ERTMS : the european rail traffic management system

ERTMS (European Rail Traffic Management System) is the European train traffic management system, consisting of interoperable systems allowing for train protection, automatic train control, and ground-to-train radio communication. ERTMS is the cornerstone of a more integrated European railway system, making it more attractive for passengers and freight transport. Let’s explore ERTMS, its history, and its components.

Summary

With the various technical systems installed in Europe since the 1970s, the European railway area has become highly fragmented, making border crossings difficult. Multi-system trains, such as the red Eurostar, present very high complexity, resulting in higher operating costs.

Thus, a first component of the ERTMS system was specified in the 1990s: the European Train Control System (ETCS). It is supposed to replace all national systems in the coming years. The GSM-R radio system, also a component of ERTMS, was specified in parallel with ETCS. It supports communication between the train and the trackside. Based on 2G, GSM-R is becoming obsolete and will be replaced by its successor: the Future Railway Mobile Communication System (FRMCS).

The automatic train operation option, ERTMS/ATO, was standardized in 2023, after several years of specification, development, and testing work. This functionality, which has existed for many years in the metro world, makes the deployment of ERTMS/ETCS more attractive and paves the way for mass transit on the national rail network. Cities like Hamburg and Stuttgart are adopting the duo ERTMS/ETCS + ERTMS/ATO to increase the frequency of their commuter trains, thus maximizing the intensity of use of existing infrastructure.

The ERTMS system will continue to evolve. Indeed, operational and technical harmonization efforts continue within the Europe’s Rail project. Thus, new control-command and signaling components will be integrated into ERTMS to further move towards a single European railway area.

Last revision : 18/02/2024.

Content

• Introduction
  • Railway grades of automation
  • GoA1 : supervised driving
• The ERTMS system
  • Purpose of ERTMS
  • ERTMS components
  • ERTMS benefits
  • ERTMS Game Changers
  • Governance
• ERTMS/ETCS : the european train control system
• ERTMS/ATO : towards the autonomous train
• ERTMS : from ATP to an integrated CCS system
• Synthesis

1. Introduction

1.1 Railway Grades of Automation

Rail signaling and automation technologies offer different levels of train operation automation. A definition proposed by the UITP (International Association of Public Transport) is the Grade of Automation (GoA), ranging from 0 to 4.

• GoA0: Manual operation,
  • In manual operation, the driver accelerates and brakes the train based on what they see in the environment (signals, obstacles, hazards). No device is there to supervise their driving. Manual operation is commonly used for tramways, where speeds remain low.
• GoA1: Supervised operation by a protection system,
  • GoA1 provides a first level of automation, as the operation is supervised by an Automatic Train Protection (ATP) system.
  • An ATP can protect the train against passing closed signals or exceeding a speed limit by automatically applying emergency braking.
• GoA2: Automated traction and braking,
  • In this level, an autopilot generates traction and braking commands and sends them to the train instead of the driver: this is the Automatic Train Operation (ATO).
  • The ATO generates these commands based on the signaling limits provided by the ATP, while respecting the mission schedules to be carried out. The ATP continues its supervision and automatically applies emergency braking if the ATO does not comply with the signaling.
  • The driver remains in the cab and continues to observe the environment to take over in case of degraded situations.
• GoA3: Autonomous train, with onboard personnel,
  • In GoA3, there is no longer a driver in the cab. Environmental hazards (obstacles, dangers) must be supervised by other means.
  • Personnel remains on board to advise passengers and intervene in case of contingencies.
• GoA4: Autonomous train, without onboard personnel,
  • This is the most advanced level of automation, in which there is no onboard personnel.
  • This is the degree of automation of driverless metro systems.

1.2 GoA1 : supervised driving

1.2.1 The need : to protect the trains

According to French railway safety agency EPSF [1], following dangers exist in railway operations:

• Derailment: an incident or accident in which a railway vehicle leaves the rails, either fully or partially, with various possible causes (equipment or infrastructure failure, excessive speed, etc.);
• Head-on collision: a frontal collision between two trains;
• Rear-end collision: a collision from behind when a train hits another train in front of it;
• Side swipe: a lateral collision between two trains that occurs at an intersection or junction of tracks;
• Collision with an obstacle (rockfall on the track, a road vehicle present at a level crossing, etc.).

