Glasgow Queen Street station – half transformed

31st January 2019

Rail Engineer has reported on numerous infrastructure upgrade projects to provide the extra and longer trains needed for increasing passenger numbers. This extra traffic also requires station enhancements to provide space for passengers to move as well as providing a more attractive passenger environment and stimulating developments in the vicinity of the station.

Recent examples are London King’s Cross (2012), Birmingham New Street (2015), Manchester Victoria (2015) and Edinburgh’s Haymarket station, which had its passenger circulating area increased tenfold (2013). Now Glasgow’s cramped Queen Street station is about to be transformed. As will be seen, enlarging this relatively small city-centre station is a challenging project.

The Edinburgh and Glasgow Railway

Queen Street station opened in February 1842 as part of the Edinburgh and Glasgow railway, which then operated four trains a day between the two cities with a journey time of 2½ hours. The railway company had originally intended to approach Glasgow by a bridge over the Monklands canal and build a station just north of the present station. However, the canal company’s opposition to this idea resulted in Queen Street station, which is approached down one of the steepest parts of the UK rail network, a tunnel under the canal with a 1 in 44 gradient.

Although the canal is long gone, its legacy of a cramped station at the end of a steep tunnel remains. The original Queen Street station soon proved woefully inadequate for its increasing traffic and it was rebuilt between 1878 and 1880, with the tunnel being shortened by 153 yards to create a new station throat and platform extensions. The wrought-iron arched roof was also built at this time. As part of an East-West line under the city, the low-level station was excavated underneath the original station and opened in 1886.

The nearby Buchanan Street station closed in 1966, which resulted in Queen Street becoming the terminus for destinations north of Glasgow as well as the main line to Edinburgh. Whilst this may not have been a problem at the time, the station is now too small for its 16.4 million passengers each year who make it the third busiest in Scotland.

The capacity of the Edinburgh to Glasgow main line was significantly enhanced when, first, its train service was doubled to four trains an hour in 2000 and then, shortly afterwards, six-car Class 170 DMUs were introduced on the route.

Yet, just nine years later, this was still not enough as, in 2009, the Scottish Government published its Strategic Projects Review. This concluded that increasing rail capacity between Edinburgh to Glasgow was a high priority and proposed electrification and six trains an hour on the main line between the two cities.

However, this was a costly proposal that required significant infrastructure works including a grade-separated junction at Greenhill and a new chord at Dalmeny. In 2012, the then Scottish Transport Minister announced a revised scheme that did not require these infrastructure works as the required extra capacity was to be provided by longer trains rather than increasing service frequency and that this new approach was due to “new opportunities”.

*View of station from Buchanan Galleries during 2016 blockade.*

EGIP

One of the new opportunities concerned the Buchanan Galleries shopping centre, immediately north of Queen Street station. In 2011, its developers unveiled plans to expand the centre that would provide the station with an opportunity to extend its platforms to accommodate eight-car trains.

Hence, it was decided that the required extra capacity would be provided by longer trains instead of by increasing service frequency. In addition to the Queen Street work, this would require platforms to be lengthened at four intermediate stations on the route. This work was done as part of the Edinburgh to Glasgow Improvement Programme (EGIP), which has also electrified the route, rebuilt Haymarket station and built a new train depot at Millerhill.

The EGIP programme required two major blockades on the route. In 2015, Winchburgh tunnel clearance work requiring the installation of slab track closed the tunnel for six weeks.

In 2016, the tunnel into Queen Street was shut for twenty weeks to replace its life-expired slab track, install OLE conductor bar and remodel the station’s track and platforms. This remodelling required 165 metres of new track, seven new switch and crossing units and 642 metres of new platform walls. At the same time, the new OLE infrastructure was installed within the station environment.

This work enabled Queen Street to accommodate seven-car units when electric trains started running on the Edinburgh to Glasgow line in December 2017. An eight-car service, however, awaits the completion of the Queen Street station rebuild. Before this work could start, an order under the Transport and Works (Scotland) Act (TAWS) was required to give Network Rail the necessary powers, including those to demolish buildings and purchase the land on which they stood.

*Consort House and the Millennium Hotel extension before their demolition.*

TAWS

The redevelopment for which the TAWS application was sought extends the station southwards to front onto West George Street, on the corner of George Square, as well as the redevelopment of the east side of the station. This required the demolition of station facilities on the east side of the station, the seven-story Consort House office block of brutalist concrete appearance and a bedroom wing extension to the Millennium Hotel which was within the 20-metre overrun risk zone beyond the buffers – of particular significance as trains approach the station down its steep tunnel.

