A Brief Introduction to the RailCorp ATP System v3pt0

December 2011 Page 1 of 24

A brief introduction to the RailCorp Automatic Train Protection (ATP) system

Version 3.0


December 2011 Page 2 of 24 Version 3.0

Table of contents Introduction ................................................................................................................................ 4 What is Automatic Train Protection (ATP)?............................................................................. 4 Components of the system ....................................................................................................... 5

ATP trackside equipment ................................................................................................................................ 5 ATP onboard equipment.................................................................................................................................. 6

How the system works............................................................................................................... 9 Train information is stored in the ATP onboard equipment......................................................................... 9 Information is sent from ATP trackside equipment ...................................................................................... 9 Track information is received by the ATP onboard equipment.................................................................... 9 Track and train information are processed by the ATP onboard equipment.............................................. 9 If unsafe conditions are entered, the onboard ATP equipment intervenes .............................................. 10

Some key ATP concepts.......................................................................................................... 12 Movement authorities, ends of authorities and supervised locations ...................................................... 12 Release speeds .............................................................................................................................................. 13 Infill.................................................................................................................................................................. 15 Managing a train through a section.............................................................................................................. 17

Some RailCorp ATP system principles .................................................................................. 21 Drivers will generally drive in the same manner as previously ................................................................. 21 Drivers will continue to obey the rules for responding to signals and passing signals at STOP........... 21 Different modes for different movements .................................................................................................... 21

FAQs.......................................................................................................................................... 22 How will the ATP system help RailCorp?..................................................................................................... 22

Safety.................................................................................................................................................... 22 Capacity ................................................................................................................................................ 22

Can all Drivers operate an ATP-fitted train? ................................................................................................ 22 Will ATP prevent all SPADs?......................................................................................................................... 23 Will the DMI distract Drivers from their normal driving tasks?.................................................................. 23 What if the ATP trackside equipment fails?................................................................................................. 23 What if the ATP onboard equipment fails? .................................................................................................. 23 What if a signal returns to stop as a train approaches?............................................................................. 24 What will ATP-fitted trains do in areas without ATP trackside equipment? ............................................. 24 What might happen in the future? ................................................................................................................ 24

Conclusion................................................................................................................................ 24



Table of figures Figure 1: Common ATP trackside equipment ...................................................................... 6 Figure 2: ATP onboard equipment..................................................................................... 7 Figure 3: Sample DMI layout ........................................................................................... 8 Figure 4: Intervention sequence..................................................................................... 10 Figure 5: Relationship between some signalling concepts and ATP concepts .......................... 12 Figure 6: EP brake and emergency brake intervention curves calculated from previous balise

group information........................................................................................... 13 Figure 7: Effect of release speed when approaching a signal that has just cleared.................. 14 Figure 8: Approach to a signal that has cleared, with no infill.............................................. 15 Figure 9: Approach to a signal that has cleared, with balise infill. ........................................ 16 Figure 10: Approach to a signal that has cleared, with Euroloop infill. .................................... 16 Figure 11: Approaching a signal indicating proceed............................................................. 17 Figure 12: Train receives a movement authority at BG1 ...................................................... 17 Figure 13: Train receives a movement authority at BG2 ...................................................... 18 Figure 14: Movement authority is not extended when passing BG3 ....................................... 18 Figure 15: Train stopped at signal S4, balise group BG4 has not been read ............................ 19 Figure 16: Train accelerating from stop towards signal S4.................................................... 19 Figure 17: Train getting a new movement authority as it passes balise group BG4 .................. 20



Introduction This document is intended only as an introduction to the Automatic Train Protection system that will be installed in the RailCorp network, and not all aspects or features of the system are described. As such, it should not be used for any purpose other than to get a general idea of what the system is and how it works. It is not a training document.

In particular, the examples given mostly relate to signalled through movements on running lines. Shunting, failure and other such modes are not described in any detail.

Please also note that the exact specifications for some aspects of the ATP system have not yet been finalised, and so may differ somewhat from their description here.