To mitigate some of these hazards, railway operators have implemented solutions. For example, signals along the tracks that the driver must adhere to. However, this is not always sufficient.

In GoA0, i.e., in manual operation, the driver’s vigilance is not always assured. This is why automation systems have been developed to supervise the movement of the train : this marks the beginning of GoA1.

1.2.2 The introduction of automated systems

Operators have implemented first protection systems, such as the “crocodile” in France, invented in 1872. [2]

The crocodile is a device installed at the foot of each signal. It alerts the driver with an audible alarm in the cabin when passing a signal displaying a restrictive aspect. The driver then has a few seconds to acknowledge the information by pressing a button. In the absence of acknowledgment within the specified time, the train automatically stops.

The German PZB system, whose first version was developed in the 1930s, equipped 32,398 km of the federal network in 2019. [3]

This device has three functions: applying braking when crossing closed signals, monitoring non-exceedance of a maximum speed on a section of track, and monitoring the driver’s acknowledgment of crossing warning signals. The PZB is part of train protection systems: the ATPs.

In France, the crocodile is not sufficient to prevent railway accidents. During the 1980s, SNCF decided to equip its trains with an ATP: the KVB. The Contrôle de Vitesse par Balises (KVB) is a mandatory equipment on a train, allowing it to operate on the French network.

Onboard computing unit UEVAL (Unité d’EVALuation) of French ATP KVB.

Credit : Bastian SIMONI

1.2.3 National ATPs and the interoperability issue

France equipped itself with its protection system, the KVB, in the 1980s. Other countries in the European Union turned to their national industries to equip themselves with systems for train protection. Some systems also allow for the display of signaling information in the cabin.

Indeed, the construction of high-speed lines has brought about a challenge: the driver can no longer perceive signals along the tracks at high speeds. A system displaying signaling information in the cabin is therefore necessary. Consequently, operators turned to their national manufacturers to design these systems. This has led to a wide variety of signaling systems within the Union, making interoperability difficult and costly.

The red Eurostar, the high-speed train between Paris-Cologne-Amsterdam, is an emblematic example of the challenge posed by the multiple protection systems in Europe. In order to operate in France, Belgium, the Netherlands, and Germany, this train is equipped with 7 different onboard ATPs [4]

• France: crocodile, KVB, TVM
• Germany: PZB, LZB
• Belgium: TBL
• Netherlands: ATB

Credit : Eurostar

1.2.4 An heterogenous european railway system

All these protection systems consume space inside the train (computer cabinets, sensors, and undercarriage antennas). Their integration is a very complex and costly task. Additionally, the driver must be trained in the use of all these systems, making their job more complex. Finally, maintaining a train with all these systems over time represents a significant cost.

These various complex protection systems greatly complicate the interoperability of the European railway system. Consequently, the idea of replacing these systems with a single protection and cabin signaling system in Europe emerged in the late 1980s. [5]

Source

1.2.5 Towards the genesis of a harmonized technical system in Europe: ERTMS

It was with the EC Directive 1996 on the interoperability of the high-speed railway network that the concept of an interoperable signaling control system, as well as the characteristics of ERTMS, were introduced. [5]

Signaling industry manufacturers, grouped under a structure called UNISIG, produced the first technical specifications of ERTMS in 2000.

In 2002, the European Commission introduced ERTMS specifications into the Technical Specification for Interoperability – Control-Command and Signaling for the trans-European high-speed railway network (Commission Decision 2002/731/EC). Since then, the installation of ERTMS has become mandatory on new high-speed lines falling under the trans-European network.

In 2006, the first Technical Specifications for Interoperability concerning the trans-European conventional railway network were published by the Commission (Commission Decision 2006/679/EC).

