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Seamless interchangeability

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Imagine Britain’s railways in 2040 and what can you see? Would we even call it a railway? When we’ve got autonomous pods to transport us from door to door, what’s the point of a railway? When we’ve superfast broadband everywhere, will any sort of travel be too expensive – a luxury for the planet to afford?

We railway engineers, and our operating colleagues, say the network is capacity-constrained, but anyone looking at the tracks can see they’re mostly empty most of the time…

Great openers for a chat in the pub with your mates – if they’re so inclined. But also serious questions not only for the UK but for the world. The more we grapple with climate change – represented by one of those four Cs that underpin our Railway Technical Strategy (namely Carbon; alongside Capacity, Cost, and of course the Customer).

The RSSB Innovation Programme sought and funded projects to develop ideas for ‘Radical Trains’ in a competition which has now come to fruition. Seamless Interchangeability is one of the fruits borne, quantifying significant benefit from a radical approach, not just to trains, but also to running a railway. New high-speed railways are being progressed, but what could we achieve on the conventional infrastructure – and what more could ultimately be achieved on high-speed lines, maximising overall network utilisation?

Dynamic coupling

Interfleet (now SNC-Lavalin Rail & Transit) and colleagues from Academia posed themselves the question of how to increase capacity further, taking the European Train Control System (ETCS) Level 3 – automatic train control – as a start point. We know closer running is already being considered, but how much more network capacity would we gain from actually joining trains together – coupling up (and uncoupling) – on the move?

For example, a long train composed of individual trainsets or vehicles might depart from a high-density London hub, and split en route with smaller trainsets breaking off from the rear to serve regional stations, whilst the front portion continues non-stop to, say, Edinburgh.

Dynamic coupling would also work in reverse, allowing passengers to travel from a regional station such as Hull, Lincoln or Oakham with their carriages being speeded up ahead, and then joined to the front, of a non-stop train en route.

“There’s no such thing as a new idea” goes the adage and, as those who know their history will assert, the rear- uncoupling process re-invents slip-coaching (but safely – with a controlled, independently-braked train). Front- coupling is, however, without precedent and trickier, but a credible build on ETCS Level 3 – the project’s starting point. ETCS would control trains until the minimum conventional safe separation, then train-to-train communications would supervise at distances smaller than relative braking distances. An alternative (to be designed) system would then switch in to manage the trains down to a maximum closing speed of say five km/h until they couple: conceptually similar to the quasi-static case of coupling two units at a platform.

Instead of changing trains, for journeys to and from regional stations, passengers could walk backwards down the same train. Conceptually, it should be physically easier and psychologically less stressful to walk along a specially designed train corridor to the correct carriage for one’s destination rather than the current process (of having to alight from a train at an intermediate station, find the platform for the next train and board it).

“But, thinking of the UK demographic where half the population will be ‘old’ in 30 years time, what about the elderly and infirm?” asked retired Railway Industry Association technical director Richard Gostling at a Rail Research UK Association (RRUKA) conference. Under Seamless Interchangeability, changing destinations on board the same train should be easier for all passengers – including people who are mobility impaired – than conventional changing at stations. We will certainly need to re-think train interiors and what they’re for – partly for seating, from where passengers can access catering, entertainment and other facilities; and partly as a transfer corridor which passengers use to reach their destination carriage, maybe including a travellator, or something resembling a stairlift, to ride on.

So, Seamless Interchangeability is a radically new operational concept enabling latent capacity to be freed up on the rail network (filling some of that fresh air over the tracks with vehicles), whilst at the same time increasing connectivity and hence customer satisfaction (increasing the number of through journeys to different destinations). Long trains running non-stop would need less energy to stop and start (consuming less carbon) and – in addition to fuel savings – a smaller number of more-efficiently utilised carriages would reduce leasing and maintenance costs.

But would it be worth doing?

Starting not only from the assumption of ETCS Level 3 Automatic train control, but also assuming that it would be technically feasible to design, build and approve suitable rolling stock and safe enough operating principles, what would the benefit of Seamless Interchangeability be?

“We wanted to quantify whether Seamless Interchangeability would make much difference – to establish whether it would even be worth thinking about designing trains and creating new operational rules to deliver the concept,” explained Ian Mylroi, principal consultant at SNC-Lavalin Rail & Transit.

The team persuaded RSSB to fund the research. A software model was built, based on key features of the Midland main line (MML), in Matlab – with Simulink, State-flow and dedicated C-code. The simulation consists of three layers: infrastructure and topology; interlocking safety control; and dynamic train movement.

SNC-Lavalin provided expertise (in human factors, railway control systems and operations, in addition to its business consulting, vehicle and infrastructure engineering teams); as did a specially composed advisory group – including representatives from a train operator (First Group), an infrastructure manager (Network Rail), a train builder (Siemens), and another university (Loughborough).