What is Automatic Train Protection (ATP)? ATP is a train safety system. It uses trackside and on-train equipment to identify some potentially unsafe conditions, and if necessary the on-train equipment will warn the Driver, and slow or stop the train before the conditions can become dangerous. Four specific functions of the system are to:

• enforce track speed limits

• give Drivers advance notice about the track ahead such as signals at STOP and track speeds

• prevent trains from approaching a signal at STOP at too great a speed

• prevent trains from passing the overlaps beyond signals at STOP.

It is important to note that the system will not prevent all SPADs, however it should greatly reduce both the number and the potential consequences of SPADs.

The RailCorp ATP system is based on the European Train Control System (ETCS). This specification has been chosen because:

• it is a mature system, used extensively in Europe and elsewhere, with a proven safety record

• ATP trackside and onboard equipment is available “off the shelf” from a number of suppliers, the equipment from all suppliers will be compatible

• it can be overlaid on RailCorp’s existing signalling system

• it is a flexible system that allows for a pre-defined future upgrade path.



There are three levels of ETCS. The initial RailCorp system will be ETCS Level 1, and the remainder of this document is focused on the characteristics of that level. This has the potential to be upgraded to Level 2 or Level 3 in the future. Brief descriptions of the higher levels are given in the answer to the What might happen in the future question in the FAQs.

Components of the system The ATP system comprises ATP trackside equipment and ATP onboard equipment.

ATP trackside equipment Lineside Electronic Units (LEUs) are connected to the signalling systems, and convey information about the infrastructure, including signal indications, to ATP transponders.

ATP transponders include balises, Euroloops and radio infill units, of which balises are most commonly used. They transmit information to trains, which can include:

• signalling information, including how far the train may travel

• the identification of and distance to transponders ahead

• track speeds

• track gradients

• location information including:

no stopping areas

level crossings

level transition borders, i.e. the boundaries between ATP-fitted and ATP-unfitted areas, or between areas with different Levels of ATP system

NOTE: The exact details that will be used in the RailCorp ATP system have not yet been finalised.

Balises are small transponders located on the track which transmit:

• to trains only at a single location

• only once to each passing train.

Balises are unpowered, and are energised and read by the antennas of passing trains.

One or more balises that act in unison, and are closely nearby, are known as a balise group. Balise groups can send different messages to trains based on:

• the state of any linked signalling equipment

• the direction of travel of trains reading the balise group.


Euroloops are transponders along a length of track which transmit continuously:

• to trains as they travel onto the Euroloop

• to trains anywhere on the Euroloop when information changes.

Euroloops have not yet been approved for use in RailCorp’s system.

Radio infill units act similarly to Euroloops, but use radio to transmit signal information to nearby trains.

Radio infill units and Euroloops cannot transmit relative distance information. All radio infill units and Euroloops have associated balises which transmit details about their positions and identification to trains.

Figure 1 depicts a portion of track with some common ATP trackside equipment.

Figure 1: Common ATP trackside equipment

ATP onboard equipment ATP onboard equipment comprises:

• an antenna, which picks up signals from ATP transponders

• a processing unit, which manages track and train data to calculate safe speeds (which may be zero)

• a control and display unit in the Drivers cab known as a Driver Machine Interface (DMI)

• an odometer to measure the distance travelled, which comprises wheel sensors, radar and an accelerometer

• components to interact with the train’s electrical, power and brake systems.



Figure 2 depicts ATP onboard equipment.

Figure 2: ATP onboard equipment

NOTE: Antennas might be placed in different spots on different train types, but they will always be on the leading vehicle.

The DMI has the following key areas:

• a speedometer on the left, showing the current speed, and usually a circular speed gauge outside the speed dial showing the allowable speed

• a planning area towards the right, showing information about the track ahead, which scrolls as the train progresses. It can show:

a speed profile area towards the right showing changes in track speed

signals at STOP

track gradients.

• an information and monitoring area at the bottom, which displays ATP status, text messages and warnings

• touch screen buttons to allow Driver input and acknowledgement

• when approaching a lower speed area or stopping location, a distance to target bar on the left..



Figure 3 shows the general layout of a DMI.

Figure 3: Sample DMI layout

NOTE: Final screen layout may vary a little from that shown.