Finally, in 2012, the Technical Specifications for Interoperability of Control-Command Signaling were merged to cover both the high-speed and conventional networks (Commission Decision 2012/88/EU). [5]

To date, national ATPs are obsolete. They are referred to as legacy systems or class B systems in the European Union nomenclature. Class B systems must be replaced by the ERTMS/ETCS ATP.

2. The ERTMS system

2.1 The purpose of ERTMS

The purpose of ERTMS is to be the technical cornerstone of the future single European railway area. ERTMS notably addresses the interoperability point of the transport policy. ERTMS will gradually replace the plethora of national systems, thus contributing to interoperability.

During the creation of the ERTMS system, attention was focused on replacing national ATPs and ground-to-train communication. This resulted in the creation of the first two components: ETCS and GSM-R. Automatic Train Operation (ATO) in the presence of a driver was integrated into the ERTMS system in 2023.

Credit : ertms.net

2.2 ERTMS components

In 2023, ERTMS consists of three elements:

• ETCS: European Train Control System. This is a train protection (ATP) and cabin signaling system, which is intended to eventually replace all national ATP systems of EU member countries.
• GSM-R: Global System for Mobile communications – Railway. This is a radio communication system, based on 2G, to provide voice and data communication services between the train and the trackside. Since GSM-R is based on 2G, an outdated technology, it will be replaced by its successor, FRMCS, by 2030.
• ATO: Automatic Train Operation. This is an autopilot system that allows for automatic traction and braking of the train in the presence of a driver.

2.3 ERTMS benefits

According to the European Commission, ERTMS offers several advantages compared to class B systems. [11]

• Enhanced safety: ERTMS/ETCS ATP provides a higher level of safety compared to class B systems.
• Increased capacity: ERTMS/ETCS ATP allows for increased line capacity by minimizing the distance between trains. It should be noted that the benefit also depends on the characteristics of the track and the signaling systems existing before the implementation of ERTMS/ETCS.
• Improved performance: ERTMS/ETCS specifications demand a high level of performance for components, leading to increased availability, which improves punctuality.
• Maintenance cost reduction: With fewer trackside equipment in ERTMS/ETCS level 2, through the elimination of side signals, and the elimination of trackside train detection.
• Personnel: More and more railway companies are facing challenges in renewing their retiring staff. The deployment of ERTMS, combined with the deployment of digital interlockings and Automatic Train Operation (ATO), allows for increased operational productivity.

2.4 ERTMS Game Changers

The ERTMS Game Changers were introduced with the 2023 revision of the Technical Specification for Interoperability – Control-Command and Signaling. They are key to the future digitization of the railway system and aim to provide increased capacity and better performance. [12]

1. Automatic Train Operation (ATO) in GoA1 and GoA2 automation levels, aimed at reducing train energy consumption and increasing capacity.
2. Preparation for FRMCS, which introduces 5G technologies and will eventually replace GSM-R.
3. Optimization of braking curve models to find a better balance between safety and capacity requirements.
4. Preparations allowing the deployment of ERTMS/ETCS level 2 without trackside train detection, supporting moving block. This allows for a reduction in trackside equipment, hence maintenance costs, while drastically increasing line capacity.
5. Onboard management of train integrity, a requirement for implementing ERTMS/ETCS level 2 without trackside train detection.
6. Improvements in the safety and performance of maneuvers by replacing the ERTMS/ETCS Shunting (SH) mode with the Supervised Manoeuvre (SM) mode.

2.5 Governance

2.5.1 European Railway Agency (ERA)

ERA has been founded in 2004 and is an Agency of the European Union. Its role is to define the technical and juridical frame to result into a Single European Railway Area (SERA). The Agency works for a harmonized approach to railway safety by supporting ERTMS. [9] Henceforth, ERA acts as a System Authority for ERTMS.

2.5.2 UNISIG

UNISIG is a consortium regrouping some railway signalling suppliers. It has been founded in 1998, to start writing the ERTMS/ETCS specifications. In 2023, UNISIG’s mission is to develop, maintain and update the ERTMS/ETCS specifications with the European Railway Agency (ERA).

