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Creating the UK’s first driverless railway

The first of the next-generation Stadler Glasgow Subway trains was unveiled at September’s InnoTrans exhibition in Berlin. Image credit: TAUT

Glasgow’s Subway stands out as something of an oddity in terms of urban rail systems, with many quirky engineering features that have shaped its development and operations. These legacy constraints are part of everyday life for owner and operator Strathclyde Partnership for Transport (SPT), but they also pose major challenges in the system’s GBP288m (EUR323m) modernisation that will see Unattended Train Operation (UTO) introduced in the coming years.

With 11ft 2in (3.4m) tunnel bores and a four-foot (1220mm) track gauge, the circular system that covers both north and south sides of the River Clyde is the world’s third-oldest underground railway – after London and Budapest. SPT’s Senior Director Charles Hoskins has overall responsibility for the 122-year-old system: “We have some unique challenges, so you really have to understand the history of your assets before you start
to modernise them.

“Looking back to the 1890s, the Victorians were building this fantastic underground railway in London, the Metropolitan line, so the well-to-do people of Glasgow had similar thoughts. There were genuine transport reasons behind that decision; it was all about congestion and road space and finding a different solution to the horse-drawn carts and trams of the time.

“So they built the Glasgow District Subway as it was known. It opened on 14 December 1896, but actually only for a day as they had an accident and clearly the signalling system didn’t work very well, so it shut the same day. But that claim third-oldest is because it opened for that one day!” It reopened the following January.

The twin tunnels were built between 0.76m and 1.8m apart and come together at the systems stations in a single 8.5m arch, using a steam engine located between West Street and Shields Road stations to haul a 10.5km (6.5-mile) continuous raised cable. Grippers underneath the original wooden-bodied trains pulled them around the loop, releasing the cable to bring them to a stop at any of the 15 stations. The maximum speed at the time was 15mph (24km/h) and a lack of crossovers on the main system to this day means there are no facilities for ‘laying by’ trains during quieter periods.

Additionally, as there was no cable haulage to the depot, vehicles were transferred to and from the running lines by a crane operating over a pit at the workshops, located between Govan and Ibrox stations. History books suggest that trains could be moved across in just four minutes – incredible for the time.

The first moves to modernisation

In 1923, the Subway passed to the Glasgow Corporation Transport Department, and in the following decade was converted to the current 600V dc electric third rail traction supply. However, where the tunnel walls encroach upon the track’s dynamic envelope to make it impossible to mount the live conductor rail next to the running rails, this has been raised to higher on the wall with special brackets to ensure rigidity.

The next major upgrade came in 1977 under a three-year project as the system changed hands again to the Greater Glasgow Passenger Transport Executive (a forerunner to SPT, formed as a statutory corporation on 1 April 1996). This included station modernisation, tunnel repairs, track replacement and upgrades to the electrification infrastructure. Reopening in its present form in April 1980, the Subway now had its first points as part of a triangular junction to connect the Broomloan depot.

This upgrade also marked the last use of the original 1896 rolling stock, replaced with 33 powered units built by Metro-Cammell, to which eight trailers were added in 1992. These were refurbished by Alstom in the mid-2000s. Examples of the original fleet can be found at the city’s Riverside Musuem and the Bo’ness & Kinneil Railway.

The unusual track gauge and tight tunnel bores limits cars to 12m lengths and the route has gradients as steep as 1-in-18 (5.5%) for the under-river crossings. It takes 24 minutes to complete a full loop of the line.

Describing these constraints, Mr Hoskins says: “One of the biggest challenges we face today was the size they built it. There are a lot of historical questions about why it was built to that particular size, with suggestions it was due to cost.”

Moving into the 21st Century

Although the Subway has served the city centre well for 122 years, concerns over the state of the fully-gated system’s assets, allied to increased operational and maintenance costs, required a plan for ‘ground-up’ renewal as the GBP18-20m (EUR20.5-23m) in annual passenger revenue doesn’t go very far.