How the system works

Train information is stored in the ATP onboard equipment Information about the particular train class is stored on each train’s ATP onboard equipment. This information includes:

• braking characteristics for the electro-pneumatic (EP) brake and emergency brake

• the maximum speed that the train may travel.

Additionally, the Driver must enter some information into the ATP onboard equipment before each trip, including:

• the number of cars in the consist

• any brakes that are isolated.

NOTE: This information must be re-entered or confirmed each time a cab is cut-in, and after some mode changes.

Information is sent from ATP trackside equipment Lineside electronic units (LEUs) read information from interlocked signalling equipment. This information is passed to transponders (balises and Euroloops). Balises can also store track information such as gradients and speed limits, and transmit both the signalling and track information to trains passing over them.

For example, a balise group at a PROCEED signal will transmit information that could include:

• the distance to the next signal ahead

• the distance that the system will allow the train to run

• the different track speeds that apply ahead

• the different track gradients ahead.

Track information is received by the ATP onboard equipment Passing trains read the information transmitted by ATP transponders.

Track and train information are processed by the ATP onboard equipment

The track information received from ATP transponders, the train information stored in the ATP onboard equipment, and the information entered by the Driver, is combined by the ATP onboard equipment. This combined information is then used by the ATP onboard equipment to calculate safe speeds of travel along the track ahead.


Drivers will receive advance notice of changes in track speed and of locations at which the train must otherwise be stopped or slowed. For some wrong running-direction speed restrictions, this notice will be in the form of text messages, but usually the indications are given by the circular speed gauge (CSG).

If unsafe conditions are entered, the onboard ATP equipment intervenes

Normally, the Driver of a train will maintain the train speed within the calculated safe speed. If, however, the train exceeds the safe speed, an escalating series of interventions will be initiated by the ATP onboard equipment. As the train speed increases (or the safe speed reduces):

• a warning tone will sound to alert the Driver that the safe speed has been exceeded

• the system will prevent power from being applied

• the system will apply the EP brake

• the system will apply the emergency brake.

Figure 4 depicts the intervention sequence as a train approaches an area with a lower track speed.

Figure 4: Intervention sequence




NOTE: The pre-indication location is the location at which the Driver will receive advice that the train will need to be braked.

In Figure 4, the unbraked speed represents a train that does not slow down as it approaches the location where there is a reduction in track speed. After the train has passed the calculated start of braking location:

1. The unbraked speed would first cross the warning curve, and the system would alert the Driver by sounding an alarm and by indications on the DMI. The system will also cut off traction power.

2. If the train were to travel further without braking, the unbraked speed would cross the EP brake intervention curve, and the EP brake would be applied until the Driver acknowledges the intervention.

3. If the train speed still does not reduce sufficiently, for example because of slippery rails, the unbraked speed would cross the emergency brake intervention curve, and the emergency brake will be applied.

It should be noted that EP brake and emergency brake calculations have different safety margins, so that the calculated stopping distance for an emergency brake intervention is generally longer than the calculated stopping distance for an EP brake intervention. For speed change calculations, the assumed location allows for possible error in the train’s location, shown in Figure 4 as the odometer confidence interval, so that the front of the train will definitely be under the new speed as it passes the speed sign.


Some key ATP concepts

Movement authorities, ends of authorities and supervised locations

The ATP system in some ways mimics the signalling system, but for the RailCorp rollout of ETCS Level 1 it will not be an in-cab signalling system.

Signals give proceed authorities, which allow trains to travel as far as the next signal. Similarly, the ATP system uses movement authorities, transmitted by transponders, which enable trains to be moved towards a specified location ahead. Movement authorities are usually issued at the balise group just before a signal.

A movement authority includes:

• the track speeds that apply

• an end of authority location

• a supervised location.

The end of authority is a location to which the train can be moved, and for through movements a location before which the ATP system expects that a new movement authority will be received by the train, which will usually be at a signal ahead.

The supervised location is the location which the ATP system will not normally allow the train to pass. If necessary, the system will intervene to apply the emergency brake to make sure that the train is stopped.

For movements towards a signal at STOP, the supervised location is actually past the signal, and can be thought of as similar to a signalling overlap.