The station is in the Glasgow Central Conservation Area and the train shed, with its iconic iron arch, is a grade A listed structure while the Millennium hotel is grade B listed. Consort House and the hotel extension were built during the late 1960s / early 1970s. The project’s environmental statement notes that these buildings were of “minimal architectural and historic interest” and that “they are of a dated and generally poor appearance”.

Consultation for the TAWS application took place in 2014. This resulted in changes to the draft order, which was submitted in September 2015.

It was then considered by the Scottish Government’s Planning and Environmental Appeals Division (DPEA), which had to consider objections to the order of which the most significant was from the owner of the Millennium hotel – concerned at the loss of 51 bedrooms from the demolition of its extension.

Published in October 2016, the DPEA’s findings concluded that the demolition of the hotel extension was unavoidable as the station works were necessary and had been clearly justified in the public interest. The report included some minor changes to the order and various conditions, including the requirement for a Code of Construction Practice.

Following further consideration of responses to the draft, the TAWS order was finalised and came into force on 11 April 2017. This was nine months later than had been anticipated in the consultation leaflet, which had stated that the work would take three years. With the TAWS order now in place, Network Rail was able to start the Queen Street station enhancement works and announce that it would be completed in March 2020.

However, whilst the TAWS order was being considered, Land Securities, which owns the Buchanan Galleries, placed its £390 million development plan on hold “due to the increased level of risk generated by the simultaneous delivery of the EGIP programme”. As a result, the associated development of the east side of the station is no longer part of the current station enhancement work, other than its use for temporary ScotRail office accommodation during the work. Options for the use of this part of the station, including a possible Platform 8, are now part of a GRIP (Governance for Railway Investment Projects) study which is at stage 2 (project feasibility).

Work starts

In April 2017, Balfour Beatty was awarded a £16 million enabling-works contract for the station’s redevelopment. In August, it was announced that the company had been awarded a £63 million contract to demolish buildings and build the new station. This is a target cost contract in which any gain/pain is equally shared between Network Rail and the contractor and any exceedances over ten per cent are wholly borne by the contractor.

The project’s principle designer is Arup, with BDP architects acting as architectural sub-consultants. Key sub-contracts placed were demolition (Dem-Master), scaffolding (Lyndon), piling (Roger Bullivant), steelwork (J&D Pierce), cladding and roofing (Curtis Moore), curtain walling (Charles Henshaw), railway and frangible decks (Story Contracting) and mechanical, electrical and plumbing (Balfour Beatty Kirkpatrick).

The enabling works included the demolition of the accommodation block on the east side of the station and preparation for the demolition of Consort House and the Millennium hotel extension. At the same time, a pub on Dundas Street, by the west entrance of the station, was converted into ScotRail’s ticket office to be used for the duration of the work.

On 7 August 2017, the station work became evident to passengers as the ticket office was transferred to this temporary office, the station’s southern entrance was closed, and hoardings were erected around the demolition area. At the same time, traffic on West George Street was reduced to a single line with one lane becoming part of the worksite to be used for the receipt and despatch of lorries.

The old ticket office was part of the west-side office accommodation by Platform 2 that was demolished later that year to create space for the extension of Platform 1. Much of this was completed during the Christmas closure of the station in 2017.

Consort House was then fully scaffolded and covered with protective sheeting. In January 2018, lightweight excavators were craned 36 metres to the roof of Consort House to start the top-down floor-by-floor break up of its reinforced concrete and steel frame. At the same time, long-reach excavators were used to demolish the hotel extension.

By March, this enabled the station’s historic train shed to be seen from George Square for the first time in forty years. However, this also exposed it to a wind loading for which temporary work was needed to stabilise the structure. Another revealed aspect of the station’s heritage was the words “North British” on the hotel’s newly exposed end wall, which was surveyed by drone in July.

By the time the demolition work was completed in October, 14,000 tonnes of material had been removed from the site, requiring around a thousand lorry movements. A crushing plant was used to enable 94 per cent of this to be recycled.

The project achieved its first delivery milestone on 7 May 2018 when the extended Platform 1 was brought into service. This had been extended by 50 metres to accommodate four-car trains using the space created by the demolition of the west-side offices.

Over half-way there

On 26 November, Rail Engineer was pleased to visit the project and meet Network Rail’s route delivery director Kevin McClelland, programme manager Tom McPake and project manager Joe Mulvenna, as well as Balfour Beatty’s senior project manager Barry Nicol. At the time, the project was on schedule and 86 weeks into its 154-week programme.