Mr Hoskins continues: “A recent passenger survey by Transport Focus showed punctuality at 95% with our overall reliability sitting at 99%. So we try and keep that high reliability, and in terms of overall customer satisfaction we sit at 97% with 93% positive feedback on journey times. So we could say; ‘it’s fine, keep running as we are’ and go home.”

But nearly 40 years on from the last major upgrades, the cracks were starting to show. In 2011 SPT began planning for its current programme to address rising costs and to increase capacity: “You get to the 40-45-year period with the bathtub effect and you’ve got to look at a strategic intervention. You can’t just keep putting a sticky plaster on things.”

With a four-minute peak frequency, six trains on each circle, last year the Subway carried 12.7m passengers, down from a high of 14.7m at the turn of the century. These figures are “substantial” in Hoskins’ eyes, “but nothing in terms of the scale you see in some of the megacities”. The Subway has around 260 staff, 170 operational, and all maintenance is carried out in-house.

Mr Hoskins continues: “We were facing some huge challenges, but the main driver is always the customer. Standards and expectations are continuing to go up, so how do we retain our existing passengers, cater for the future and deliver an even better service at the same time?

“We’ve been pretty flat in patronage for a while. Our city’s not necessarily seen itself develop around the Subway, and sometimes the value of the system is underestimated by city planners in terms of access to highly reliable, high-quality, affordable public transport.”

Smart ticketing

So with a March 2012 commitment of GBP246m (EUR276m) from the Scottish Government, detailed planning for the five-pronged modernisation could begin. This investment is topped up with GBP42m (EUR48m) from SPT’s own resources and a business case was built around savings of GBP150m (EUR171m) over the next three decades, and increasing capacity to 17 million passengers per year over a similar timescale.

Mr Hoskins continues: “This was a major investment based upon five main workstreams: smart ticketing, station refurbishment, infrastructure repairs and renewal, rolling stock and control system replacement, and organisational change.”

Around GBP6.7m (EUR7.6m) has been committed to smart ticketing initiatives to make the Subway and SPT’s other operations fit for the modern age. “We were one of the first to introduce a full ITSO commercial scheme with contactless cards [in 2013],” Mr Hoskins explains, “and we are now looking at delivering these products to mobile devices.”

Over 160 000 smartcards have been bought to date and online sales more than doubled
in 2017-18. Over a quarter of annual and six-month season tickets are now purchased this way. The next step is to go mobile.

Developed by Nevis Technologies – a joint venture between SPT and Rambus Ecebs – a pilot that enables the purchase of tickets via Android smartphones has been tested by staff for around 18 months and is now in the hands of ‘friendly’ customers. Utilising Host Card Emulation technology, passengers can download a ticket to their device to enter, exit and move seamlessly through the system. (For more on HCE, see TAUT 952).

Station refurbishment

“The next thing we decided at the beginning was a full refurb of all 15 stations,” Mr Hoskins continues.

Around GBP50m (EUR57m) of the total budget has been allocated to these works, with comprehensive remodelling undertaken in line with contracts with leading British architectural firms, Austin-Smith Lord, AHR and AEDAS.

The first to be completed was Hillhead, in September 2012, after 14 months of work that included new escalators, improved signage and passenger information, public artwork and the creation of new ticket offices and retail space. It includes DDA enhancements such as hearing loops and tactile maps and paving. To avoid passenger disruption, most of the works were carried out in short
night-time possessions and at weekends.

This set an important precedent; the 11 completed so far (all to time and budget), incorporate bright, modern environments and reduce everyday operating costs through more modern and energy-efficient materials. All of the system’s 28 escalators have been replaced with more energy-efficient versions that also use 98% less lubrication, under a contract with Otis completed in 2015. Design work for the final four stations (St Georges Cross, Cowcaddens, Kinning Park and West Street) has been completed with construction works to begin in late 2018 or early 2019.

