Guidance on Lineside Signals, Indicators and Layout of Signals. Rail Industry Guidance Note for GK/RT0045

Transcription

1 GN Published by Block 2 Angel Square 1 Torrens Street London EC1V 1NY Copyright 2012 Rail Safety and Standards Board Limited GK/GN0645 Issue Two: March 2012 Rail Industry Guidance Note for GK/RT0045

2 Issue record Issue Date Comments One 06 February 2010 Original document Two 03 March 2012 Replaces issue one Small scale change amendment to GK/RT0045 issue two necessitated by revision of and to permit the use of a bar of light or a line of five lunar white light points to display the indication of the route Clauses 9.1.1, 9.1.2, 9.1.3, and relating to identity of signals and indicators were removed from GK/RT0045 issue two as these were transferred to GK/RT0009 issue four which was published in June 2011 Amended or additional parts and/or sections of revised pages have been marked by a vertical black line in the adjacent margin. Superseded documents The following Railway Group documents are superseded, either in whole or in part as indicated: Superseded documents GK/GN0645, issue one, Guidance on Lineside Signals, Indicators and Layout of Signals GK/GN0645, issue one, Guidance on Lineside Signals, Indicators and Layout of Signals Sections superseded 9.1.1, 9.1.2, 9.1.3, and GN154, GN155, GN157 and GN and Date when sections are superseded 03 September June 2012 Supply GK/GN0645, issue one,, ceases to be in force and is withdrawn as of 02 June The authoritative version of this document is available at Uncontrolled copies of this document can be obtained from Communications,, Block 2, Angel Square, 1 Torrens Street, London EC1V 1NY, telephone or enquiries@rssb.co.uk. Railway Group Standards and associated documents can also be viewed at Page 2 of 179

3 Contents Section Description Page Part 1 Introduction Purpose of this document Copyright Approval and authorisation of this document 7 Part 2 Guidance on Requirements for Signalling Equipment Display of operational information using the signalling system Specification of lineside signals Specification of route indicators Specification of lineside indicators Specification of lineside signs and buffer stops used as signals 63 Part 3 Guidance on Layout of Signals: Requirements for Stop Signals Provision of stop signals and signalling indicators 70 Part 4 Guidance on Layout of Signals: Aspect Sequences Requirements for cautionary aspect sequences Requirements for banner repeating signal aspects 105 Part 5 Guidance on Layout of Signals: Junction Signalling Requirements for route indications Junction signalling: colour light signal aspect sequences Junction signalling: semaphore signal aspect sequences Junction signalling: AWS requirements Junction signalling: prohibited aspects 147 Part 6 Guidance on Layout of Signals: Bi-directional Signalling Bi-directional signalling 149 Part 7 Guidance on Layout of Signals: Combinations of Signal Aspects and Indications Combinations of signal aspects (including ERTMS level 2 operated lines) Combinations of signal aspects and route indications Signalling indications displayed in association with signal aspects 155 Part 8 Guidance on Degraded Signalling Degraded colour light signalling 157 Part 9 Application of this Document Application infrastructure managers Application railway undertakings Health and safety responsibilities 162 Appendices Appendix A Signals and Indicators: Emitted Light Parameters 163 Appendix B Signals and Indicators: Structure Requirements 165 Appendix C Signals and Indicators: Standard Performance Categories 168 Appendix D Positioning Criteria for Stop Signals on Electrified Lines 171 Definitions 175 Abbreviations and acronyms 177 References 178 Tables Table 1 Colour light signal ON and OFF aspects 14 Table 2 Banner repeating signals ON and OFF aspects 25 Page 3 of 179