The project briefing included safety management arrangements, which included Network Rail’s involvement in briefing and reporting arrangements. Barry and Kevin emphasised how such close collaboration was typical of the project’s open and honest working arrangements.

*Completed demolition work seen from above the temporary ticket office in October 2018.*

Kevin advised that the sub-contractors were generally based within a 30-mile radius of Glasgow. He noted that using local suppliers enables the project team to visit companies, such as Glengarnock-based J&D Pierce which is supplying the structural steelwork, enabling him to monitor progress much more easily than if he was working with someone based at a remote location. There is also the associated environmental benefit of a reduced carbon footprint through shortened travel and delivery routes to site.

It was also stressed how the project had benefited from the single three-dimensional model produced as a result of working to BIM level 2. This had provided walk-throughs using virtual-reality headsets, which had proved to be very useful for visualisation and consultations. It has also avoided both design and construction clashes, especially when planning the later stages of the project when different sub-contractors will be working in close proximity.

The sub-surface station on the low level is not directly affected by the works. However, its fire and evacuation arrangements must be maintained and there are weight restrictions above its tunnels. Joe Mulvenna described the challenges of working in such a constrained site, with only one entrance for vehicle movements, while maintaining the operational integrity of a station with 45,000 daily passenger movements.

To ensure effective liaison with the station, Network Rail has funded a full-time ScotRail representative who is dedicated to the project. Joe also advised that there is excellent liaison with the Millennium hotel, with work being carried out in accordance with the Code of Construction Practice to minimise disruption to the hotel and other affected parties.

Tom described how community engagement is an important aspect of the project. He noted that the project’s Twitter account has nearly 3,000 followers, many of whom followed the demolition works with close interest. In July, the project commissioned local artist Gabriella Marcella to produce colourful artwork on the project’s hoardings that were inspired by the Glasgow coat of arms.

Rail Engineer’s tour of the station started on its cramped concourse, where a small area has been hoarded off at the end of Platform 5. This is being used for work at night for the removal of asbestos lagging from pipes that run along the buffer stop ends below the concourse. These pipes and other services must be moved to allow the extension of Platforms 2 to 5.

In the worksite outside, there was a large amount of empty space around the train shed following the completion of the demolition works. One aspect that was not evident to the public was the depth of the area south of the train shed. In the two months since the completion of the demolition work, piling and basement works had created a level four metres below street level that will eventually accommodate the station’s toilets, left luggage office and plant rooms.

Also visible were tracks at the western end of the low-level station where an old concrete deck had been removed over Christmas 2017.

*Basement under construction where Consort House once stood.*

The remaining work

Barry advised that visual progress of the work will soon become far more rapid as the steelwork around the train shed is built up. This started with the erection of the 74-metre-long west truss, which was installed in three parts by a 750-tonne crane on the night of 15 December. In January, a tandem lift by two 500-tonne cranes will erect the south truss. By April the remainder of the steelwork, 1,400 tonnes in total, will have been installed around these trusses.

*Part of west truss being lifted into position. (Peter Devlin)*

This will then enable cladding and roofing works to commence. By October, all the cladding will have been put in place, comprising of the following types of cladding: Eurobond and Kingspan wall (3,200 square metres), stone (1,300 square metres) and anodised gold (3,000 square metres). The roofing is 3,100 square metres. The curtain walling, which includes 500 square metres of glazing, will be completed by December.

By the summer, this station envelope work will enable the concourse to be extended to enable the platform extension work to take place. To avoid disrupting train services during the Edinburgh Festival in August, this will be done in two four-week stages in July (Platforms 2 and 3) and September (Platforms 4 and 5). This work involves new buffer stops and the frangible decking behind them, concourse substructures, drainage, service diversion and OLE work.

When complete, this work will extend Platforms 2, 3, 4 and 5 to accommodate eight-car trains – Platform 7 can already accommodate them. This will achieve the key milestone of having all extended platforms in use so that eight-car trains can be introduced with the December 2019 timetable change.

The last station work is the plant fit out and its associated mechanical and electrical work, which will be ongoing between April 2019 and March 2020. This programme is planned to meet the project completion date of Spring 2020.

*BIM graphic showing west and south trusses.*

EGIP phase 2?

The completion of Queen Street station will also mark the end of the Edinburgh Glasgow Improvement Programme, which has delivered 150 single track kilometres of new electric railway, redeveloped three stations and built one more, constructed one depot and remodelled another as well as extending platforms at four stations.

Before the EGIP programme, the main Edinburgh to Glasgow line carried four 6-car diesel trains an hour in each direction between the two cities, each having 396 seats and completing the journey in a minimum of 49 minutes. The current seven-car electric trains have 479 seats (21 per cent more) and do the journey in a minimum 47 minutes. Once Queen Street’s platforms are extended, the December 2019 timetable will see eight-car trains with 546 seats (38 per cent more than the diesel train) covering the distance in 42 minutes.

