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Institution of Railway Signal Engineers
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 IRSE(HK) Newsletter > News
 Issue 06 @ March 2010 

What is ERTMS/ETCS ?

Anthea Ngai
IRSE(HK) Executive Member
Hyder Consulting Pty Ltd


ERTMS is the European Railway Traffic Management System that was developed and specified by the European signalling suppliers (UNISIG), European Railways and the GSM-R industry acting together under the guidance of the EC.   The major members of UNISIG are Alstom Transport, Ansaldo STS, Bombardier Transportation, Invensys Rail Group, Siemens Mobility and Thales.

Over the year, over 20 different train control systems (TBL, EBICAB, INDUSI, KVB, LZB, TVM, ATB, etc) have been developed and operated by individual European Railways according to their national requirements on technical standards and operating rules.  However, the diversity does not meet the long-term reliability and efficiency requirements.  The automatic train protection (ATP) systems in use are non-compatible.  A train must be equipped with different ATP systems as it travels along different lines across the country borders.  Sometimes, it even requires changing locomotive or driver at frontiers as each country generally has its own signalling system for which the drivers have to be trained. 

The additional ATP systems take up a lot of space on-board.  It also adds to travel time, operational and maintenance costs.  Unifying the multiple signalling systems will provide better interoperability of freight and passenger rail services, minimise technical and cultural problems of cross-border rail operations, reduce costs, improve the overall quality of rail transport and increase competitiveness.


In December 1989, European Transport minister decided to formulate a strategy to develop a single Train Control System standard to apply across Europe.  A group of railway experts started to develop the requirements specification of European Train Control System (ETCS) as the base for industrial development.  The project framework included new on-board equipment, a new discontinuous and a new continuous data transmission system.  At the end of 1993, the EU council issued an Interoperability Directive and a decision was made to create a structure to define the Technical Specification for Interoperability.

In 1996, the EU decided that European Rail Traffic Management System (ERTMS) would become the standard for all high-speed lines. The EU Council Directives 96/48/EC and 1001/16/EC with respect to the interoperability of the trans-European high-speed rail system and conventional rail system were developed.  ETCS is developed as part of the ERTMS initiative. 

What is ERTMS?

ERTMS comprises trackside and trainborne systems and utilises an in-cab signalling and ATP element called ETCS (European Train Control System).  ETCS is the train control system and GSM-R (Global System for Mobile Communications – Railways) is the new radio system for voice and data communication. 


The two subsystems together form ERTMS, the new signalling and traffic management system which enabling interoperability throughout the European railway network.

ETCS is a signalling, control and train protection system developed and promoted by European Commission.  The system aims to standardise the signalling and train control systems and remove the hindrance to the development of international rail traffic.  It specifies for compliance with the High Speed and Conventional Interoperability Directives. 

ETCS is in fact an ATP system, based on cab signalling and intermittent and/or continuous track to train data transmission.  It provides an inherently safe operational environment for the movement of trains throughout the network, while facilitating a greater network carrying capacity.  It does this through the real-time monitoring, capture and analysis of data relating to movement authorities, precise train location, train speed, braking curves and system integrity.  Based upon the analysis of this data, appropriate control orders are issued so that rail traffic operates with the shortest, most efficient, but safest headways.

GSM-R is a radio system that provides voice and data communication between the track and the train.  It is based on standard GSM using frequencies specifically reserved for rail application with certain specific and advanced functions.

Levels of ETCS

ETCS is divided up into different equipment and functional levels.  The definition of the level depends on how the route is equipped and the way in which information is transmitted to the train.  The scope and interface of ETCS at trackside level vary considerably for the three application levels.

ETCS – Level 1
ETCS Level 1 is a cab signalling system that can be overlay or used in conjunction with existing signalling systems.  Lineside signals are generally retained and block control is achieved in the conventional manner by the interlocking, based on the information detected by track circuits or axle counters.

It is a system based on intermittent track-to-train communication.  Balises, which are linked to the signals or interlockings via the Lineside Electronic Unit (LEU), transmit route data as movement authority to the trains.  The on-board computer continually monitors and calculates the maximum permitted speed and the braking curve. 

Figure 1 ETCS Level 1 Balise without infill
(Figure captured from:

To increase the capacity, additional infill balises between the distant and the main signal are installed.  The new aspect status is updated more frequently via radio using GSM-R corresponding to a balise in advance of the train.   As a consequence, a train approaching the application zone of a more restrictive condition can revoke braking as soon as the ‘signal clears’ without waiting to reach the balise itself.

Figure 2 ETCS Level 1 Balise with infill
(Figure captured from:

The World's first commercial application of the ETCS reached Bulgaria in October 2001.  The 250km section of the 430km Sofia-Burgas line has been completed by the Austrian arm of Alcatel Transport Automation Solutions (TAS).  Today, the ETCS Level 1 system is operating in many countries, such as Austria, Hungary, Romania, etc.  It is also deployed on the Beijing–Tianjin Intercity Rail line in northeast China.