The combined team came up with parameters for the model, thinking hard about what assumptions were valid to maintain (such as timetabled station dwell) and which were unnecessarily constraining, in order that the true benefits of the Seamless Interchangeability concept could be explored. Sensible simplifications were made, including that individual vehicles had the same traction and braking capability (whether operating independently or coupled together to make a trainset of up to 11 vehicles), as well as the same physical characteristics (23-metre length, 43 tonne unladen mass, 7.5 per cent additional mass due to rotational inertia), and each person weighed 80kg with 10kg luggage.

Similarly, the route model considered representative nominal gradient topology with maximum speeds for each track section based on curvature and junctions, but assumed double-track throughout with four platform tracks at all stations, and ignored power loss over neutral sections.

The model recognises that other technologies will have advanced by 2040, so assumptions are made to ensure that the additional benefits that Seamless Interchangeability would bring are conservatively assessed. For example, regenerative braking is assumed by then to deliver double today’s best of 30 per cent conversion rate from kinetic energy back into traction power. By thus overstating the likely regeneration improvement in 2040, we understate the significant carbon benefit of the Seamless Interchangeability pattern of reduced stopping and starting of long through-trains.

The model provides a baseline against which other scenarios can be tested and developed, using the software’s graphical user interface to vary parameters. It is not a perfect replica of the detailed features and absolute values of current MML operations, but the model is sufficiently realistic that changes in Key Performance Indicators found under the different scenarios tested are real: and they show significant benefits.

What would we gain?

The main target was to enhance network capacity, but the team found that Seamless Interchangeability actually offers improvements on all four Cs of the Rail Technical Strategy.

Simpler journeys with fewer changes would increase customer satisfaction (although this benefit was not quantified); fewer stops for through services – and more efficient vehicle utilisation – would halve the miles run overall, cutting maintenance and traction energy costs and reducing carbon accordingly.

Fewer stops would also enable more efficient use of the network, doubling capacity by creating more paths to run trains and by reducing journey times, further enhancing customer benefits.

Despite the system deploying fewer vehicles than currently, potential disbenefits from doubling passenger loading were not seen: load factors remained below 90 per cent in all scenarios, albeit noting the simplifications made – such as to assume that all rolling stock had exclusively standard class accommodation. A negative consequence of the overall optimisation and aggregate reduction in journey times was that a few journeys would take longer, such as those to small regional stations adjacent to significant hubs which are currently served infrequently, but directly, by intercity-style trains.

Could it be implemented?

Technically, implementation of Seamless Interchangeability on the railway would require a paradigm shift in rail operations and rail travel. Implementation requirements have been developed and worked up to give indicative costing for four key system elements: signalling, vehicles, operations and infrastructure.

Signalling for Seamless Interchangeability is a logical extension of the current cross-industry work towards ETCS implementation and could progress at marginal cost to that massive overall project. Vehicles will need significant modification to trainsets at the front and rear to enable dynamic coupling, and to interiors so as to facilitate passenger transfer to the correct portion of the train. The project concludes that research would be worth initiating, such as to revisit crashworthiness criteria given signalling system robustness and further potential for modal shift onto railways from less safe, less carbon- friendly modes. Interestingly, the biggest changes needed may be to the infrastructure, particularly station layouts which may require significant investment, and possibly more land-take, to deliver the Seamless Interchangeability concept.

So where are we going?

Perhaps, returning to the initial Radical Train idea, people in 30-odd years time will leave their homes in automated driverless pods to travel to stations where they dock into trains which couple dynamically through Seamless Interchangeability into longer trains. Then they’ll move down the train to their destination vehicle and subsequently slip off from the combined running into individual pods again to reach their destination doorstep.

Operational rules would need to be developed to support each stage of implementation, building on a fresh look at overall system safety and how people could best use Britain’s railways. Initial modelling found that, compared to the vehicle and operational challenges, infrastructure and system investment costs were low, readily traded off against reductions in fleet size (and therefore reduced vehicle leasing and maintenance costs), and lower traction power costs. Refining these cost estimates is a key area for future work.

The world moves on. Since the Seamless Interchangeability project described here was conceived, RSSB has developed a project known as Closer Running under the cross-industry FuTRO (Future Traffic Regulation Optimisation) Board. FuTRO aims to identify technologies to support a vision of the rail industry in 2040: technologies which optimise traffic management, increase network capacity, reduce energy consumption, hasten service disruption recovery, and improve customer communications and satisfaction. Seamless Interchangeability logically meshes with FuTRO’s closer- running research programme going forward.

Seamless Interchangeability is no quick fix to rail capacity, but the project has established that it’s worth pursuing. Proposed next steps are to focus on a particular route to consolidate understanding of the benefits – and costs – of adopting the novel approach, prior to devising a network-wide implementation plan.

Clive Burrows, group engineering director of First Group and chair of the FuTRO Board, said: “You have uncovered the results we hoped for, and a lot more besides. The question is how best to address the challenges to Seamless Interchangeability so we can begin to design and evolve the technologies and the thinking to deliver an optimal future railway.”

Written by Rebeka Selick, who was formerly head of research at SNC- Lavalin Rail & Transit and is now head of rail at TRL. Thanks to SNC-Lavalin Rail & Transit, RSSB, Siemens, Network Rail, First Group and Loughborough University for their help in preparing this article.


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