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Automatic Train Protection - ATP

Demystified

ATP


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Table of Contents

1. _________________ 3 Introduction ____ 3 1.1. What Does the Signalling NOT Do ? ______________________ 3 1.2. What is ATP ?

2. ______________ 4 ATP for RailCorp ________ 4 2.1. Why does RailCorp want ATP ? _______________________ 4 2.2. Why ETCS ?

3. _______________ 5 All About ETCS ______________ 5 3.1. How Does ETCS Work ? ______________________ 5 3.2. ETCS Level 1 ___________ 6 3.3. What Does the Driver See ? ______________________ 6 3.4. ETCS Level 2 _________________ 7 3.5. Level 3 and Beyond

4. Who Makes ETCS ? Who Uses ETCS ?__________________________ 7

_____________ 7 4.1. How did ETCS Develop ? ______________ 7 4.2. Who are the Suppliers ? _______________ 8 4.3. Where is ETCS Used ? ________________________ 8 4.4. Conclusion

August 2008

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1. Introduction 1.2. What is ATP ? Many signalling systems provide additional

protection beyond the signal at STOP. This is called an overlap and is to safeguard against a driver becoming incapacitated or misjudging braking.

Automatic Train Protection (ATP) seeks to provide additional protection by taking the lineside signalling information into the train.

1.1. What Does the Signalling NOT Do ?

Railway signalling systems have developed incrementally since the days of the railway policeman with his red flag and trains spaced by time interval. Contemporary RailCorp signalling is a fixed block system – lineside signals delineating ‘fixed blocks’ of track which are proved clear of other trains before the signal protecting the block can clear.

The first true ATP systems were developed in the 1980s. To begin with each country and each supplier developed their own systems and a multitude of systems emerged with various methods of transmitting signalling information to the train.

The overlap distance provided in the RailCorp signalling system is calculated as emergency braking distance for a train passing the signal at line speed. This can be quite long where line speeds are high.

The signalling system provides layers of protection that guard against signaller error, but the only medium which conveys safety information to the driver is visual observation of the signals.

SNCF Crocodile – physical electrical contact

SBB Signum –magnetic induction

DBAG LZB –radio loop

SNCF Crocodile – physical electrical contact

SBB Signum –magnetic induction

DBAG LZB –radio loop

Unlike a motor car, a train often cannot stop within the distance visible to the driver ahead:

Accidents such as Ladbroke Grove (31 deaths) in England and Beresfield (6 injuries and major damage) in the Hunter Valley bear testament to the dangers of a driver failing to react to a signal at STOP.

Stopping Distance Travelling at 100 kph

Motor car 60 metres Modern electric train 800 metres Long heavy freight train up to 2 km

The signalling system includes no means to ensure that the train is driven within the permitted line speed. There are many places on the network where curves or turnouts for diverging routes require the train to slow significantly.

So train drivers need advance warning of the signal ahead. In the RailCorp metropolitan area, the signal before a signal showing STOP would display: GREEN over RED – a Caution Aspect

If signals are closer together than braking distance the previous signal would display: Accidents such as Amagasaki (107 deaths) in

Japan or Waterfall (7 deaths) to the south of Sydney are examples where the train speed was higher than the safe speed for track conditions.

GREEN over YELLOW – a Medium Aspect Trackside ATP equipment interfaces to the

signalling system and transmits relevant data to the train. This can include information such as signal aspect, permitted line speed, distance to next signal etc.

Signals are arranged so that the driver always has a braking distance to the signal at STOP from the first warning signal. The diagram shows the sequence of aspects:

Direction of Travel

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2. ATP for RailCorp 2.2. Why ETCS ? On board the train the ATP system processes

the data and can indicate signal status or permitted movement authority to the driver. The comprehensive review assessed

potential ATP systems against several key criteria, including technical capability, economic viability and level of risk mitigation. The key issues upon which the recommendation was based were:

2.1. Why does RailCorp want ATP ? The onboard system will also supervise actual train speed and location against the movement authority generated by the signalling system. This is the ‘automatic’ part of the system, which will apply the brakes automatically if the driver fails to respond to movement authority limits or speed restrictions.