ETCS – Level 2
At ETCS Level 2, the transmission of variable data between the Radio Block Center and the trains is based on continuous digital radio-based system, GSM-R, in the 900 MHz frequency band.

This system can be used with or without lineside signalling as a backup (subject to operating rules).   It enables safe operation at higher speeds, and provides a near instantaneous update of the movement authority and display in the cab for the driver through Radio Block Center using GSM-R.  The Balises are used at this level as passive positioning beacons. All trains automatically report their exact position and direction of travel to the RBC at regular intervals.   However, the track detection and hence the train integrity supervision still remain in place at the trackside.  

The on-board computer continuously monitors the transferred data from balise including movement authorities, the status and characteristics of the track ahead and the distance to the next balise.  Between two positioning balises, the train determines its position via sensors (axle transducers, accelerometer and radar). The positioning balise is used as a reference point to calibrate distance measurement errors.  The on-board computer also compares the train’s actual speed to the permitted speed.  It applies mandatory brake automatically to bring the train speed to below the permitted speed.

Figure 3 ETCS Level 2 Balise with GSM-R and Radio Block Center
(Figure captured from:

Several ETCS Level 2 installations are found in Germany, Switzerland, Luxembourg, Italy and Netherlands nowadays.  In December 2008, Denmark announced plans for the conversion of its entire national network to ETCS Level 2.   The conversion will begin in 2009 and is projected for completion in 2021.

ETCS – Level 3
In Level 3, ETCS goes beyond the pure train protection functionality with the implementation of fully continuous radio-based train spacing.  ETCS replaces the lineside signals as well as the trackside detection devices.   The train driver views all speed and signalling information on in-cab displays and no signals are required along the line.

As in ETCS Level 2, trains find their position themselves by means of positioning balises and sensors (axle transducers, accelerometer and radar) and must also be capable of determining train integrity on-board to the very highest degree of reliability.

The location of the train is determined by the train odometry and reported to the trackside radio block centre via the GSM-R radio transmission.  In this configuration, the interlocking no longer controls train spacing.  It enables the railway to operate at the highest possible capacity.  The interlocking and RBC exchange route setting information.   The interlocking determines which point on the route the train has safely cleared and grants another movement authority to the following trains up to this point. 

This configuration offers a great simplification with cost reduction of the equipment in the track and an independence from rigidly structured fixed block intervals.  Train headways come close to the principle of operation with absolute braking distance spacing known as “moving block”.  

Figure 4 ETCS Level 3 Balise with GSM-R and Radio Block Center
(Figure captured from:

The system has been specified but is not yet under development anywhere and it is still in a conceptual phase.

Summary of ETCS Level

Table 1 Summary of different ETCS level

Benefit of ERTMS

Compared with the traditional signalling systems, ERTMS is clearly more flexible and advanced with regard to conveying information.  It provides interoperability cross-border railway traffic. There are also many other benefits of implementing the ERTMS such as,
  • less trackside equipment and major equipment reduction the leads to fewer breakdowns/disruptions
  • increase capacity, provide quicker and more flexible train movements
  • improved punctuality
  • higher operational throughput and lower operations and maintenance cost
  • possible to have line speeds of up to 500 km/h
  • open market for signalling systems and increased competition by admitting more suppliers

ERTMS Implementation Status

After years of development and studies, ERTMS has rolled out successfully on both high speed and conventional lines. The EU has initiated six ERTMS corridors and some other trans-European transport network (TEN-T) and is now considering an EU-wide master plan on ERTMS migration. 

Today, over 2000km lines equipped with ETCS is in operations in Europe.  The roll-out of ETCS spreads worldwide to South Korea, Taiwan and Australia.

Table 2 Implementation Status in Europe


The ERTMS is gradually replacing the existing incompatible systems throughout Europe.  This will bring substantial benefits to the railway sector in terms of maintenance cost savings, safety, reliability, punctuality and traffic capacity.  It will definitely boost international freight and passenger transport.  The increasing implementation of ERTMS outside Europe such as Algeria, China, India, Mexico, Saudi Arabia, South Korea, Taiwan and Turkey also demonstrates its success.

However, the elaboration and implementation of Europe-wide or worldwide ETCS migration strategies will be a long, sizeable and complex process.  There are also lots of hurdles to be overcome considering the historical, political and financial issues.  A coherent approach with all stakeholders to speed up the process is necessary.  An integrated strategy for migration and implementation programme should be defined clearly and adequate finance support is critical.  The full benefits of ERTMS will only become visible with reaching critical mass.

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