiles were relocated to free up sufficient space for the Ipswich Chord lines.

Henry Williams Ltd also provided signalling Class I power supply location cases.

Signal interlockings

The Ipswich interlocking is situated in a room on the station. Unfortunately, the distance to the new junctions is just outside the maximum 1.25 miles distance for lineside multicore 50V DC signalling safety circuits. Beyond this distance, repeater relays would be required to ensure that induced currents from the 25KV OLE do not create a potentially dangerous false feed. There was insufficient space to locate the interlocking at Ipswich station for the new junctions, and this would anyway require long runs of multicore cables.

The novel solution adopted has been to build a new relay interlocking in a relocatable building near Hadleigh Road bridge. Incidentally, for a small scheme such as this, a new relay interlocking is a more cost effective solution than a computer based version. This interlocking is linked by a new Time Division Multiplex (TDM) data transmission system to Ipswich relay room. The controls and indications data is then transferred via the existing TDM connecting the existing Ipswich relay room with Colchester. GE Transportation Systems (GETS) was the contractor for the TDM and TD systems.

The existing interlocking at Ipswich is a GEC geographical relay system. Some minor modifications have been necessary for the chord, but this interlocking will be extended during this summer in conjunction with the East Suffolk Junction remodelling, of which more anon.

Amaro Signalling Ltd was responsible for lineside signalling equipment, new interlocking and alterations to existing interlocking.

Aerial views of the Ipswich Chord Project

Ipswich Yard and East Suffolk Junction remodelling

This project, also funded under CP4 and part of the Spencer Rail portfolio of works, will create a new longer reception siding. Currently the yard cannot take 775 metre long trains. When resignalled in 1984, the layout of East Suffolk was rationalised from a double junction to a single lead. This prevented a freight train arriving in the yard from the docks simultaneously with a passenger train heading for Lowestoft or Felixstowe. A new line will be installed using a disused arch of the Hadleigh Road bridge, thereby restoring the facility of parallel moves at the junction. This work is due for completion in August this year.

CP5 and beyond

Further improvements on the F-N route are funded under the CP5 package including Haughley Junction doubling from single lead, Ely to Soham doubling and provision of Ely Dock Junction long freight loops. As well as increasing capacity for freight trains, Greater Anglia has aspirations to increase the current two-hourly Ipswich to Peterborough passenger service to hourly.

As described above, the all important Felixstowe branch suffers from the severe capacity constraint of the single line. At GRIP Stage 2, options currently under consideration include a new dynamic loop, passing loops and the relocation of Westerfield station. Complete redoubling is unlikely, not least due to the Spring Road viaduct which would be very costly to replace. The Network Rail project team is hopeful of match funding from the Port of Felixstowe and that capacity improvements should be completed by 2030.

Investment in this route is critical to improve the distribution of goods from Britain’s largest container port with the potential to take up to 750,000 lorries a year off the roads by 2030.

Costain: Moving into REAL rail

Costain is a well-known name. It must be so as, in the waiting area of the company’s headquarters in Maidenhead, there is a large coffee-table book entitled “Business Superbrands”. Costain’s name is in there.

Most people would associate the Costain name with major, prestigious, one-off projects such as the Thames Barrier (1982), the Channel Tunnel (1993) or the new Hong Kong airport (1996). One might also link the Costain brand with civil engineering associated with the railway environment, but it is fair to say that many would not consider Costain to be a major rail engineering company. However, they would be wrong, and that is why The Rail Engineer went to meet Gren Edwards, Costain’s director of rail, to discover the story behind this significant move into real rail engineering.

Gren joined Costain in December 2010. His objective was to grow Costain’s rail engineering business by acquiring the skills required and to use the significant talent that existed within the company’s 5,000-strong workforce.

Before joining Costain, Gren had developed a wealth of experience by creating a railway engineering company, Grant Rail, which started as a supplier to other contractors before emerging as a principal contractor for Network Rail and London Underground. When that company was acquired by the Dutch-based business VolkerWessels, he stayed on as CEO of the emerging company VolkerRail.

Shortly after joining Costain, Gren appointed Ross MacKenzie as customer director. Ross, an ex-army major, has been with Costain since 2008.

Early railway projects

At the time Gren joined Costain, it was already carrying out a number of prestigious and important railway projects. For example, the company had been working for Union Railways since 2001, cutting 18km of twin 8.15 metre diameter tunnels through the densely populated east end of London working in close proximity to other rail tunnels. Costain created a joint venture (JV) with Skanska and Bachy to win this contract’ and they succeeded to deliver the tunnels ahead of programme and within budget.