RailCorp and its predecessor organisations have assessed and evaluated various ATP options since the mid 1980s. In fact a first generation system was trialled in 1986 on the line between Liverpool and Campbelltown, but no further installation was authorised.

• ETCS is a high integrity safety system that controls risks associated with trains overspeeding or exceeding their limit of authority. The major impetus to recent consideration of

ATP was triggered by the Waterfall accident in January 2003, which was caused by a train overspeeding and derailing.

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• It is available ‘off the shelf’ from multiple suppliers designing to common specifications.

• ETCS is mandated by the EU as the standard ATP for use in Europe and is a mature technology with a large user base.

In May 2003 StateRail initiated a Train Protection Study to identify potential systems that could have prevented the accident. Halcrow were engaged to conduct a worldwide search and evaluation of available technologies which could control overspeeding.

• It is flexible in its application and can be overlaid, with minimal impact, to existing signalling systems or rolling stock.

• It would provide a major risk mitigation of RailCorp’s direct risk.

The final report of the special commission of inquiry set up by the Government to investigate the Waterfall accident included a recommendation that: “RailCorp should progressively implement automatic train protection within a reasonable time.”

• Economic evaluation gave a marginally negative outcome, but some key potential benefits could not be quantified without further work.

• ETCS has a defined upgrade path to allow future functionality enhancements.

In response to the recommendation RailCorp committed to provide a comprehensive review of ATP options to Government. The review built upon the previous Halcrow study and resulted in a recommendation that RailCorp adopt the European Train Control System (ETCS) as its chosen ATP system.

• It has the potential to enable future signalling changes which will deliver significant capacity benefits.

In comparison to lineside signalling, ATP is predictive rather than reactive. The system will supervise the train in accordance with train’s predicted braking performance approaching a signal at STOP, rather than providing an overlap margin of error after having passed a signal at STOP.

The RailCorp Board took forward the recommendation by approving a pilot trial of ETCS on the Blue Mountains line.

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3. All About ETCS Three contracts were awarded, each

requiring suppliers to fit ETCS trackside equipment to approximately 15 km of track and ETCS onboard equipment to a train.

3.2. ETCS Level 1

ETCS level 1 is an overlay system that can be easily interfaced to existing signalling systems. It interfaces to signal aspect controls to generate MAs, which can be enhanced with additional inputs to provide better information than can be interpreted from the visual lineside signal aspects.

3.1. How Does ETCS Work ?

ETCS has been conceived to operate at three levels. While the operational concepts are common across these three levels, the means of deriving dynamic system information and the means of transmission to and from the train varies between levels. Transmission to the train is via balises (radio

transponders), which are predominantly located in pairs at each signal (yellow balises between rails in the picture on the left). Transmission is powered by the energy radiated by the antenna mounted on the train, enabling the balises to work without trackside power supply.

The common features are:

• Generation of movement authorities (MA) which determine the safe movement limits and safe speed for each train.

• Transmission of the MAs from trackside to each train.

• Calculation on board the train of a safe speed profile within the limits of the current valid MA and based upon the train characteristics, such as braking performance, train weight and length etc. (see diagram below)

On board the train, balise messages are received by the antenna and passed to the European Vital Computer (EVC), which is the brain of the onboard system. The EVC also receives information from tachometers and radar mounted on the bogie to keep track of train speed and distance from the last balise location.

• Presentation of the speed profile to the driver.

• Supervision of train movement against

the calculated speed profile, with automatic brake intervention should the train exceed a predetermined margin outside the speed profile.

The EVC combines the information and calculates the safe speed profile, based upon trackside and onboard data.

Trial running took place between November 2007 and April 2008, successfully demonstrating the operation of ETCS and the ease with which it can be overlaid on the RailCorp signalling system and fleet.

The RailCorp pilot trial demonstrated an ETCS level 1 system.

Train

Spee

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Trackside generated MA

On board calculated speed profile

The pilot trial included a collaborative development group, comprising ETCS experts from each of the suppliers along with key RailCorp stakeholders. The group initially formulated the application rules for the pilot trial and then, building upon the lessons from the trial, developed these rules into a blueprint for applying ETCS to the RailCorp network and fleet.