It’s members are : ALSTOM, AZD Praha, CAF, Hitachi Rail, MERMEC, Siemens, Thales, Progress Rail Signalling and MERMEC STE. [7]

2.5.3 ERTMS Users Group

The ERTMS users group is an association regrouping infrastructure managers and railway undertakings that make important investments into ERTMS/ETCS (> 250 million EUR).

The association proposes a discussion platform between the ERTMS users, to provide feedback and return of experience. It also enables the users to align their point of view and consolidates their proposals, for discussion with UNISIG and ERA. [8]

3. ERTMS/ETCS : the european train control system

3.1 Principles

The starting point is the Movement Authority : the permission for a train to run at a given speed and up to a given point of the track (End of Authority).

In the first days of the railways, the Movement Authority was a hand signal given by a trackside personnel, then by mechanical and light signals implemented along the tracks. Some class B systems dedicated to high-speed like TVM (France) or LZB (Germany) display the Movement Authority directly in the cabin of the driver. This is CAB-Signalling.

The objective of ERTMS/ETCS is to transmit the Movement Authority from the trackside to the onboard, so that it can be displayed to the driver via a dedicated screen. The onboard controls that the actions of the driver are compatible with the provided Movement Authority. An autopilot can also be used, this is ATO over ETCS.

To realize its functions, ERTMS/ETCS is composed of trackside and onboard subsystems.

3.1.1 On-board subsystem

The onboard contains all elements necessary to :

• display the Movement Authority to the driver,
• apply the emergency braking in case of overspeed,
• apply the emergency braking in case of overshoot of the End of Authority,
• train positioning on the track plan.

The onboard subsystems rely on a safety computer: the European Vital Computer (EVC), and peripherals:

• the display in the cabin: Driver Machine Interface (DMI),
• antennas to fetch the signalling information from the trackside,
• the odometer, to determine the position of the train on the track plan.

3.1.2 Trackside subsystem

The trackside subsystem is composed of all elements necessary to elaborate the Movement Authority, and to transmit it to the onboard.

The fundamental elements are the following:

• Lineside Electronic Units (LEU), coders that retrieve the signalling information from the lineside signal or the interlocking, convert it into ERTMS/ETCS compliant information, and transmit it to Eurobalises,
• Eurobalises, that transmit the ERTMS/ETCS compliant information (fixed or switchable via LEU) at the passing of the train,
• Radio Block Centre (RBC), that retrieves the signalling information from the interlocking, converts it into ERTMS/ETCS compliant information, and transmits via radio to the onboard units.

4. ERTMS/ATO : towards the autonomous train

The autonomous train is subject to specifications, development, and testing. It is among the key elements for increasing the capacity and flexibility of the railway system.

The autonomous train will be an integral part of the ERTMS system by reusing the ERTMS/ETCS and ERTMS/ATO components, which will be updated to support the maximum level of automation: GoA4.

4.1 ERTMS/ATO GoA2

During the design of ERTMS/ETCS, there was no provision for integrating an autopilot system to automatically manage train traction and braking in the presence of a driver (GoA2).

It wasn’t until the 2010s that operators and manufacturers came together to conceive and specify the option of automatic driving under ETCS: ATO over ETCS.

This system aims to manage train traction and braking while:

1. Adhering to ERTMS/ETCS signaling,
2. Adhering to the timetable received from the traffic management system,
3. Optimizing energy consumption and passenger comfort.

Since its integration into the 2023 revision of the Technical Specifications for Interoperability – Control-Command and Signaling, the ATO over ETCS solution has fully joined the ERTMS system and has become ERTMS/ATO. ERTMS/ATO is already in commercial use, such as on the Hamburg S-Bahn. [6]

Credit : SIEMENS

4.2 ERTMS/ATO GoA4

The next step for the ERTMS/ATO system is to transition from GoA2 autonomy level to GoA3 and GoA4. Specification work began in 2019 within the Shift2Rail X2RAIL-4 project and concluded in December 2023 with the publication of an initial document. Specification, prototyping, and demonstration work now continue within the R2DATO project.