As part of the high speed project, Union Railways needed a prestige London terminus for the new Channel Tunnel service. St Pancras station was chosen but at the time it was in very poor condition. A JV was formed led by Costain and the project went on to be an award winning success and London now has a station of which it can be truly proud.

Some time ago, supermarket chain Tesco developed a plan to build a store over a cutting through Gerrards Cross in north London. A contractor was engaged to bridge the cutting by creating a tunnel over it. Unfortunately, the tunnel partially collapsed in 2005, blocking the railway line. In 2006, in collaboration with Network Rail, Tesco approached Costain to find a way to complete the tunnel and allow the store to be built. Costain redesigned the tunnel using wherever possible the materials already on site and built the new store and car park.

Little acorns!

Then in 2008, Network Rail appointed the Costain Laing O’Rourke JV to construct the enlarged station at Farringdon as part of the Thameslink and Crossrail schemes. This was a complex programme which combined traditional civil engineering with complex and often detailed trackside work, requiring possession management skills and a significant awareness and appreciation of signalling, power and other operating systems. Costain introduced a novel temporary platform system to protect the track from heavy plant movements. It was deployed quickly at the start of the possession, and easily moved at the end to restore the track to full operational order.

Work at Farringdon Station was still in progress when Gren joined Costain and he was keen to point out how pivotal this programme of work was. It enabled Costain to gain credibility as a contractor which fully understands what is involved when working alongside an operational railway. As a consequence, it also offered Costain an opportunity to move from a stop-start rail business to one that has consistent turnover with a continuous flow of work.

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Photo: shutterstock.com.
In order to enable Costain to build credibility with their clients, Network Rail, London Underground, Crossrail and Thameslink, it was agreed that they would need to develop their technical expertise. Therefore, Gren appointed a Professional Head each for Track, Electrification, Rail Civil Engineering and Signalling. Gren emphasised that, even though at present they have not yet ventured into signalling design and installation, they need to have the knowledge and the associated awareness to function effectively in an operational railway environment, hence the post. With these key personnel in place the company could start to offer a quality service to the client that was different. It would not only draw in the newly acquired railway skills but it would also enable Costain to share and transfer the significant skills, lessons learnt and experience that had been gained over the years in Costain from working in Nuclear, Water and Highways.

Emerging business strategy

Ross MacKenzie then explained the broader strategy that they adopted. Traditional railway work such as that at Farringdon, St Pancras, Gerrards Cross and, as principal contractor, at Reading and London Bridge stations is always going to be an important part of their portfolio.

However, to create consistency of work flow, the company needed to win contracts that are more closely associated with the operational railway. This it has managed to do by successfully tendering for the five-year, multi-discipline, Network Rail framework contract for buildings, civils and enhancements for the Southern Region (Kent).

Alongside this initiative, Costain has been awarded Network Rail’s north-east infrastructure and stations project, which involves remodelling a significant number of stations on the north- eastern part of the emerging Crossrail network. In addition, there are significant upgrades of track and associated electrification and signal integration. This is a diverse package of work to be completed over the next 3 years. Writes Colin Carr

Complementary skills

In parallel to this, the Costain team’s strategy also focuses on areas of work where the diverse range of skills required favoured a JV approach. This was particularly appropriate if Costain wanted to feature in Network Rail’s electrification programme and, after three years of behind the scenes discussion and negotiation, ABC Electrification emerged (Alstom / Babcock / Costain), a reputable power-house of complementary skills and experience.

To date, ABC has won contracts for the electrification of the London North West (South) route (£435 million), Edinburgh to Glasgow Improvement Programme (£75 million) and, just recently, the Welsh Valley Lines (£450 million). Alongside this significant package is the previously-awarded West Coast main line power upgrade phase 3B work worth £50 million.

To round off the strategy, the Costain team started to look at multi-disciplinary systems, focussing specifically on the fit out programme for all the Crossrail tunnels. Another joint venture has emerged, known as ATC (Alstom, TSO, and Costain). This JV has the combined skills to install track, overhead line and power supply equipment and it has been awarded three Crossrail contracts valued at £300 million.

Develop solutions

As Gren pointed out, it makes for a fascinating story which is a testament to the talent that exists within the company. He believes that one must have the ability to listen to what the client really wants and then develop solutions, often to challenging problems, to deliver what is required. Clearly, the order book shows that Costain’s various clients do think that Costain has the ability to find solutions to challenging problems and they do think that Costain is a company that fully understands the challenges which an operational railway environment can throw up. To put this into numerate terms, the turnover for rail related business within Costain in 2010 was about £30 million per annum, with significant peaks and troughs. Today, the turnover is £300 million per annum, which is sustainable, and there is a forward order book of around £1.4 billion. The figures speak for themselves, and now nobody can deny that Costain is a ‘real’ rail company.