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3.3. What Does the Driver See ? ETCS will only intervene if actual train speed

is outside the permitted limits. Also displayed are, a vertical bar showing gradients and key track features, such as tunnels, bridges etc., which appear to the left of the gradient bar.

The driver is presented with details of the current MA on the Driver Machine Interface (DMI), which also provides a means for driver input to the system.

For example in normal running the driver must keep train speed within the permitted line speed. If the speed exceeds line speed, ETCS will initially sound a single tone and speed indications change to orange.

Below the speed dial is an information and monitoring area which can display text messages or various symbols depicting ETCS status: If train speed exceeds line speed by a

predetermined margin, a continuous alarm sounds with indications remaining orange.

If train speed increases above a further margin, the service brake is automatically applied and indications change to red.

ETCS Level 1

As a final safeguard, should the train still not be slowed sufficiently, the emergency brake will be applied and the train will be brought to a stand.

Full Supervision mode

To the right of the planning area and at the bottom of the screen are areas for driver input. This can either be in the form of touch screen keys or buttons around the edge of the screen area.

3.4. ETCS Level 2

There are four key areas on the DMI. The speed dial area contains a conventional speedometer display, with an additional band around the outer edge showing permitted speed (Circular Speed Gauge - CSG).

ETCS level 2 is designed to overcome the intermittent nature of the track to train transmission of level 1 and avoids the need for lineside signals to be retained. ETCS does not provide automatic control of

the train. The driver is provided with information allowing him to drive in an optimised way. For example, once the train is within the braking zone to a signal at STOP, the speed pointer and CSG change to

Transmission to the train is via the radio system and GSM-R, a complimentary system of ETCS, has been designed to provide the radio transmission platform.

To the right of the speed dial is the planning area, which shows information about the route ahead. The display scrolls down the screen as the train moves forward along the track.

Conventional block signalling is retained, but the signalling interlocking is interfaced directly to a Radio Block Centre (RBC). The RBC translates signal route availability into ETCS movement authorities, which are transmitted to the train via the GSM-R radio.

Yellow. The CSG reduces with the permitted speed as the train nears the signal. The driver must keep the train speed within the reducing permitted speed.

A simplified speed profile is shown in the right hand half, with triangular target makers showing line speed change points or signals at STOP (zero speed marker). The horizontal yellow line indicates where braking should commence to reduce speed to the first speed change.

This continuous transmission means that changes of state in the signalling system are transmitted to the train as they occur, rather than waiting for the next balise to be read.

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4. Who Makes ETCS ?

Who Uses ETCS ?

3.5. Level 3 and Beyond Formal work on developing ETCS level 3 is not currently being progressed and it seems unlikely that it will proceed until the latest version of the level 1 and 2 specifications have been finalised and outstanding issues from operational systems have been resolved.

Whilst ETCS levels 1 and 2 are in full commercial operation throughout Europe and elsewhere, level 3 has not yet been developed into a reality.

4.1. How did ETCS Develop ?

ETCS has its origins in European Union Council Directive 96/48/EC of July 1996 on the interoperability of the European high speed rail system which required the development of systems to permit seamless rail traffic flow across internal EU frontiers.

The concept is that the lineside signalling system would be required only for junction areas to control point operation. On plain line sections trains would track their own position, as for levels 1 and 2, transmitting their position via GSM-R radio to the RBC and hence into the signalling interlocking. MAs would be transmitted from interlocking, via RBC to the train as in level 2.

Currently ETCS does not include any plans for Automatic Train Operation (ATO). However ATO systems already in use are generally designed as an overlay to an underlying train protection system. The EU initiated the creation of technical

specifications for the European Rail Traffic Management System (ERTMS), which has two key building blocks, a common European radio system for railways, GSM-R and a common European train protection system, ETCS.

The level 3 concept would provide true ‘moving block’ signalling, where the occupied block is continuously released behind the train and is not tied to fixed trackside train detection sections. The European Railway Agency (ERA) is now

the system authority for ERTMS, managing the functional requirements of the system, while UNISIG, a consortium of the 6 major European signalling suppliers, is tasked with the development of technical specifications for ETCS.