The transition from GoA2 to GoA3/4 raises complex issues: environmental perception, hazard detection, decision-making based on hazards. New technologies are required:

• Computer vision,
• Satellite-assisted absolute localization and inertial navigation,
• Automated decision-making.

These new systems fall within the scope of ERTMS. They are the subject of specification, prototyping, and testing in national and European projects like R2DATO.

Experience feedback and technical feasibility demonstrations will inform the work of the System Pillar of the Europe’s Rail project, whose mandate is to bring specifications to European standards.

Modified locomotive for GoA4 trials in the Train de Fret Autonome project.

Credit : Benoît ABISSET.

5. ERTMS : from ATP to an integrated Control-Command and Signaling system

We have seen that with the emergence of automation allowing train protection and cabin signaling, interoperability became more challenging. Indeed, these systems were all developed differently in each national railway network, making operating a train on the European network quite a feat.

So far, particular attention has been paid to the implementation of ERTMS at the European level to harmonize the ATP function and ground/train communication. While the deployment of ERTMS was very slow initially, there are now ambitious plans within the EU to install ERTMS in the coming years.

However, ERTMS still falls short of covering all systems related to Control-Command Signaling (CCS). The harmonization and integration of these systems within ERTMS must continue in order to move towards a fully harmonized CCS system operationally and technically.

Synthesis

With the various technical systems installed in Europe since the 1970s, the European railway area has become highly fragmented, making border crossings difficult. Multi-system trains, such as the red Eurostar, present very high complexity, resulting in higher operating costs.

Thus, a first component of the ERTMS system was specified in the 1990s: the European Train Control System (ETCS). It is supposed to replace all national systems in the coming years. The GSM-R radio system, also a component of ERTMS, was specified in parallel with ETCS. It supports communication between the train and the trackside. Based on 2G, GSM-R is becoming obsolete and will be replaced by its successor: the Future Railway Mobile Communication System (FRMCS).

The automatic train operation option, ERTMS/ATO, was standardized in 2023, after several years of specification, development, and testing work. This functionality, which has existed for many years in the metro world, makes the deployment of ERTMS/ETCS more attractive and paves the way for mass transit on the national rail network. Cities like Hamburg and Stuttgart are adopting the duo ERTMS/ETCS + ERTMS/ATO to increase the frequency of their commuter trains, thus maximizing the intensity of use of existing infrastructure. [10]

The ERTMS system will continue to evolve. Indeed, operational and technical harmonization efforts continue within the Europe’s Rail project. Thus, new control-command and signaling components will be integrated into ERTMS to further move towards a single European railway area.

Cover picture credit : Ville Rail et Transport

References :

[1] https://securite-ferroviaire.fr/la-securite-ferroviaire/comprendre-la-securite-ferroviaire

[2] https://fr.wikipedia.org/wiki/Crocodile_(signalisation_ferroviaire)

[3] https://fr.wikipedia.org/wiki/Punktf%C3%B6rmige_Zugbeeinflussung

[4] https://www.ertms.net/wp-content/uploads/2021/06/9.-A-unique-signaling-system-for-Europe.pdf

[5] https://transport.ec.europa.eu/transport-modes/rail/ertms/history-ertms_en

[6] https://s-bahn.hamburg/magazin/s-bahn/digitale-s-bahn-hamburg-2-0.html

[7] https://www.ertms.net/about-ertms/about-unsig/

[8] https://ertms.be/mission

[9] https://www.ertms.net/wp-content/uploads/2021/07/ERTMS_Factsheet_8_UNISIG.pdf

[10] https://digitale-schiene-deutschland.de/en/Digital-Node-Stuttgart

[11] https://transport.ec.europa.eu/transport-modes/rail/ertms/what-are-benefits_en

[12] https://transport.ec.europa.eu/transport-modes/rail/ertms/preparing-future-evolution_en