In addition, Glasgow is to get an iconic city-centre gateway station to replace one hidden from view from its main square, which will no doubt provide a stimulus for further development. The station’s passengers will also benefit from improved facilities, including a concourse increased from 960 to 1,800 square metres.

Although it would seem that EGIP is almost complete, the planning and execution of this programme to deliver a 38 per cent increase in capacity has taken about ten years. Yet, in ten years’ time, passenger numbers between Edinburgh and Glasgow are projected to grow by a further 40 per cent, so maybe now is the time to start planning EGIP phase two to provide six trains an hour by 2030!

Timing of door closure – how critical is it?

30th January 2019

Passengers inside a London underground train. — London, England - March 5, 2016: Some passengers inside an underground train arriving at Picadilly Circus station in London, England.

Much has been written and said in recent times about efforts to improve the throughput of trains on metro and inner suburban railways. Using CBTC has enabled 36 trains per hour (tph) to be achieved in each direction on London Underground’s Victoria Line. A dramatic improvement to passenger comfort has resulted and much of the severe overcrowding has been eliminated. Similar predictions are made for other LU Lines and also the full Thameslink and Crossrail (Elizabeth line) services when they reach full fruition.

However, a crucial factor in all of this is the ‘dwell time’ at stations to allow travellers to alight and board the trains. If the time taken for this overruns by more than a few seconds, then very quickly the delay to following trains builds up and the intended throughput becomes unachievable.

A service gap of more than three or four minutes means that crowds increase on the platform, extending the dwell time at every station as they attempt to board the first train, compounding the problem.

Although, in theory, drivers are not supposed to initiate door closure until everyone is safely on board, in practice, they occasionally have to start the closure process whilst people are still squeezing in, otherwise the train would never get underway.

A further factor is now influencing the process, this being to take account of the needs of disabled people, with legislation potentially increasing the dwell time period. Whilst the Rail Vehicle Accessibility Regulations (RVAR) of 2010 (its forbear being the Disability Discrimination Act) is intent on allowing additional time to board, the basis of this prescription may not have been scientifically derived, with perhaps a less than optimum situation developing.

London Underground was concerned that a negative impact could result and initiated a trial to establish exactly how passengers behave when boarding tube trains. Rail Engineer went along to learn the facts.

Door closure sequence

When a train arrives at a station, providing it is proved stationary and at the right location, door opening is initiated by the driver. After passengers have alighted and boarded, a door closure alert signal (known as a Chime) sounds for a period before the doors begin to close. Providing nothing is trapped in the doors (see later paragraph), the driver’s door close pilot light illuminates and the train start buttons can be pressed for ATO equipped lines or the driver engages traction power if driving manually.

The chime signal time is crucial. The LU standard is 1.75 seconds ± 0.25 seconds, whereas the RVAR (aligned to the Equality Act) requirement is three seconds. This difference, whilst small, can accumulate to several seconds for an end-to-end train journey and, if applied to every train, can significantly reduce the overall service throughput. More importantly, however, does changing to three seconds make any detectable difference to either non-disabled or disabled passenger behaviour?

One important element is the ‘hustle’ effect. When the door chime sounds, a regular occurrence is for passengers to hurry into a nearby door so as to avoid waiting for the next train.

Regular commuters are adept at knowing which door is nearest to the exit at their destination station, so they will not always board a train when it arrives but instead continue to walk along the platform to the preferred door. If the chime sounds before they get there, they jump in through the nearest open door.

Equally, travellers who are not regular underground users and who may be tourists from another country, on hearing the chime, will rush to the nearest door, often with large amounts of luggage.

Any instance of incomplete boarding will result in a door obstruction situation and potential train delay. As a door obstruction takes a minimum of five seconds to resolve, the delay impact can be significant if compounded along the route. On the Victoria line, any door obstruction incident is automatically flagged within the train software and sent by Wi-Fi to the server, available for review by engineers within 20 minutes.

Different marques of Underground train have differing solutions to this situation. The most modern trains (Victoria line 2009 stock and the S stock units on the sub-surface lines) have obstruction detection whereby, should an obstruction occur, the door will reopen part way to allow the obstruction to be pulled clear.

They also have sensitive door edges where any deformation of the door edge will cause an emergency brake application should the train have started to move. This deformation can be caused by even very thin items which, when caught, would be pulled on as the train begins to move.