“This work was partly about the condition of the assets, but also about how you present yourself to the customer. I remember meeting David [Sidebottom – Passenger Director of Transport Focus, the independent UK passenger transport watchdog] after the results of the last annual passenger survey came out and he pointed out a particular statistic, the difference between a good journey and a great journey. He said he’d never seen stations rated so highly.

“This was credit to the fact that we determined investment in stations was so important, because when you speak to other operators it’s all about trams or trains, signalling, and reliability – which is the fundamental bedrock. But don’t forget about the environment you’re investing in, and what value that brings to the surroundings.

“We had 1970s stations that were pretty grotty, and while they’re still pretty small the 11 completed so far are almost unrecognisable.”

Closures and leaks

Although the intention had been to complete major works without closing the system, this was unavoidable for a six-week period in July/August 2016 for replacement of the depot access tracks. This GBP5m (EUR5.7m) design-and-build contract was completed by Colas Rail and involved renewal of the concrete trackbed and drainage and relaying of the rail, switches, crossings and point motors. In the first planned closure in over 30 years, bus replacement services mimicked the circular service on the surface.

Mr Hoskins describes the works: “The only place that trains cross over is the ramps and turnouts at the depot, so we couldn’t operate trains in that area for that scale of infrastructure renewal. Although taking slightly longer than originally planned, Colas did an excellent job and what we got out of that is infrastructure that’ll see us through the next 40 years.”

While station refurbishment and track replacement have a more tangible direct impact on the passenger experience, other significant tunnel remediation has carried on behind the scenes. The depth of the lines varies considerably, between three and 35m below the surface, due to prevailing geology, and due to this complexity encountered by the original engineers – including negotiating former quarries and abandoned mineshafts – no uniform method of construction was adopted. Consequently some sections are cylindrical while others are a horseshoe shape, with a variety of brick, concrete and cast iron linings. These conditions, in conjunction with changes to the surrounding soils over the last century have led to varying degrees of deterioration and an increase in water ingress.

Following detailed studies, a tunnel lining improvement plan was agreed with Freyssinet in December 2014. A vital component of the modernisation, this included improving the structure and fabric of the tunnels and trackbed in night-time possessions, with strengthening, repairs and caulking to reduce the volume and impacts of water ingress.

As Hoskins explains: “When Freyssinet came in, one of their biggest challenges was in devising a lot of bespoke equipment to reduce manual handling in the tight tunnels to meet the tight deadlines. This project has been recognised with numerous awards, so the lesson is to take the time to get the right partnerships – it’s worth the effort.”

He continues: “With the Subway being at the depth it is at various points and running underneath the Clyde in part, we do have to deal with water ingress so a lot of investment is not just in the tunnel lining but the sumps and pumps that we use as well. So I challenged the team and ourselves to how we could bring innovation to an environment like that.

“The water and the air in the Subway system is at a constant 14-15°C, so working with Glasgow Caledonian University through a Knowledge Transfer Partnership we came up with a plan to use both air and water source heat pumps in the stations, so even in our 122-year-old system you can still find those opportunities.”

Other works required the removal of 120km (75 miles) of redundant cable, and the Subway’s 21 pumping stations have seen replacement equipment as part of a GBP2m (EUR2.3m) contract awarded to WGM Engineering in 2014.

Tailor-made trains

Delivering the UK’s first UTO (Unattended Train Operation) project, when replacing the rolling stock and control systems, SPT undertook a process of describing the desired operational requirements rather than starting with a detailed technical specification. Working with Glasgow-based consultant Racon and SYSTRA, and now Atkins, prospective suppliers were invited to enter into a competitive dialogue to develop solutions delivering the best value for money.

The outcome has seen the procurement split into two contracts – one for manufacture and supply (MSA), and one for technical support, spares and maintenance (TSSSA). This led to two agreements in March 2016 with a joint venture of Ansaldo STS and Stadler; the TSSSA runs for ten years as Mr Hoskins explained: “We don’t necessarily know that supply chain so we need that technical support and we need them to supply the spares”.