Figure 5 shows related signalling and ATP concepts. The top part of the diagram shows current signalling concepts, the lower part shows ATP concepts overlaid.

Figure 5: Relationship between some signalling concepts and ATP concepts



The fact that the EP brake intervention ends at the End of authority and the emergency brake intervention ends at the supervised location, together with the EP brake intervention occurring at a lower speed, results in there being a safety margin as a train approaches the end of authority, as shown in Figure 6.

Figure 6: EP brake and emergency brake intervention curves calculated from previous balise group information

Release speeds If a signal clears as a train approaches, there is no safety reason why the Driver should not accelerate up to track speed. However, until the balise group at the signal is read, if there is no infill (see following section), the ATP system would intervene to prevent the train from travelling faster than the speed that would enable the train to be stopped at the signal.

For this reason, a release speed is applied as a train approaches an end of authority at a signal. This takes advantage of the safety margin, and is calculated such that a train passing a signal at stop would still be stopped by an emergency intervention before reaching the Supervised Location.

If the train is travelling more slowly than the release speed, the EP brake intervention will be suppressed and not automatically slow the train further. If the train exceeds the release speed after the EP brake intervention curve has fallen below it, there are no warnings, and the emergency brake is immediately applied.

If the signal remains at STOP, the Driver must still stop the train before the signal as normal, and if the train were to pass the signal at STOP, an emergency brake intervention would occur to stop the train before the supervised location.



If the signal clears, however, the Driver does not need to slow the train as much as they would have to if there were no release speed.

The effect of release speed is shown in Figure 7, with the signal that was the end of authority having cleared.

Figure 7: Effect of release speed when approaching a signal that has just cleared

The release speed can be calculated by the onboard ATP equipment or a pre-determined value can be transmitted by the trackside ATP equipment. In some cases where the Supervised Location is very close to the End of Authority, the release speed can be zero. In other cases, where the Supervised Location is a long way past the End of Authority, the release speed can be track speed, meaning that the system will allow a train to approach a signal at STOP at track speed.

NOTE: Keep in mind that the ATP system will not prevent all SPADs.



Infill Another way that efficiency is maintained is by the concept of infill.

If a train approaches a signal at STOP, and there is only a single balise group just before the signal, the ATP system would ensure that the train was slowed before it reached the signal. If the signal clears from STOP as the train approaches, the new movement authority cannot be given until the train reaches the balise group at the signal, so the train will be travelling more slowly than necessary. For this reason, infill is provided at some signals to give new movement authorities before trains reach signals displaying a proceed indication, so allowing them to accelerate to a speed consistent with the signal indication. Obviously, if the signal remains at STOP, no new movement authority is issued.

Infill is provided by infill balise groups, Euroloops or radio-transmitted infill. These enable a new movement authority to be transmitted before a train reaches the balise group at a signal. It can be thought of as similar to the function of repeater signals. Infill balises, Euroloops and radio infill transmit the Movement Authority information of the signal balise group ahead.

Figure 8 to Figure 10 show the effects of infill on the permitted train speeds on the approach to a signal that has cleared.

Figure 8 shows the situation without infill. The train must travel quite slowly near the signal to avoid exceeding the permitted speed.

Figure 8: Approach to a signal that has cleared, with no infill



Figure 9 shows the situation with balise infill. As the train passes over the infill balise, a new movement authority is transmitted, and the train can accelerate to a speed consistent with the signal indication.

Figure 9: Approach to a signal that has cleared, with balise infill.

Figure 10 shows the situation with Euroloop infill. As soon as the signal clears, if the train is on the Euroloop, a new movement authority is transmitted, and the train can resume track speed. If the train travels onto the Euroloop after the signal had cleared, the Euroloop would immediately transmit the new movement authority.

Figure 10: Approach to a signal that has cleared, with Euroloop infill.



With radio infill the updated Movement Authority can be transmitted as soon as the related signal has cleared. It will be set up so that new Movement Authorities are not transmitted until the train has reached the sighting distance of the related signal.

Managing a train through a section The process as a train travels through several blocks in a section is depicted in Figure 11 to Figure 17.