Older trains are designed to ensure doors are fully closed before traction power can be applied. However, this system is not foolproof and thin items such as bag straps or coat belts can be trapped between the doors and are not always detectable. Unfamiliar users often expect the doors to re-open if an obstruction is detected, much as they do on lifts, but this is not true for Underground trains or indeed any UK train with sliding doors.

All of this presents a complex set of circumstances that, when combined with the differing views on chime time, meant that a comprehensive trial was necessary to understand more completely the impact on passenger behaviour and minimising the ensuing risks.

*Two groups of risks associated with the door closure sequence.*

The trial

To be meaningful, plans for any trial must define what it sets out to do, the way it will be measured and how the results will be analysed. The intent of this exercise was to assess the impact of different door chime timings with respect to the following aspects of door usage and passenger behaviour: safety, accessibility and capacity (in that order).

The trial, which took place on the Victoria line, consisted of a number of investigations within the context of both a 1.8 sec and 3.0 sec chime duration, covering:

Door obstruction data, collected from the rolling stock;
Platform observations;
Reported safety incidents;
Passenger survey;
Service data (dwell times, lateness).

The door obstruction data ended up being the most meaningful in terms of assessing safety: it was used as a proxy for the number of passengers being struck by the doors, an indication of items that could be trapped (risk of dragging), and an indication of the number of passengers running (risk of slips and trips). If LU’s concerns about the hustle effect were correct, an increase of door obstructions would be observed.

To be effective, the trial needed to ascertain the before and after situation, so data and observations were obtained prior to August 2017 after which the chime duration was changed to three seconds for a period of six months. The whole Victoria line fleet of 37 trains, each of eight cars, was altered so as to get consistency and to accurately observe passenger behaviour. The results have proved interesting.

*A schematic of how the balance of the two types of risks can result in the lowest overall risk.*

Results

The door open and close sequence was found to be well disciplined at peak hours, with regular travellers standing clear of the doors before getting on in order to allow passengers getting off to disembark more quickly. During off peak periods, however, unfamiliar travellers tended to block the door egress, thus slowing the whole process. A longer chime duration did allow more time to get out of the way of the doors, but equally gave more time to try and board.

The sounding of the chime has always been known to prompt late boarders to run for the nearest door. With 1.8 seconds, the time was insufficient for this to be successful unless very close to a door. Extending the time to three seconds saw an increase of the hustle effect with the result that noticeably more door obstructions occurred. This worsened the safety risks as more doors were striking or trapping passengers, the numbers of trips/falls increased and more pushing/obstruction of other travellers took place.

Clearly there is a linkage between door obstructions and passenger demand, with the number of obstructions using a 1.8 sec chime remaining fairly constant throughout the year, rising slightly between October and the year end. Introducing the three second chime saw a marked increase in obstructions during the lead up to Christmas, during the January sales and at public holiday weekends.

The overall finding was that off peak, more people ran for a door once the chime sounds as the platforms are less crowded, whereas in the peak more people tried to squeeze in.

Not surprisingly, the highest number of door obstructions occurred at the busier stations. The northbound platform at Victoria was by far the worst, with an average of 245 obstructions happening each day during the three-second chime period, an increase of 60 (32 per cent) over the 1.8 sec time. Oxford Circus and Kings Cross also recorded high numbers of around 150, in all cases the longer chime time being marginally worse.

At less-busy stations, the effect was more prominent – at Highbury and Islington southbound in the morning peak, the obstructions rose 80 per cent with the extended chime time and an overall increase was noticed throughout the day.

The door obstructions were also markedly different down the length of the train. At Oxford Circus (northbound), the problem mostly occurred at the doors in the second and third front cars, close to the exit for the concourse and interchange for the Bakerloo line, and at the rear end where people change for the Central line. The number of door obstructions were significantly increased with the three-second timing.

*The total number od door npt closed’ events recorded between 01/09 and 22/12 at Highbury & Islington Platform 5 for both 2017 (trial) and 2016 (baseline).*

Analysing the trial

Clearly the increase in chime time had a detrimental effect on obstruction occurrences and, due to the safety impact, the Victoria line fleet has since reverted to a 1.8 second timing.

That said, it has been necessary to submit the findings to vested interest groups. Presentations have been given to the London Underground hierarchy (DRACCT – Director’s Risk Assurance Change Control Team), to Transport for London (TfL), the Department for Transport (DfT, in effect – the government) and the Office of Rail and Road (ORR – the rail regulator). The DfT has forwarded the results to the Disabled Persons Transport Advisory Committee (DPTAC) and other stakeholder groups.

