Proceedings 2002/2003 - IRSE

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54 SIGNALLING CONTROL CENTRES TODAY AND TOMORROW many options to choose from, and there is even a facility to embed “area specific code” to tailor the decision making to special requirements of each site. All this means that there is a significant risk of under-performance of ARS if there is insufficient understanding of the true operating requirements at the design stage. This did happen in practice, particularly in the early years, where ARS data preparation was being undertaken at a number of sites by relatively inexperienced staff. Lessons have been learned and the process is now much more robust due to: • dedicated staff undertaking all IECC data preparation work; • co-location of the data preparers with the software/system developers; • formal dialogue with operators using questionnaires and specifications; • system testing with simulated train movements to a real timetable. There is also now a much better understanding of what are the reasonable limits to flexible utilisation of the infrastructure. An example of this has been the approach to routing of trains over the 6-track bi-directional approach to Paddington station in London. As originally specified there were a large number of alternative routes available and no pre-determined rules for their selection. This was not a problem for ARS, which applied its regulation algorithms to determine the optimum choice of route for each train. However, this resulted in decisions which appeared unpredictable to signallers and drivers as ARS varied route setting decisions for the same train from day to day to achieve a few seconds of train delay savings. As part of the general review and simplification of signalling on the approaches to Paddington in the aftermath of the Ladbroke Grove accident, the timetable and ARS rules have been changed so that each train now has a preferred route and a small number of alternatives from which ARS can select. If future the application of ARS will be one of the factors to be considered when undertaking track layout risk assessments for new schemes. Another factor which has only slowly been recognised is that there is a case for more frequent updating of ARS than traditional signalling control centre systems. The traditional expectation is that an update occurs only when there are track layout changes or equipment replacement. In the case of ARS there are reasons why updates may be required more frequently: • the complexity and novelty of ARS means that there is a steady stream of ideas for minor improvements to the software; • there may be a need to make changes to deal with the evolution of traffic patterns and timetables. Funding of such changes has often been a problem, as budget allocations tend to go to projects which produce physical results, such as track remodelling, but there is a growing realisation that regular updates of a complex system such as ARS can be regarded as routine maintenance to keep the system performing at peak efficiency. This can often be justified in a business case by predicting the reduction in train delays which can be achieved – on the privatised UK railway today the conversion of train delays to money is precisely defined. Railtrack now recognises that ARS subsystems are likely to be updated more frequently that other parts of IECC, and intends to use the new CD-ROM facility to make these changes as efficiently as possible. TIMETABLE PROCESSOR As well as its fixed rules and real-time information, ARS requires timetable data including information on conditional and special workings on a daily basis. The Timetable Processor (TTP) is the IECC sub-system which provides the interface between the real-time ARS and the off-line train service database (TSDB), the Railtrack system used to create and update timetables. TTP uses the same processors as the real-time IECC sub-systems, but running the Unix operating system with a hard disc drive. The data flows between TTP, ARS and the signaller are shown in Figure 4. TTP provides a number of facilities to ensure that ARS gets a complete and correct timetable, both by checking the incoming information and making corrections and additions if necessary. Validation facilities include a check that the incoming data provides all the necessary information about each train required by ARS, and output of summary timetables showing arrivals, departures, platforming and next workings at major stations. Normally a new timetable is loaded into ARS twice a day, but there is a facility for “very short term” changes to be loaded as soon as they are entered. This allows changes such as swapping a defective train set for a healthy one at a terminus, or termination of a train short of its usual destination, to be entered into TTP and implemented via ARS without fallback on to manual route-setting. There is also a facility for a signaller to create a timetable for a train using a pre-defined “special timing pattern”. This allows the signaller to select a pre-defined route and stopping pattern for the train. TTP then calculates a complete timetable starting at the train's current location and sends it back to ARS. On one occasion when a strike was cancelled at the last minute and there was no timetable available, a complete day’s operations at one IECC were run using special timing patterns. Another facility available to the signaller is the option to invoke a contingency plan. This is a set of rules for modifications to the timetable to deal with a predefined change to the normal pattern of working. An example of this would be operating all traffic on a 4-track railway over two tracks only between selected crossovers during engineering work. The rules are pre-defined as part of the ARS data preparation process and, when a contingency plan is invoked, TTP calculates the changes to the timetable and sends them to ARS. Trains running to contingency plans or special timing patterns are distinguished on the signaller’s workstation screen