Figure 11 shows the train approaching Signal S1, which is displaying a proceed indication. The current movement authority extends as far as signal S2.

Figure 11: Approaching a signal indicating proceed

When the train passed over the balise group (BG1) associated with signal S1, it receives a movement authority with an end of authority at signal S3, as that is as far as the signalling system can provide occupancy information, as shown in Figure 12.

Figure 12: Train receives a movement authority at BG1



Signal S2 is also displaying PROCEED. When the train passes over balise group BG2, it receives a new movement authority with an end of authority at signal S4, as shown in Figure 13.

Figure 13: Train receives a movement authority at BG2

If signal S3 remains at Caution, when the train passes over balise group BG 3, the movement authority is not extended. The end of authority remains at signal S4, as shown in Figure 14.

Figure 14: Movement authority is not extended when passing BG3

Because signal S4 remains at STOP, the Driver stops the train before it has read balise group BG4, as shown in Figure 15. If the train were to pass balise group BG4, the balise group would transmit a trip order, immediately applying the emergency brake.



Figure 15: Train stopped at signal S4, balise group BG4 has not been read

When signal S4 clears, the Driver may accelerate towards the signal.

Figure 16: Train accelerating from stop towards signal S4

When the train reads balise group BG4, it receives a new movement authority for the block ahead, as shown in Figure 17.



Figure 17: Train getting a new movement authority as it passes balise group BG4




Some RailCorp ATP system principles

Drivers will generally drive in the same manner as previously The ATP system will be overlaid on the existing signalling system. It is designed so that Drivers should generally be able to drive largely as they do currently.

Drivers will continue to be responsible for managing train speed appropriately for the conditions, and for observing and obeying fixed signals and signs, however, the ATP system provides additional risk controls against overspeeding and passing the limits of authorities.

During the initial rollout of the ATP system into the RailCorp network, temporary speed restrictions will not be controlled by the ATP system, and Drivers will be fully responsible for obeying these restrictions.

Drivers will always be fully responsible for obeying the indications given by Handsignallers, and reacting appropriately to track obstructions and other unsignalled events.

Drivers will continue to obey the rules for responding to signals and passing signals at STOP

The existing Network Rules for passing a signal at STOP must still be followed, but the DMI may provide additional information to Drivers. If there is discrepancy between the indication given by a signal, and the onboard ATP equipment, the Driver must obey the signal.

Once a Driver has passed a signal at STOP in accordance with the Network Rules, the system will impose a 25km/h maximum speed until the next signal is reached.

Different modes for different movements Travel on running lines is very different to slow speed shunting. Moving towards an obstruction such as a buffer stop or a failed train is different again. For these reasons, and others, there are a number of different modes in which the ATP onboard equipment will operate, each of which allows Drivers to perform a given selection of movements under defined speed limits.

Some of these ATP modes are automatically entered when the train passes particular balises, such as those marking the entry to the network from a siding, or those marking exit from the RailCorp network to another, unfitted network. Others can be selected by the Driver after receiving appropriate authority from the Network Control Officer or Yard Controller, such as those required to make unsignalled movements.



FAQs

How will the ATP system help RailCorp?

Safety

The requirement for RailCorp to implement an ATP system arose from the Waterfall inquiry. The system would have prevented the train from greatly exceeding track speed and derailing.

The system will also intervene to stop a train that passes a signal at STOP, unless specific administrative procedures are carried out before the train passes the signal.

Capacity

Because Drivers must see signals to react to them, many signals are placed in locations that are optimised for sighting rather than in locations that would provide the most efficient frequency of movements. In the future, the ATP system should, by providing advanced warning of stop signals ahead, allow trains to travel faster or more closely following other movements in some areas.

This improvement will not happen during the initial rollout of the system in different areas and in individual trains, but will be achievable in areas fully fitted with ATP trackside equipment when all trains travelling in those areas have been equipped.

In the future, the system has the potential to be upgraded, independently of the signalling system, so that these efficiency improvements can be maximised.

Can all Drivers operate an ATP-fitted train? During the transition period, when not all Drivers might be fully trained in using the ATP system, there will be a bypass switch that enables the onboard equipment to be bypassed such that the train will operate as if it does not have ATP equipment. All Train Crews will be trained in using the bypass switch and isolating the system. Obviously, the safety benefits of ATP will not apply while the bypass switch is active.