A passenger questionnaire has been conducted in an attempt to establish what passengers believe are the safety risks associated with their journey. Approximately 150 responses were received, which is considered sufficient to gain some understanding but is a very small sample compared to the approximate 75 million passenger journeys made on the Victoria line during the period of the trial.

Of these respondents, 60 per cent considered themselves to have a disability. Oddly, the time to board and door closure time feature less than the fear of interaction with other passengers who might, in their urgency to board, push people both on the train and on the platform. There was little difference in the responses from both disabled and non-disabled passengers.

Overall, the trial findings have been well received, since there is now hard proof that the three-second chime offers little improvement to accessibility and has a negative impact on safety. The recommendation from LU is that the standard should remain at 1.75 ± 0.25 secs, and this is being considered by the aforementioned bodies.

London Underground stresses the point that it is totally committed to improve accessibility across the entire network, with step-free access being provided at an increasing number of stations and large projects underway to improve accessibility.

*Victoria line at Victoria station. (Muhammad Junaid)*

Factors for the future

It may be asked how this trial impacts on other metro/light-rail operators and, indeed, mainline suburban services. Main line operation is different in that it provides timetabled departures rather than a high-frequency, turn up and go service, and as such passengers have more time to plan their journey and associated timings at a station. That said, the likes of Thameslink and Crossrail (Elizabeth line) may be more akin to LU operation in the central London sections.

The eventual adoption of fully automatic trains (Unattended Train Operation – UTO) may well become reality. They exist already on the Paris Metro (Lines 1 and 14) where door operation is programmed automatically, dependent on the particular station and the time of day. When the programmed time has elapsed, the doors will begin to close regardless of whether boarding is still taking place or not. Centralised CCTV monitoring of conditions takes place both on platform and train so that remote intervention can happen should anything untoward occur. Travellers have got used to this and it is now part of normal life.

The current modernisation of the Glasgow Subway will adopt UTO when completed in the early 2020s.

In all, this trial demonstrated the many complex interactions that take place at the platform-train interface. As the population of London increases, so the pressure to provide more and more public transport services will mount and the need to be up-to-speed with technology and optimum routines will become ever more vital.

Thanks to Zoë Dobell, LU’s project engineer for the trial, for this fascinating insight.

GSM-R: a migration strategy to its successor?

30th January 2019

Abstract Creative concept vector background for Web and Mobile Applications, Illustration template design, business infographic, page, brochure, banner, presentation, booklet, document.

The thorny question of what should replace GSM-R as the future radio bearer for track to train communication has recently been the subject of conferences, discussions and, yes, even articles in Rail Engineer. Considerations of 4G, 5G and Wi-Fi options are being assessed, all having their pros and cons, and a few commercial interests have emerged as well.

Whatever and whenever the decision is made for the replacement technology, a major consideration will be how to migrate from GSM-R to its successor. Very little thought seems to have been given to this but Kapsch, as one of the leading suppliers of GSM-R infrastructure, presented a paper in London recently setting out the challenges involved and how they might be overcome. The logistics are somewhat frightening, but they nonetheless will have to be tackled sooner or later.

The present UK position

The GSM-R network in England, Wales and Scotland has been fully operational since 2015 and now comprises two MSCs (Master Switching Stations), 3,000+ masts and base stations, 9,500+ cab radios, 4,500 connected trains and 900 signaller terminals, all covering some 15,000km of railway. It’s quite an impressive portfolio, but having to change it all over to something else will need a very carefully thought out migration plan.

The GSM-R industry group has confirmed that it will support GSM-R until 2030, which sounds a long time off but, in reality, is only just over 10 years. In project terms, that deadline will come all too soon.

The Future Railway Mobile Communication System (FRMCS) study, being led by the UIC (Union Internationale des Chemins de fer – international union of railways), is making progress with developing a functional specification that the new radio network will need to provide, which is good news, but it offers little advice as to how this might be delivered.

It now seems likely that 5G will be the chosen way forward under the 3GPP R15/R16 (third generation partnership project) terrestrial coverage specification, but this has still to be confirmed. Some requirements are, however, sacrosanct – there must be bearer independence for railway applications, the system must have high robustness and high availability. Those requirements are easily said, but they are not so easy to quantify within a specification.

Functionality

The emerging vision for the new radio system is looking at three areas:

Critical communications – the bearer for ETCS and ATO operation, secure voice communication between driver and signaller, provision for emergency and group calls, real-time video imagery for any occurring incidents;

Performance communications – on-train telemetry, maintenance of non-critical infrastructure, non-critical real-time video, wireless communication for on-train-staff, on-train voice announcements;

Business communications – applications including information to the public and passenger communication connections.