SIGNALLING CONTROL CENTRES TODAY AND TOMORROW 55 NATIONAL TRAIN SERVICE DATABASE Full timetables Daily timetable update TTP USER Timetable Summary timetables Timetable validation reports Request contingency plan Request special timing pattern TTP Main timetable Amendment timetable ARS status query Request contingency plan Request special timing pattern ARS status query Request contingency plan Request special timing pattern Train describer steps SIGNALLER Alarms ARS status Signalling Workstation Alarms ARS status TD code insert ARS Route availability Train detection Route request Figure 4: ARS data flows INTERLOCKING with an alternative background colour in the train describer berths. In a similar manner to the real-time IECC sub-systems, the original hardware used for TTP is no longer available, but there has been a straightforward upgrade path. The software is largely unchanged, but there have been a number of improvements to match upgrades to ARS, and upgrading of the train service database connection to use more modern communications technology. INTERFACING TO EXISTING RELAY INTERLOCKINGS The IECC system was designed around the use of SSI as the interlocking. Each SSI central interlocking cubicle includes a pair of panel processor modules, duplicated for availability, and these are connected by a simple serial interface to nodes of the IECC network. The IECC sub-systems use the same “state of the railway” model as SSI, so the messages from interlocking to signaller’s workstation and ARS are simply reports of updates to the states. In the opposite direction, the IECC sub-systems generate “panel requests” which are processed in the SSI to initiate route setting and other interlocking functions. All the IECC applications have been as part of major recreate-signalling projects, where most of the existing signalling has been totally replaced by new equipment including SSI. However, in some cases, there has been a desire to retain existing relay interlockings within the IECC controlled area. This need is satisfied by the Remote Interlocking Interface (RII) sub-system which allows a relay interlocking to be interfaced to IECC via a conventional time division multiplex (TDM) remote control system. To provide a cost-effective solution it is important to avoid any costly modifications to the existing relay interlocking, so the role of the RII is to appear as an SSI from the viewpoint of the other IECC sub-systems, and to appear as a conventional control/indication panel from the viewpoint of the relay interlocking. This implies that RII must implement: • a protocol translation (between the IECC network protocol based on a polling arrangement and a TDM protocol based on cyclic scans); • a functional translation to convert panel indication states into SSI-like states, and to convert SSI panel requests into switch and button sequences; • logic required to support IECC functionality which is usually provided in SSI but is not already provided in the relay interlocking (eg signallers’ reminders, ARS sub-areas, train operated route release). This functionality has been achieved by translating the SSI interlocking functional program into a high level language which allows it to run on the same Motorola 68000/VME hardware as other IECC sub-systems. The required functional translation and additional logic can then be implemented using standard SSI geographic data, which is well understood by designers and testers, and supported by the SSI Design Workstation tools. For instance indications reported from the interlocking over the TDM link are treated like input telegrams on the SSI trackside data link, and input telegram data is used to map these into the standard SSI “state of the
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Proceedings 2002 - 2003
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The Institution of Railway Signal E
Page 5 and 6: Contents Contents ……………
Page 7 and 8: 5 PETER STANLEY BSc CEng FIEE FIRSE
Page 9 and 10: OFFICERS AND COUNCIL 7 Photo: Colin
Page 11 and 12: 9 Institution Announcements (The pr
Page 13 and 14: INSTITUTION ANNOUNCEMENTS 11 Head O
Page 15 and 16: 13 Institution Awards PRESIDENT’S
Page 17 and 18: OBITUARIES 15 overseen the conversi
Page 19 and 20: 17 Annual Dinner and Dance The Inst
Page 21 and 22: 19 The Institution of Railway Signa
Page 23 and 24: PRESIDENTIAL ADDRESS 21 in terms of
Page 25 and 26: PRESIDENTIAL ADDRESS 23 technical l
Page 27 and 28: EUROBALISE TRANSMISSION SYSTEM, A T
Page 33 and 34: Company Announcement Bridgen Enterp
Page 35 and 36: EURORADIO AND THE RBC 33 another wh
Page 37 and 38: EURORADIO AND THE RBC 35 communicat
Page 39 and 40: EURORADIO AND THE RBC 37 PLAINTEXT
Page 41 and 42: EURORADIO AND THE RBC 39 4.7 DISCON
Page 43 and 44: EURORADIO AND THE RBC 41 would be a
Page 45 and 46: EUROCAB AND THE DRIVER MMI - AN INT
Page 51 and 52: 49 Technical Meeting of the Institu
Page 53 and 54: SIGNALLING CONTROL CENTRES TODAY AN
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Page 67 and 68: MIGRATION TO ERTMS ON EXISTING LINE
Page 75 and 76: CTRL SIGNALLING AND COMMUNICATIONS
Page 87 and 88: INTERNATIONAL CONVENTION 85 RIC lev
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Page 91 and 92: INTERNATIONAL CONVENTION 89 the sys
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Page 97 and 98: NINETIETH ANNUAL REPORT 95 THE INST
Page 99 and 100: NINETIETH ANNUAL REPORT 97 THE INST
Page 101 and 102: NINETIETH ANNUAL REPORT 99 Accounts
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NINETIETH ANNUAL REPORT 107 Fabbian
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112 Sydney Hosts 2002 Convention Fo
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114 SYDNEY HOSTS 2002 CONVENTION
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116 SYDNEY HOSTS 2002 CONVENTION Co
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118 Much Better Engineer Signal Eng
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120 2002 Examination Results Anothe
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THIS SPACE COULD BE WORKING FOR YOU
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124 AUSTRALASIAN SECTION dangerous
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126 AUSTRALASIAN SECTION to address
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128 CHAIRMAN’S REPORT Midland & N
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134 WESTERN SECTION Scotland. (Atte
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136 YORK SECTION The October meetin
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138 Younger Members’ Section The
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140 The Editor would like to thank
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Railway Signalling… A Science or
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