Signalling systems are essential to ensure safe train operations, but they are also key to enable optimal capacity use on railway lines. Almost half a century ago, much hope was placed on the then brand-new ETCS system, but modern technologies have developed fast. They might allow for higher transport volumes and faster implementation at a fraction of the cost. Are there better alternatives to the expensive and complex ETCS?
About the Author
Reinhard Christeller (79) is a mechanical engineer graduated at ETH Zürich and an Executive MBA of HSG St. Gallen. Having worked as an engineer and project manager for rack railways in Switzerland and luxury trains in Saudi Arabia, among others, he has held technical, marketing and sales management positions at Schindler Waggon AG, ADtranz in Switzerland and Alstom Transport in France.
He has served on European committees in the railway industry and urban transport sectors. He is currently a consultant in the railway sector, author and editor of railway publications, teacher and translator and concentrates mainly on issues of rail freight and public transport.
Christeller welcomes your opinion on the matter of signalling and ETCS. How can Europe best use these technologies to eliminate rail freight bottlenecks?
Mainline railways were historically – and many still are – controlled by a wide range of national signalling systems. In the mid 1990s, when cross-border locomotives and multiple units were introduced, the need arose for a unified European signalling and communications system to replace the old ones.
This took the name of European Train Control System (ETCS) and was enhanced by GSM-R communications technology to become the European Rail Traffic Management System (ERTMS), maintaining the same block system philosophy in which trains are separated by fixed blocks with lengths that are at least as long as the braking distance of trains running on the line.
This leads to intervals between trains that are longer than the necessary safe distance between them, which is determined by the braking distance between the moving end of the 1st train and the front of the 2nd plus a safety margin.
This is called “moving block” or “ETCS Level 3” and has been discussed for decades, but there is no concrete implementation in view for the next years or even decades. It is needed above all on densely trafficked lines such as major parts of the Scandinavian – Mediterranean and the North Sea – Rhine – Mediterranean TEN-T corridors and specific bottlenecks around Lyon, Île-de-France and the Baltic capitals. Awaiting infrastructure upgrades, a special focus should therefore be placed on increasing capacity at the bottlenecks.
Much has changed since the eighties
Since ETCS development, IT has rapidly advanced. Processor speeds are ~10,000x faster, and mobile data transmission went from 0.2 to 10,000 Mbit/s. While slow, unreliable data transmission doomed 1980s remote brake monitoring attempts, this is no longer an issue. Despite this, rail infrastructure managers plan to spend decades implementing the expensive and already dated ETCS across Europe, with full rollout anticipated a century after its initial introduction.
Implementing ETCS could be a suboptimal solution. New and more advanced signalling systems are available. Some rely on fixed signalling installations and some do not require them. Examples include the German Aerospace Centre’s (DLR) TrainCAS, a decade-old train-to-train communication system operating successfully on the Harzer Schmalspurbahn with potential for SIL4 upgrade even in dense fog at high speed.
The French Urbanloop, developed by University of Lorraine students, is a small, AI-assisted urban transport facility using pods that follow each other closely, localised by passive lineside beacons, and has been operating in Paris.
Ecotrain, also in France, is developing a solution for driverless trains on secondary lines to exchange data with level crossings to prevent collisions. Given that modern cars have sophisticated control systems for collision avoidance and autonomous driving (see the image above), it is unclear why simple ETCS train equipment costs hundreds of thousands of euros, when a complete Urbanloop pod or a high-tech car costs only a few thousand. See the price comparison in the graph:
To maximise railway capacity (after prioritising safety, switch control, timetable adherence, and energy efficiency), the signalling system is crucial. It must accurately track the position, direction, and speed of every train within its area. This essential information enables the safe organisation and optimisation of all train operations.
📌 Possibilities for Train Localisation and Safe Operation (click to expand)
A number of possibilities for the determination of the location and provision of safe operation of a train have been used or can be used. All have their own drawbacks when it comes to precise and at the same time reliable positioning.
- Track circuits for positioning and train integrity supervision.
- Axle counters for positioning and train integrity supervision.
- Fixed electric contact shoes for triggering braking.
- Electromagnetic solenoids for triggering braking.
- Continuous lineside data transmission antennae for positioning and speed control.
- Discrete lineside balises for positioning and speed control.
- Discrete passive lineside tags for positioning.
- Radio connection for speed control.
- Satellite-based positioning (GPS, Galileo, Starlink).
- Wheel revolution supervision for positioning and speed and acceleration/deceleration measurements.
- Odometry for positioning and speed and acceleration/deceleration measurements.
- Local earth magnetic field variations.
As there is now a sufficient number of different independent localisation methods available – each with varying technologies, safety certifications (up to SIL4), availability, and reliability – moving block operation (where trains dynamically adjust their spacing based on real-time data) becomes feasible. This is where we can start to think about alternatives to ETCS.
An idea for a better alternative to ETCS
A proposed signalling system should rely on three of these three localisation methods. Normal operation of trains at maximum speed and minimum headway shall be allowed if all three systems produce matching information. Trains will still be able to operate when two systems agree but the third differs. Speed and headway will then be set to values that depend on which systems are in line with each other.
If all three systems give diverging information, trains will not be allowed to run except at low-speed emergency level (typically “on sight”, probably with a maximum speed of 30-40 km/h) through secured human authority procedures.
Railways are systems and the interaction between their subsystems must be managed. It is therefore also imperative to talk about the detection of train completeness, i.e. loss of wagons. These must be secured by on-train equipment depending on the type of train.
For trains coupled with standard “screw” couplings, it is a fact that today no solution for SIL4 train integrity detection exists for serial operation even if several demonstrations have already proven some kind of feasibility. Therefore, a certain level of redesign of freight trains (and adaptations to passenger trains) will be needed, likely by equipping freight trains with electric power and digitalising them.
It is possible to quite quickly introduce such a modern highly responsive IT-based system to allow train operation under moving block conditions and thus increase line capacity, mainly for freight trains. This could allow a drastic cost reduction for signalling systems.
It could eliminate the need for many of the expensive lineside elements and their cabling, such as track circuits and axle-counters, beacons (balises) that require frequent inspection and maintenance and that are prone to meteorologic impacts and vandalism.
It will also lead to a reduction in the number of interlockings and control centres. In combination with other improvements in infrastructure, terminals and rolling stock design, it will entail a substantial boost at a fraction of the cost of ETCS. It must be designed in such a way as to allow a gradual introduction in mixed operation with ETCS or another legacy system. As long as other trains operate nearby under a traditional signalling in mixed operation, trains that are equipped with the new system must run according to the rules of that system.
Years, not decades
Modern trainborne IT technologies, which require no extensive fixed infrastructure, can be implemented as an overlay and eventual replacement for legacy signalling systems. This approach facilitates a rapid transition to moving block operation on critical bottlenecks. As a result, significant improvements and cost reductions for freight lines can be realised within years, rather than decades.
To ensure an effective improvement of rail transport, political support is mandatory. Politicians should not only suggest but also finance the ideas and transform them into legal instruments. The railway sector at all hierarchy levels should take benefit from new developments in the aerospace and automobile industries. But the full impact on capacity will only materialise if synergies with parallel improvements in logistics, infrastructure design and maintenance, energy supply and freight train design are integrated.
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