Will ATP prevent all SPADs? The ATP system will not prevent all SPADs, however high speed SPADs at signals protecting a nearby danger point will be prevented.

As a train approaches a signal at STOP, the ATP system will enforce braking down to a speed such that the train, if it is tripped at the signal, will not pass the overlap or danger point ahead of the signal. In areas of the RailCorp network with long overlaps, the approach speed can be near track speed, however, where there are short overlaps, the approach speed will be low.

Drivers will always be responsible for stopping their trains before signals at STOP.

NOTE: The maximum design overlap for ATP has been set at 500m so that trains will be stopped before worksites protected by signals set at STOP.

Will the DMI distract Drivers from their normal driving tasks? Because the DMI gives Drivers additional information to that which they currently get, there will be different demands on Drivers’ attention. However, the system and the layout of trackside equipment will be designed so that warnings and messages are usually given before the train closely approaches critical areas, and not while the Driver’s concentration is likely to be required for other tasks.

What if the ATP trackside equipment fails? There is usually some redundancy built in to the ATP trackside equipment. On the approaches to permanent safety-critical locations, such as signals, missing a balise group should not affect the safety provided by the system.

Much of the equipment works independently from other ATP trackside equipment, so a failure in one transponder can be safely managed by adjacent transponders, with no significant impact on safety levels.

If a significant area has defective trackside equipment, trains can be driven, after selecting the appropriate mode, using the normal signalling system, with appropriate administrative controls.

What if the ATP onboard equipment fails? If the ATP onboard equipment fails, it can be isolated, and the train can continue to operate using the existing safeworking rules and procedures, with appropriate administrative controls.

In a similar way to how existing Driver safety systems are managed, before ATP onboard equipment may be isolated, the isolation must be authorised by the Network Control Officer.



What if a signal returns to stop as a train approaches? If a signal returns to STOP in front of a closely approaching train, the balise at the signal will issue a trip order, causing an immediate emergency brake application, similar to what currently happens at signals fitted with train stops.

What will ATP-fitted trains do in areas without ATP trackside equipment?

Trains with ATP onboard equipment travelling in areas without ATP trackside equipment (known as Level 0 areas) will be run with the equipment turned on, and in Unfitted mode.

In this mode, only the maximum allowable speed for the particular train type is enforced, and Drivers will operate the trains as they do now.

What might happen in the future? RailCorp is initially planning to introduce a Level 1 ATP system, which retains the existing signalling system. The ETCS specifications allow this to be upgraded to Level 2 and then Level 3. The ATP equipment installed on trains can also be used for Levels 2 and 3.

Level 2 ATP uses conventional fixed blocks, but does not need signals (though signals can be retained). Movement authorities are not transmitted from balises on the track, but are issued by radio to the onboard equipment. A pilot scheme of Level 2 operation will be conducted following the initial rollout of Level 1 on the Cronulla branch line.

Level 3 ATP uses moving blocks. A centralised radio centre continuously manages trains according to their relative positions, speeds and braking characteristics. The distance of separation is governed by each train’s braking characteristics, so a fast-braking modern electric train could follow another movement more closely than could a hard-to-stop freight train.

Plans are being developed to test the applicability of Level 2 ATP in RailCorp’s operating environment. In the near future, it is unlikely that Level 3 could be implemented.

Conclusion As mentioned, this document is intended only as a simple introduction to the basics of an ATP system. To find out more, visit the ATP Project intranet site. The site is undergoing revision, and more information will be provided as the project progresses.

Additionally, there are a number of ATP-related websites on the internet. Google ETCS, or ERA.

http://intranet.railcorp.nsw.gov.au/Business%20Groups/Asset%20Management/Communications%20&%20Control%20Systems/ATP%20Project/index.htm

http://intranet.railcorp.nsw.gov.au/Business%20Groups/Asset%20Management/Communications%20&%20Control%20Systems/ATP%20Project/index.htm

Documents

A Brief Introduction to the RailCorp ATP System v3pt0