Train-centric signalling

Could avionics and satellite technology hold the key to the future of main line signalling? Aerospace technology is not usually something associated with railways. But that could be about to change. The next generation of main line signalling technology – ETCS Level 3 – will draw on know-how from outside the traditional rail sector to deliver a step change in safety, capacity and reliability.

Paving the way

First put forward more than 25 years ago, ETCS (the European Train Control System) is designed to promote cross-border mobility for rail traffic by providing a single interoperable signalling system.

There are three ETCS levels. Currently, ETCS Levels 1 and 2 are widely used throughout Europe. ETCS Level 1, the baseline version, provides train protection and speed supervision. With ETCS Level 2, continuous track-to-train radio communication makes it possible to eliminate lineside signals and increase performance.

Migration to ETCS Level 3 is the next step. This represents a major departure from traditional signalling practice. Instead of using trackside infrastructure to determine the position of trains – the foundation of signalling for more than a century – ETCS Level 3 specifies that trains localise themselves.  

“It completes the journey from track-centric to train-centric signalling,” says Klaus Mindel, Head of Product Management for Train Control, Thales. “Positioning and integrity supervision are all carried out on-board the train.”

ETCS Level 3 is important for several reasons. One is that it reduces infrastructure costs because trackside train detection is no longer needed. Another is that it boosts capacity: ETCS Level 3 is a ‘moving block’ technology with separation between trains governed by speed and distance, rather than fixed geographical blocks.

It also paves the way for greater automation. “This is important given the rapid rise of driverless technologies for cars and lorries,” notes Mindel. “If rail is to build a competitive edge over road, it will need to follow a similar route.”
Bringing Level 3 to life

Thales is committed to developing an ETCS Level 3 solution and the company is actively involved in the development of the standard. It is also fine tuning the technologies needed to turn ETCS Level 3 into a reality.
 
“We have an on-board system in development that is ETCS Level 3 ready,” confirms Mindel. “Going towards train-centric on-board systems is a critical element in the whole system design.”

Thales has led the deployment of ETCS right from the start. The company delivered the world’s first commercial ETCS Level 1 project back in 1999. It also delivered the first cross-border ETCS implementation. Today, Thales’ ETCS Level 2 solutions are deployed in some of the world’s biggest and most prestigious rail projects, including Switzerland’s Lötschberg and Gotthard tunnels.
Building blocks

Thales’ success in delivering complex ETCS projects is underpinned by its mastery of main line signalling technologies. Among these are radio communications, electronic interlocking and on-board systems for the trains themselves.

Experience from the urban rail arena is equally important. ETCS Level 3 will be the first major main line signalling system to use moving block. Thales is an expert in both moving block and Automatic Train Operation (ATO). The company perfected these capabilities through communications-based train control (CBTC), a technology invented by Thales more than 30 years ago.

    We are uniquely positioned to bring forward a system that will work. It’s not only our long history and experience in rail signalling, but also our expertise in fields such as satellite positioning, avionics and inertial positioning.

“We are uniquely positioned to bring forward a system that will work,” says Kai Taylor, Marketing Director Main Line Signalling, Thales. “It’s not only our long history and experience in rail signalling, but also our expertise in fields such as satellite positioning, avionics and inertial positioning.”

Overcoming obstacles

Delivering ETCS Level 3 demands engineering skills beyond the realm of conventional main line signalling. One of these is being able to pinpoint trains as they move around the network – without the help of trackside systems.

While satellite positioning can be used for this purpose, problems arise when trains enter tunnels. Odometers, which measure the distance travelled by train wheels, cannot be relied on because wheels often slip on wet rails, particularly when trains leave tunnels.   

To solve this problem, Thales’ signalling experts are using sensor fusion to combine positioning data from a range of inputs. They’re also tapping into the expertise of the wider group, including the company’s space and avionics divisions.

    Would we be able to take an inertial positioning system from an aircraft and put it on a train?  We already do it for land vehicles, so the answers is, yes, we could.

“Would we be able to take an inertial positioning system from an aircraft and put it on a train?” asks Taylor. “We already do it for land vehicles, so the answers is, yes, we could. We’re using our corporate DNA and knowledge from our research activities to provide customers with the best solutions.”

ETCS Level 3 is a game changer. As well as boosting capacity and performance, it reduces life cycle costs because there’s less trackside equipment to maintain. And because it’s radio-based, using either GSM-R or high-capacity LTE, it offers high levels of reliability. There is also scope for energy savings and better traffic management.

“Our strategy is to deliver all of these benefits as a standardised, interoperable solution,” says Mindel. “ETCS Level 3 is on our agenda and the knowledge we have means we can offer our customers a clear migration path.”