The first moves towards level 3 are currently being made in Sweden, with a trial of ETCS Regional, a part way step towards level 3.

Copenhagen Metro

The main difficulties inhibiting the development of level 3 are:

Thus far the only rail networks to employ ATO have been metro style systems, where the trains have consistent performance characteristics and the right of way is safeguarded from vandals and trespassers.

4.2. Who are the Suppliers ? • the complexity of the centralised computing task of dynamically tracking all trains in the network ETCS is supplied by the six members of the

UNISIG consortium. • the calculation of valid MAs, as additional

parameters, such as train speed, must be included in the calculation of the safe block ahead of a train.

• the need to continuously prove train integrity, i.e. all train vehicles remain coupled.

• the safety validation, availability and reliability of the system.

RailCorp could potentially overlay ATO on ETCS in the future. This would be most feasible in the high density core of the network, such as the City Underground or Eastern Suburbs line, where the most benefits would occur. It is unlikely however, that ATO could be effectively applied in the mixed traffic sections of the network in the foreseeable future.

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All six suppliers have a presence in Australia to a varying degree.

All new European high speed lines are being equipped with ETCS and the EU is providing funding to assist member states to fit the 6 key Trans European Network corridors, primarily for international freight services.

Westinghouse Rail Systems has a long standing signalling history extending back to the 19th century. It has been part of the Invensys Group since the 1990s and has had a major signalling presence in Australia going back over many years. For the pilot trial it teamed with Bombardier, to leverage Bombardier’s greater onboard expertise.

Alstom’s Australasian arm was sold by the French parent to United Group in 2005, however Alstom remain one of United Group’s key technology partners. They have a long record of signalling product supply and major resignalling within Australia and are also a key player in the Rolling Stock field through ownership of Goninan.

ETCS has also spread beyond Europe and projects are currently under way in China, India, Mexico, Saudi Arabia, South Korea and Taiwan as well as our own successful pilot trial.

4.3. Where is ETCS Used ?

The first ETCS level 1 system to be successfully commissioned for commercial operation was on the Sofia to Burgas corridor in Bulgaria in October 2001 and the first level 2 system was on the Rome to Naples high speed line, which opened in December 2005.

ERTMS Implementation status – June 2008 Ansaldo is an Italian based multinational whose signalling presence in Australia is through the acquisition of Union Switch & Signal. They are a major supplier of signalling interlocking equipment to RailCorp and have a record of signalling project design and delivery, chiefly for ARTC.

Total No. of Route Track

Bombardier’s presence in Australia has been chiefly in the rolling stock field. For the pilot trial they teamed with Westinghouse, providing the on train ETCS equipment and expertise.

Siemens has had a presence in Australia since 1894, chiefly in the power engineering and communications field. Its main involvement in NSW has been the supplier and maintainer of MetroNet, RailCorp’s current train radio system.

Thales is a major player in the ETCS field within Europe, having acquired the business from Alcatel in 2006. In Australia however, its presence is chiefly in the defence industry, based on its acquisition of ADI. In Australia Thales is only now establishing a capability in the signalling field.

Since these successful beginnings ETCS roll out has gathered pace and a number of lines have been fitted and brought into commercial service

ETCS Lines in OperationLevel 1Level 2



Vehicles Length Km Length Km

Europe 3,992 10,434 16,948

Rest of 2,140 10,034 16,156 the World

Total 6,132 20,468 33,104

Figures indicate lines and rolling stock in operation as well as contracts signed as at July 2007.

4.4. Conclusion

ETCS appears destined to become the de facto standard ATP system for mixed traffic and high speed railways throughout much of the world for the foreseeable future. Being supported by 6 major signalling suppliers, it is the only true multi-vender ATP system available to rail administrations and is likely to have extended system availability and supplier support.

The ease of overlay to existing signalling systems makes it ideal for retro-fitting existing rail networks. The migration path between the current and planned ETCS levels means that the users are not locked in to the initially selected functionality.

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