Acoustic sensing: The future for rail monitoring?

The advent of fibre optics some 30 years ago revolutionised telecommunications transmission technology. Since then, other applications of light source emission have emerged which could have a similar impact on aspects of everyday life. Writes Clive Kessell

One such by-product is the measurement of acoustic energy, which sounds complex but, in real terms, is simply the recognition of noise and vibration near to a fibre optic cable.

This is now used in a variety of industries worldwide for event detection. It first came to the notice of the UK rail sector in 2010 when a train was derailed in Scotland after hitting a boulder that had rolled on to the line in the Pass of Brander between Glasgow and Oban. The existing detection system, comprising of a mechanical system of trip wires, had failed to detect the incident and the Network Rail Glasgow team looked around for better ways of detecting falling boulders and other objects.

A test site was established to see whether a fibre cable would pick up such a situation with promising results. An article describing the test appeared in the March 2012 edition of The Rail Engineer.

Since then the technology, which is now called distributed acoustic sensing (DAS) has moved on apace and The Rail Engineer recently visited OptaSense at its research and development facility in Winfrith, Dorset, to meet with the team headed by chief technical officer Dr David Hill and learn more.

So what is acoustic sensing?

Every time even something as small as a human footstep is taken, a small amount of energy is transmitted into the ground. If a sensing mechanism is placed near to the event, the vibration will be picked up and can be transmitted to some form of monitoring equipment where the event can be analysed for type, strength and location.

The breakthrough has been the ability to use an optical fibre as the sensing device. An injected light source sees a marginal change in refractive index at the point of disturbance, thus causing a change in the reflected signal from that point. The time for the light to travel back to the source enables the distance of the disturbance from the origin to be calculated.

Since fibre optic cables are now commonplace alongside railway tracks and roads, it may not be necessary to lay a dedicated cable but merely allocate a spare fibre in an existing cable. The positioning of the fibre relative to the likely interference source is not critical but there are optimum places where it will perform best.

For a railway line, burial about 10cm down near to the sleeper end will enable detection of even the smallest incursion on to the track while having two fibres, one each side of the track, is perfection. Unless a dedicated cable is to be laid, however, these situations will not be the norm. An existing cable laid in a concrete trough, a buried pipe, or directly in the ground, will still pick up acoustic energy from close by events.

Clearly, a passing train will give a very strong signal and any rock fall will equally give a clear indication of something happening. A track gang working with shovels to dig holes or pack ballast will be picked up, as will someone using a hacksaw to cut cables in the route. With experience, every type of occurrence creates its own recognisable pattern which can then be ‘decoded’ at the monitoring point.

System development

Having established the technical principle, turning this into a practical way of realising the potential is a project in itself. OptaSense, a company within the QinetiQ group, started business in 2008 initially with just a handful of employees. It has now grown to over 160 people. QinetiQ brought together decades of sonar signal processing expertise and capability from the QinetiQ group with a new fibre optic distributed acoustic sensing technique from an external company called Sensoptics. The combined capability became OptaSense and is now the world’s  leading distributed optical sensing company with research, development and manufacturing based in the UK and the majority of its products exported around the world.

The OptaSense DAS system injects a 1550 nanometre wavelength pulse of light into the fibre 2,500 times a second. The fibre length operated by a single device is typically 40 km and is a single-ended system.

DAS works on the principle that no fibre is perfect and throughout the length of the cable, there will be minor perturbations that cause small reflections of light that in the quiescent state show up as tiny peaks on a computer screen at the measuring end. The unique pattern of these peaks allows the fibre to be graduated into sample points. These can vary between every 1- 15 metres, although typically the measurement section is 10 metres. Over a 40km length, some 4000 measurements of the fibre can be interpreted which pinpoint any event along the cable with considerable accuracy.

Practical realisation

So far, so good – but interpreting events needs to be taken a step further. Along a 40km length some events will happen on a very regular basis; road vehicles passing over or under the track on a bridge, a level crossing for either road or foot users, an access walkway alongside the track, and such like.

To prevent alarms being raised every time a routine event happens, the alarm for that 10 metre zone can be disabled and it would be the customer’s choice as to whether every occurrence was recorded.

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Another differentiator will be the type of acoustic energy detected and the pattern recognition that this generates. Thus someone digging a hole will be seen as different to someone using a hacksaw. The customer might choose to alarm for one but not the other, based on their threat profile.