Stadler is to supply 17 articulated trains with walk-through gangways and secondary air suspension for additional passenger comfort. At 39.24m long, the new four-car vehicles gain 1.5m in length over the existing three-car trains and will have capacity for 309 passengers, 110 seated and including six tip-up seats, compared to the current 270. They will also accommodate wheelchairs. Maximum operating speed will see a slight increase at 58km/h (36mph) and the AC traction motors will be water-cooled with IGBT traction control for regenerative braking. Sixteen will be required in peak hours, with an additional spare.

Temporary cab partitions will be included for initial passenger service, to be removed after the transition to UTO and creating valuable extra space. In the initial driven months, the Subway will have mixed fleet operation – which Mr Hoskins describes will be an “interesting period”.

Predictive maintenance functionality is being built into the new fleet with critical systems monitored continuously to alert staff to issues before they become failures that require removal from service.

This marks Stadler’s first order for an automatic, driverless system and the trains are being built at the company’s facility at Altenrhein, Switzerland. The first train debuted at the InnoTrans exhibition in Berlin, before its arrival in the Broomloan depot.

Such a design and supply contract was a perfect fit for Stadler, a manufacturer that is relatively new to the UK but which has a fine reputation for specialised rail vehicles for some of Europe’s more unusual rail operations that necessitate lower production runs and quick turnaround times.

The company’s first foray into the UK came in 2011, driven by Transport for London’s tight schedule for increasing capacity on its Tramlink network in readiness for the 2012 Olympic and Paralympic Games being hosted the following year. The first Variobahn was delivered just 145 days after signing of the contract and went into service on 30 March 2012. Subsequent options have taken Tramlink’s roster to 12 Variobahn trams, the latest delivery in October 2016.

Since then the company has seen success with electric and bi-mode heavy rail cars for Abellio Greater Anglia (to enter service next year) and a GBP460m (EUR524m) order for bespoke electric trains for the Merseyrail network. These four-car articulated metro-style EMUs will enter service in 2020 to replace ex-BR stock dating from the 1970s. One train per week will be delivered from the summer of 2019.

In June 2018, an order for Citylink tram-trains and FLIRT multiple units was placed for the future South Wales Metro project; the company delivered similar units to the UK’s tram-train pilot between Sheffield and Rotherham following its acquisition of Vossloh’s Spanish rolling
stock business in late 2015.

Its decision to pursue the Glasgow Subway contract was no doubt bolstered by success in its first commission for underground trains; an unusual project for 2.4m-wide Kleinprofil trains for Berlin’s U1-U4 U-Bahn lines.

Passengers will notice the changes immediately, Hoskins enthuses: “We’ve never had things like TFT screens and passenger help-points, so we’re integrating all that and CCTV as well. One of the big other things is advertising. That’s a significant revenue stream for us, so it was important that we took the advertising company with us in terms of the initial design to maximise those opportunities without affecting the brand in terms of what we’re giving to the customers.”

Each train includes 14 15in (38cm) high-definition screens, with six for advertising and eight for passenger information.

The rolling stock contract forms just under half of the GBP200m (EUR225m) upgrade package, with Ansaldo STS responsible for signalling and depot upgrades.

Control systems and the OCC

Although it currently uses fixed block signalling, the Glasgow Subway solution is slightly different to other underground railways due to the narrow tunnel bores and unique electrification setup.

Conductor rails on the walls supplying train lighting also feed the signalling system so when a train occupies a particular track section the lighting current actuates the signal. The current is interrupted when the section is passed so the ‘line clear’ signal is given. To guard against a train entering a section with extinguished lights, trip cocks are installed at the entrance to each block.

UTO requires fully automated signalling and control, and the Subway is an ideal candidate for conversion being fully segregated, with one depot and no interfaces with any other rail network.