These are listed in order of priority and it may not be possible to deliver all of them at the same time in any migration plan.

However, the FRMCS thrust is to have a single network under the railway infrastructure manager’s control for all safety critical application, but also to allow greater flexibility between dedicated rail and public network operators for performance and business applications. Indeed, it is seen as very likely that business applications will be entirely given over to public operators.

This mix of networks might entail having a ‘Mobile Communications Gateway’ as part of the on board system.

Radio spectrum

GSM-R enjoys a European-led dedicated allocation in the 900MHz band, comprising both a 4MHz uplink and downlink bandwidth, which is now recognised internationally. Recent channel allocations adjacent to these have created some interference problems but improved filtering has largely overcome the problem.

Knowing the future challenges that a migration will cause and the wider use of radio for other purposes, the EU has made a declaration to allocate an additional 2 x 1.6MHz of spectrum adjacent to the present GSM-R uplinks and downlinks. This will be critical to any migration plan as it should permit in-band co-existence of present and future services.

The present GSM-R infrastructure is built around 900MHz operation, with radio masts and towers sited for the coverage patterns of that band. The possibility of having both multiband and wideband aerials on the same sites could cause problems with mast loading, so engineering calculations will be needed. Appropriate separation of aerials on the tower or mast will be sensitive to avoid unwanted interference.

Train aerials, which can be a challenge to fit on the different classes of rolling stock, should ideally be capable of being used for both old and new systems if the spectrum allocation is the same, but there are technical challenges to this which may mean more than one aerial. No change to the permitted radiated power limits is expected.

A special case for deploying 5G technology in the 900MHz band will be needed, as this is not currently permitted for public 5G usage. It may be necessary to provide some additional radio sites to minimise interference from neighbouring users and to create additional traffic-handling capability by having smaller cells.

There is also the potential for having FRMCS services moved to either the 1900-1920MHz or the 2.3GHz bands. These might end up as complementary bands to provide additional spectrum to the 900MHz allocation. There may be complications in using these bands as different countries (including the UK) have parts of them allocated for other users and purposes.

There is lots of competition for spectrum allocation and it may require the railways to co-exist with other users. However, this would almost certainly mean that new infrastructure would have to be to be planned and it would create fitment problems on rolling stock, so, for now, it is not a preferred option.

*Adjusting a GSM-R aerial. (DB/Hartmut Reiche)*

Planning for migration

It is clear that any migration of this magnitude cannot be achieved overnight. The development of a 5G railway network is unlikely to produce new systems before 2023 at the earliest. Assuming all goes well, there will then need to be several years of co-existence of both old and new networks.

These sorts of challenges have happened before when planning changeovers involving both track-based and train-borne equipment. It is usual to either duplicate the infrastructure or duplicate the train kit, which is fine for a self-contained line such as a metro but much more difficult for a main line railway with many interconnecting lines and different types of rolling stock.

In view of these problems, Kapsch seems to be recommending a mix and match of duplication. Any plan must firstly concentrate on the critical communication need, primarily the bearer requirements for ETCS and voice communication to and from the driver. The former, although at first sight appearing to be the most important, will only have that status if ETCS with no lineside signals is the only control system for the line. If the ETCS is an overlay, then a more relaxed way forward might be adopted whereby, for a short period of time, trains are driven traditionally to whatever aspects are showing on the lineside signals.

By 2023, it is difficult to assess just how many rail routes in the UK will be operating with full ETCS Level 2 and no signals. Certainly, the Cambrian line, as that is already equipped in that fashion, and probably the southern part of the East Coast main line. Beyond that, it is anyone’s guess and much will depend on the roll out programme of the Digital Railway team.

It must be said that predictions for ETCS adoption over the past five years have been wildly optimistic, so any dates into the future should be treated with a degree of caution.

The Kapsch recommendation is that radio infrastructure would need to be duplicated in as short a time as possible, but concentrating on the ETCS-equipped routes as a priority. This will mean the provision of new core network elements, new base stations and, possibly, new aerials, with the necessary redundancy to meet the high availability requirements of the railways.

The next generation of network design will be much ‘flatter’ than at present, meaning that MSCs and base station controllers may disappear. Whatever the outcome, the new network must operate alongside the existing GSM-R network. Assuming the 900MHz band is continued, then the existing masts and towers would be suitable, subject to loading limits for new antennae.

Where coverage is provided in tunnels by radiating cable, then a means of mixing the old and new radio signals will need to be devised, but this should not be a major problem.