Being able to present events in a manner that can be easily interpreted at the control point is a crucial element of the system. With so much data being collected and stored, it would be tempting to over-provide information to the controller, thus causing bewilderment and confusion as to what is exactly taking place. OptaSense has therefore put considerable effort into making the monitoring screen user friendly and providing operators with Decision Ready DataTM.

A variety of data options is available, and the choice will depend on the type of control point being used. In a Traffic Management or Rail Control Centre, where the operations staff have other duties to perform, it might just be a simple alarm that triggers an interrogation by a member of the technical support staff. In other implementations, the system is integrated into the process control systems directly and activates prescribed actions e.g. changing signals or sending a preset message. What is important is that an event can be accurately detected, classified and located in real time. This information is presented in a decision-ready format to allow the appropriate response, for example the dispatch of a team to investigate onsite or a police call out.

To demonstrate the capability, OptaSense has run out a 3km length of buried fibre optic cable around its Winfrith facility, part of which is runs alongside the Poole to Weymouth rail line just to the west of Wool Station. This cable is linked to a typical monitoring station setup complete with CCTV.

In a demonstration of the remote monitoring capability, two-way radio was used to instruct a person outside to perform a number of threat scenarios such as cable theft. The results were all immediately visible in the monitoring station.

The proximity of the site to the southern boundary of the Poole – Weymouth rail line means the passage and health of trains passing along this line can be monitored. OptaSense believes it would be perfectly possible to link the system into a spare fibre of the FTN cable and thus monitor events on the line over a 40km distance.

Experience to date

Systems have been installed to protect over 13,000km of asset worldwide, most of which is oil and gas pipelines but the technology is currently monitoring on approximately 500Km of rail line and 100km of roads.

In the rail sector, systems are currently deployed on Deutsche Bahn (Germany), ÖBB (Austria), and two major US railroads. Other projects include underground metro lines, European high speed lines, African rail lines as well as Australian rail freight lines associated with the mining industry. Most interestingly, DB and OptaSense recently announced a collaboration to evaluate whether

DAS technology could replace a number of conventional trackside sensors thereby reducing the cost associated with track monitoring. Under the collaboration, a total of 25 different test scenarios are being investigated including SIL4 applications (safety integrity level 4 – the most dependable level of European Functional Safety Standards).

Future potential

Customers who have experience of the OptaSense systems are enthusiastic about potential uses beyond the current ones of train or vehicle movement, rock fall, cable theft, wheel flats and presence of people. There are aspirations to move up the SIL ladder with perceived applications being:

» Hot axle box detection by noticing a different sound of one axle compared to others;

» Train integrity by continually counting axles as the train progresses;

» Monitoring the operation of point machines or level crossing barrier motors by detecting changes in machinery noise to detect potential failure;

» Improving user-worked crossing safety by giving time before the train arrives;

» Train positioning information as a feed into signalling systems.

All long linear asset industries know the trade-off between the desire to monitor the whole length of an asset (rail, road, pipeline and border) and the prohibitive cost that this would entail using conventional technology. OptaSense has a vision to build the Earth’s Nervous SystemTM where these assets – the arteries of global commerce – are protected and managed. This vision appears to be both achievable and affordable.

Sand and ballast don’t mix

Although ballasted track remains the conventional method of constructing railway lines, the system is susceptible to ballast contamination in desert and wet areas as well as high-wear in heavy use applications. This can lead to high maintenance costs and, sometimes, even track failure.

Since the 1950s, ballast-less track systems have evolved for specialized applications such as high-speed rail and tunnels, but at a significant initial cost premium. What is needed is an affordable solution for areas with poor ground conditions for which conventional ballasted track is not suited.

Ballasted or ballast-less?

Conventional ballasted track consists of cross-lying timber, steel or concrete sleepers on a ballast bed of crushed quarry stone which in turn lies on a wide earthworks formation. Essentially, it is a bridging system whereby sleepers resident on resilient ballast are bridged by rails that are strong (heavy) enough to accommodate the bending stress required by the train’s axle load specification.

Ballasted track is expensive to maintain given that it contaminates easily, requires access to quarries and ballast supply trains and has to be cleaned and renewed using specialised machinery. All of these can present significant challenges to those responsible for railway construction and maintenance in developing countries and in areas of difficult terrain.

Different ballast-less track systems are available and being used around the world, mostly in the category of track slab systems. These include systems with discreet rail support, such as a hand-laid reinforced concrete slab with baseplates; RHEDA2000 – where standard sleepers are cast into a continuous slab; Sonneville Low Vibration Track (LVT) and the Japanese reinforced concrete roadbed system (RCRS) that uses precast concrete slabs.