Hoskins explains: “CBTC with UTO will get us down to three-minute headways with 90-second headways possible. We need this as one of the key areas we serve is Ibrox stadium, so it’s about pushing crowds through quicker for events. It also integrates with the platform screen doors [PSDs], a real focus for the ORR [Office of Rail and Road] in terms of safety.”

The chosen system will be the same proven Ansaldo solution supplied to Copenhagen, Milan and Stockholm. Car-borne Controllers (CC) calculate the train’s position using a tachometer which records the distance travelled between track balises and transmits this to the Zone Controller. This determines movement authority, communicating back to the CC to dictate the trains’ speeds, adjusting traction power or braking as required. The system also controls the trains’ doors and other associated systems and manages performance so can direct vehicles to the depot for service as required. Hoskins explains: “The new system minimises wayside equipment and this is very useful given the environment that it is going into.”

Detailed design for the new Operational Control Centre (OCC) was completed earlier this year, with construction underway. Completion is expected in summer 2019.

Development of a 750m test track at Broomloan is also underway, a current focus for the Ansaldo/Stadler joint venture ahead of the delivery of the first train. Due to the unusual gauge, dynamic testing cannot begin until the first vehicles arrive in Glasgow.
An existing segregated track laid during the 1979 modernisation and mothballed for many years is being rehabilitated for this purpose, and a new assembly site and store will be built alongside. This will be fitted for CBTC operation and feature a PSD-fitted platform for staff safety.

In other Broomloan upgrades, a new wheel lathe will remove the need to send wheelsets away for tyre turning and a new UTO-compatible trainwash will be installed.

The final stage of the modernisation will be the installation of the 1.7m station PSDs. Installed by Gilgen Door Systems and controlled by the CBTC system, all new trains need to be in service and the old fleet removed before this can happen.

The challenges of UTO

Although UTO conversions for manually-driven lines are rare, they have been seen before. Nürnberg (Nuremberg) completed the transition for its U2 U-Bahn line in 2010, with line 1 of the Paris Metro opening after major works in July 2012. Further lines in the French capital are to follow suit, with RATP awarding a contract to Siemens to automate line 4 by 2020. SPT is learning from these other operators through close ties as part of its membership of UITP.

Due to the impact of such major works, such UTO transformations only make sense
if carried out to coincide with major fleet or infrastructure renewal programmes;
RATP estimates a return on investment period of around ten years.

Glasgow’s transition from ATO (GoA2) to UTO (GoA4) on a live system is challenging, and understandably requires continuing engagement with SPT’s frontline staff. As Hoskins explains: “This fifth workstream is probably the one I spend most of my time on – our people. It’s about communicating with those staff who are helping us achieve 97% customer satisfaction as they are the ones equally fearful for their jobs when you talk about UTO and driverless. So I spend a lot of time talking to them about what that future looks like, how
secure that is for them. There may not be as many jobs, but there’s still significant
job security.”

This approach is borne out by looking at examples in Paris, where RATP has successfully redeployed many of its former driving staff, for example within the OCC or to handle technical or passenger-related issues at stations.

Security of another kind is also at the forefront of Hoskins’ mind: “We have a keen focus on cyber security as it’s not just about the physical security, and we have ongoing dialogue with the DfT [Department for Transport] on some of these issues.” Further proactive engagement is ongoing with the Scottish Government on this crucial factor that affects transport operators of all kinds.

Where next on the roadmap?

Mr Hoskins concludes by explaining the roadmap to the project’s completion: “The first three trains will be delivered for type testing soon and while this happens we’ll be installing the CBTC system, firstly in the yard and then in the tunnels.

“Once the new OCC is tested and operational we can do the first overnight line tests and while that’s going on we’ll have units 4-17 delivered. They will then go through the same process of offline testing.

“While the line testing for all units is being finalised, well carry out the UTO transition with the CBTC testing and can install the PSDs during the night-time.”

For the latest updates on the Subway modernisation programme, visit


Article originally appeared in TAUT 971 (Nov 2018).