London’s Crossrail project might hold the prestige with its dramatic images of sub"> London’s Crossrail project might hold the prestige with its dramatic images of sub"> London’s Crossrail project might hold the prestige with its dramatic images of sub">

Thameslink signalling

Thameslink signalling
22 June 2015

London’s Crossrail project might hold the prestige — with its dramatic images of subterranean tunnels and floating stations in Canary Wharf docks — but it is just part of the transformation of the capital’s commuter network in progress.

Promising to do for north-south travel what Crossrail will bring to east-west, is Thameslink, a £6bn, nine year programme of works also due to complete in 2018. Stretching from the south coast of England, through London’s suburbs and central districts, and as far north as Kings Lynn by the Norfolk coast, Thameslink will bring new, longer trains, resolve some notorious network bottlenecks, and deliver major improvements to key stations, such as Farringdon, Blackfriars and London Bridge, amongst others.

As more of an upgrade of existing infrastructure (some tunnel sections date back to the 1860s) than a new build, Thameslink’s transformation is a gradual, incremental process. Yet it has already begun to deliver results, with the central London section already unrecognizable from just a few years ago.

Signalling in the Thameslink ‘Core’

Central to the entire programme is the ‘Core’ — a short, double-track section between Blackfriars and St Pancras through which all cross-city services will pass. With a new signalling design to cater for up to 24 trains per hour (current capacity is 16tph) this section will offer service frequencies more akin to that of a metro. And herein lies a major technical challenge for Thameslink, and it is where a team from Ricardo Rail (formerly Lloyd’s Register Rail) is busily engaged.

Most metro systems under construction or refurbishment today would turn to Communications Based Train Control (CBTC) to manage the level of traffic intended for the Core (as, indeed, Crossrail will for its own central section). This is because CBTC is designed for the stop-start nature of metros, with automated control of train movements allowing shorter headways between services.

But as a Network Rail project — and consistent with their commitment to adopt train control technology championed by the EU to bring consistency across Member States — Thameslink will use the European Train Control System (ETCS) as its standard for signalling. This is despite preconceptions that ETCS is optimized for regional and national mainline railways and not a metro-style operation.

However, Thameslink has developed the concept of an ETCS railway overlaid on a conventional signalling system to deliver a ‘metro style’ operation. The high capacity is achieved through two new features:

  • ETCS allowing the implementation of shorter block sections in a conventionally signalled area, in particular around stations
  • The first use of an Automatic Train Operation (ATO) with ETCS on the mainline railway, to allow consistent train driving

Furthermore, by retaining the conventional signalling, a fall back system will be present in the event of ETCS failure.

David Mee, Principal Consultant, has been an integral part of the project team since the signalling concept was first in development in 2009.

“2015 is a key year”, he says. “After months of development for the concept for delivering 24 trains per hour through the core, we will start the test runs at ETCS National Integration Facility near Hertford this spring, before proceeding to night time test running in the core itself by this autumn. So, we are moving towards a significant point of the whole programme”.

For David and his team within Network Rail, this will be the culmination of many months’ work and planning.

“Our role has been to develop the safety programme for the project. Being involved from an early stage allowed us to influence the subsystem requirements and operations, not only to achieve high levels of safety but also to ensure performance is optimized.

“We started in 2009 with the high-level operational requirements and developed application scenarios to model in detail how the new ETCS would work, at the same time looking at every possible risk to the system’s safe and efficient operation”, says David. “Since then we have moved onto looking at the integration aspects of the chosen signalling technology, using the scenario modelling to identify the detailed subsystem functional and safety requirements, and develop new operating rules and principles".

‘Vital that we get this right’

David states: “By using ATO, with the underlying Automatic Train Protection (ATP) provided by ETCS, the core section will safely support trains passing at 2.5min headways, and enable service recovery mode with headways of just two minutes, when necessary. However, the technology must first undergo an extensive period of testing.

“This is the first time ATO will be used with ETCS, or indeed on any mainline in this country, so there has been a lot of work to reach this stage. It is vital that we get this right.

“There are a lot of system integration aspects to consider, such as with the new rolling stock that will be introduced from 2016. So whilst we will commence technology testing with a Class 313 test train in March, we will not get to test with the Class 700, the train being built for Thameslink, until next year.”

This means that the switch to ATO will not take place until late 2017 at the earliest. However, it will be in place for the programme’s completion in 2018, which is when the five-year rebuild of London Bridge also comes to a close.

Stealthily improving London’s transport

Perhaps the biggest challenge of all for Thameslink’s managers has been keeping the network — including the core, and its major stations — operational throughout.

It has occasionally proven to be a thankless task that has, at times, asked a lot of its passengers. Yet Thameslink has stealthily improved London’s transport offer already. Blackfriars station, which spans the Thames, has won acclaim for its architectural splendour.

More prosaically, the resignalling around London Bridge — including a new dive-under just outside the station — has resolved a major service conflict headache for Network Rail. The resignalling of the Core will be another benefit to add to the list. Less noticeable than the refurbished platforms and modernized trains that will carry passengers through, it will be no less critical to the success of the entire project.