DSCN0123 [online]Ballast-less track systems with continuous rail support include Paved Concrete Track – PACT and Embedded Rail Structure (ERS) where the rails are embedded in an elastic boot, cast into a continuous concrete slab.

Longitudinal support

The technological debate between continuous vs. bridged support of rails has some of its origins in Brunel’s “Baulk Road” system installed in the 1800s on the Great Western Railway in the UK. In these systems, each rail is supported along its entire length by a baulk or longitudinal sleeper. Gauge is maintained by the use of tie-rods between the two baulks.

The T-Track system, privately developed in South Africa since 1989, is a ballast-less track system that competes on an equal footing with conventional ballasted track on initial and major upgrade costs, whilst maintaining the substantial cost advantage of ballast-less track. It is an integrated track system comprising both the track substructure, characterised by narrower layer works (compared to conventional ballasted track) and the track superstructure, characterised by a modular articulated beam-track arrangement.

Track modules

The basis of the T-Track system is the track module. This consists of a pair of reinforced concrete beams which are wet-cast into geotextile bags and separated by gauge bars. Stirrups take conventional rail fasteners (Pandrol, Vossloh, Unit Rail) and continuous pads along the length of both beams provide a resilient base for the rail itself.

The modules sit directly on a prepared formation that is narrower than that required for ballasted track and are grouted into place. The design and stiffness of the modules and the formation is carefully calculated using finite element analysis to obtain the optimum performance and support for the track modules.

There are three basic designs of module. Tubular Modular Track (TMT) is used on straight and curved sections. Modules are precast using the same mould.

Modular Tubular Turnouts (MTT) are precast in sections using a double-sided mould to accommodate left and right-hand turns. Modular Tubular Level Crossings (MTLx) – these are an adaptation of TMT using precast inserts which fill the void between the beams to establish the level crossing.

All three types are available for standard gauge (1,435mm) and narrow gauge (1,067mm and 1,000mm) although other designs are perfectly feasible. MTTS are designed for UIC and voestapline VAE designs for 1:9, 1:12: 1:20 secant and tangential turnout sets, and will soon be availiable for the range of Vossloh turnouts.

System design

The T-Track structure is designed using a conservative 2D model to an ultimate limit state (including fatigue). This is verified against a 3D model concurrently during formation design. The serviceability limit state is set at soil deformation. 3D tie beam design and analysis is verified by hand calculation.

Design considerations include the required axle load and speed, rail size and the underlying soil stiffness.

The rail-track with the formation is modelled, with three dimensional (3D) finite element models (FEM), to determine the stresses and deflections (behaviour) of the track structure. The FEMs are solved with a transient dynamic solver, with the linear elastic material properties with damping coefficients for the system with moving load applications.

Image2 [online]The FEM has been calibrated extensively over a number of years for heavy haul operations by the Transnet Freight Rail Track Test Centre in South Africa, as well as the University of Pretoria using measurements from instruments such as pressure plates/ cells at the interface between formation layers and multi-depth deflectrometers (MDDs), typically at three stations, with three holes per station and six MDDs per hole.

In use today

T-Track exhibits a low initial cost and overall lowest total cost of ownership when compared to other track systems. Project cost compares favourably with ballasted track, but has lower maintenance cost, exhibiting a doubling in rail and turnout life and an improvement in weld life. The impact of Tubular Modular Track on project cost is significantly less than slab-track, as it requires a narrower formation as ballasted track. Tubular Modular Track project costs decrease with increasing use over the length of track, as less transitions are required and economies of scale in manufacturing and installation logistics increase.

The ballast-less T-Track system represents a major cost breakthrough for use as a generally affordable rail track solution. It has developed a strong multi-disciplinary value proposition to displace conventional ballasted track and slab track systems in many cases.

And it is not new, unproven technology. 600km are in use in the mining industry while the first surface track was laid for freight traffic in 1990. Since then there have been many successful applications in South Africa, USA and Canada with some installations conveying in excess of 80 million gross tonnes per annum with axle loads of up to 32 tonnes.

Turnouts have been in operation at Ermelo Coal Yard since 2000 without any significant maintenance and have now carried more than 950 million gross tonnes.

Ideal in sandy environments, the first T-Track was installed in Saudi Arabia in 2008. Not only does it remain perfectly resilient, it has maintained its original geometry within 2mm tollerance. Today, having endured some 125 billion gross tonne kilometres in extreme conditions over many years, this technology is now fully proven and certified for operations.

With its lowest cost of ownership and scalability into large projects this technology could well revolutionise the way rail track, especially on freight lines and in difficult terrain, is constructed in future.

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