The new radio infrastructure will require a separate land-based network that, logically, will be based on IP communication, including all the backhaul links to and between the base stations. Clearly this network will need full resilience, synchronisation for both frequency and phase (PTP – Phase and Time Protocol), path asymmetry, accuracy of time stamp and packet delay variation, plus, of course, minimising the threat of cyber attacks. With regard the latter, the security offered by 5G should be markedly improved over GSM-R.

Even when decisions have been made on duplication, a carefully planned migration strategy will be required to manage the actual changeovers. Kapsch has come up with what is termed a ‘whitespace’ plan, whereby a wideband carrier is superimposed on to the GSM-R channel to enable the continuance of GSM-R services plus up to 5.6MHz of 5G operation. This would allow the gradual introduction of FRMCS services on to the existing GSM-R spectrum but assumes at least an additional 1MHz of bandwidth is allocated.

Included in this plan will be the smooth decommissioning of GSM-R frequencies, which can then be immediately used for FRMCS services, giving much more flexibility to the migration programme.

Rolling stock considerations

The retro fitting of rolling stock is both complex and expensive, regardless of what equipment is involved. The cab radios do not take up much space, so having to have two radios in the cab may not be as onerous as some retrofits.

As well as the cab radio, there will need to be provision of the train aerial(s), additional power supply requirements and a second train data radio associated with the ETCS kit. None of this will be straightforward and significant expense will be incurred.

The Kapsch view is that, once the decision on the new radio standard is finalised, then fitting the equipment to the trains should become a franchise requirement. It would also be advisable for any new rolling stock procured following the radio decision to be made ready for (or even provided with) two train radio configurations, including multiple aerials along the train.

Changeover en-route

With a mix of both infrastructure and train-borne kit, there will then be the challenge of which radio is used on the train depending on where it is on the journey. For the voice radio in the driver’s cab, this should not be too much of a problem as both radios will be powered all the time and it will be obvious which one is active to transmit or receive messages.

For the train radio provided for the ETCS equipment, however, the problem will require more thought since the ETCS movement authority (MA) will require a near-constant transmission of confirmation data from the control centre. In the event of non-receipt of the data within a few seconds, the MA will be lost and the train will automatically brake to a standstill until the MA is restored. Thus, the continuance of the radio signal must be guaranteed during any changeover from GSM-R to the FRCMS and vice versa.

The use of eurobalises to achieve this may be one solution, although it is a clumsy one as the changeover point will be altered from time to time as the radio infrastructure is updated. The reprogramming of balises to reflect the new condition will be an unwanted burden and therefore it is more likely that some on-air signal will need to be devised.

Capacity and priorities

The question is posed as to whether the existing 900MHz allocation, without any additional bandwidth being provided, could support both the GSM-R and FRCMS systems. This seems unlikely, hence the negotiations with the CEPT to obtain the additional 1.6MHz of spectrum.

Although the ETCS operation requires near constant reception, the bandwidth required for individual trains is low – about 4kbps. Even with many trains operating within one radio cell, the now proven and adopted use of packet switched data has considerably eased the problem for both old and new to be contained.

However, should any voice communication take place at the same time, and possibly from multiple trains, it is quite likely that insufficient spectrum will be available. In very busy areas, such as city centres where radio signals will spill over from one line to another, this is already recognised as a problem with GSM-R. One solution would be to re-engineer the cell structure so as to create smaller cells but, even with this, it is a complex engineering and coverage challenge and the chance of spill-over remains.

To provide all the services envisaged in the FRCMS specification would be unrealisable, so priority will have to be given to the critical communications services, with other usage being restricted. The business and passenger communication requirements might have to wait for another chunk of spectrum in another band to become available and/or agreement with other network operators to provide these.

As such, the case for additional spectrum is reinforced. Much will depend on how usage works out in practice and some traffic modelling will be necessary.

Some final thoughts

That someone is giving consideration to how GSM-R will be migrated to a new radio standard is commendable. It is not going to happen tomorrow and the first migration will probably not be until 2023. However, that falls within Network Rail’s CP6, which leaves no great time for the planning process.

There is a significant risk that this advice will be ignored. Many signal engineers have a real problem in understanding the importance of the radio link within the overall ERTMS provision. It is as if they think ‘it will always be there’, a dangerous assumption. Even radio planning authorities have been known to publish papers that state “the railways have GSM-R so all is sorted”.

The harsh reality is that, however much ETCS equipment is installed on both trains and control centres, if the radio link is unavailable and/or unreliable, then it is all a waste of time. Which should provide network planners with food for thought.

Thanks to the IRSE London & South East section for organising the presentation and to Pierre Tane from Kapsch for delivering the paper.