4 Table 3 Independent position light signals ON and OFF aspects 27 Table 4 Subsidiary position light signals associated with a colour light signal: ON and OFF aspects 28 Table 5 Independent position light signals (limit of shunt) aspect 29 Table 6 Semaphore main stop signal ON and OFF aspects 33 Table 7 Semaphore distant signal ON and OFF aspects 36 Table 8 Semaphore subsidiary signal ON and OFF aspects 38 Table 9 Semaphore shunting signal ON and OFF aspects 40 Table 10 Position light junction indicator: displayed route indications 43 Table 11 Preliminary route indicators: displayed indications 46 Table 12 Points indicator: displayed indications 47 Table 13 Driver s level crossing indicator: displayed indications 49 Table 14 Loading / unloading indicator: displayed indications 51 Table 15 SPAD indicator: displayed indications 52 Table 16 OFF indicator: displayed indications 55 Table 17 CD and RA indicators: displayed indications 57 Table 18 BU indicators: displayed indications 58 Table 19 TPWS indications 60 Table 20 Permitted combinations of TPWS, points and/or LC indications 62 Table 21 Stop board: permitted dimensions 64 Table 22 Methods of junction signalling 125 Table 23 Speed ranges for flashing aspect sequences 128 Table 24 Permitted combinations of signal aspects 152 Table 25 Permitted combinations of signals and route indicators 154 Table 26 Permitted combinations of signals and route indicators 155 Table A.1 Colour classes for signal lights 163 Table C.1 Standard performance categories 168 Tables (Guidance) GN Table 1 Flashing green signal aspect 15 GN Table 2 Transition between 3-aspect and 4-aspect sequences 91 GN Table 3 Examples of splitting banner repeating signal aspect configurations 110 GN Table 4 Aspects displayed using the primary signal head only 138 GN Table 5 Meaning of splitting distant signal aspect combinations 139 Figures Figure 1 Figure 2 Example of a 4-aspect colour light splitting distant signal (left-hand divergence) mounted on the left-hand side of the line 20 Banner repeating signal aspect meeting standard performance category 2 24 Figure 3 Semaphore main stop signal arm 32 Figure 4 Distant signal arm 35 Figure 5 Semaphore subsidiary signal arm 37 Figure 6 Semaphore shunting signals 39 Figure 7 Figure 8 Figure 9 Position light junction indicator using five lunar white lights (example shows position 1) 41 Position light junction indicator using an LED or fibre optic cluster (example shows position 1) 41 Orientation of position light junction indications relative to diverging routes 43 Figure 10 SPAD indicator 53 Figure 11 Stop board 64 Figure 12 Distant board 66 Figure 13 Buffer beam: format and colour 68 Figure 14 Figure 15 Example of a 3-aspect to 4-aspect transition using transition method 1 92 Example of a 3-aspect to 4-aspect transition using transition method 2 93 Page 4 of 179

5 Figure 16 Figure 17 Figure 18 Example of a 3-aspect to 4-aspect transition using transition method 3 94 Semaphore junction signal: examples of main signals displaying stepped multiple semaphore arms 143 Semaphore junction signal: examples of main signals displaying stacked multiple semaphore arms 144 Figures (Guidance) GN Figure 1 A typical lineside signalling system interface 10 GN Figure 2a Examples of a vertically mounted 4-aspect colour light signal 17 GN Figure 2b Example of a horizontally mounted multiple lens 3-aspect colour light signal 18 GN Figure 3 Typical applications of position light signals 27 GN Figure 4 Typical semaphore signal aspects 35 GN Figure 5 Position light junction indicator using a bar of light with a gap between rows of light sources (example shows position 1) 42 GN Figure 6 Example of a SPAD indicator at a converging junction 54 GN Figure 7 Example of a stop signal provided for a reversing move 72 GN Figure 8 Example of an intermediate block home signal beyond the signal box 80 GN Figure 9 Example of a loading / unloading indicator application 82 GN Figure 10 Example of a 3-aspect to 4-aspect transition at a diverging junction 90 GN Figure 11 Example of a 4-aspect to 3-aspect transition on plain line 95 GN Figure 12 Example of a 4-aspect to 3-aspect transition at a diverging junction 96 GN Figure 13 Example layout showing separate semaphore stop and distant signals 98 GN Figure 14 GN Figure 15 GN Figure 16 GN Figure 17 Example of a colour light distant signal reading towards a semaphore stop signal 99 Example of a 4-aspect sequence approaching a semaphore stop signal 100 Example of a red / green colour light section signal reading towards a semaphore distant signal 100 Example of 3-aspect starting signals leading up to a 4-aspect sequence 101 GN Figure 18 Example of a stop board on a diverging route 103 GN Figure 19 Example of a 2-state banner repeating signal application 106 GN Figure 20 Example of a 3-state banner repeating signal application 107 GN Figure 21 Single head banner repeating signal associated with a junction signal 108 GN Figure 22 Splitting banner repeating signal associated with a junction signal 109 GN Figure 23 GN Figure 24 GN Figure 25 Splitting banner repeating signal where there is no obvious straight ahead route 109 Example of a junction signal where there is no geographically obvious straight ahead route 115 Example of a junction signal where the straightest route through the junction is an un-signalled route 116 GN Figure 26 Example of a junction signal where the diverging route crosses over 116 GN Figure 27 Preliminary route indicator typical normal arrangement 123 GN Figure 28 Preliminary route indicator typical alternative arrangement 123 GN Figure 29 Example of junction method 1: unrestricted aspect sequence 126 GN Figure 30 Example of junction method 1 applied for a converging route 127 GN Figure 31 Example of junction method 2 using a 4-aspect flashing aspect sequence 128 GN Figure 32 Example of junction method 3 using a 4-aspect sequence 132 GN Figure 33 Example of junction method 4: approach control from yellow 134 GN Figure 34 Example of junction method 5: splitting distant aspect sequence 137 GN Figure 35 GN Figure 36 GN Figure 37 Example of a 4-aspect splitting distant signal on the left-hand side of the line when the junction is set for a left-hand divergence 139 Example of a 4-aspect splitting distant signal on the left-hand side of the line when the junction is set for a right-hand divergence 139 Example of a 4-aspect splitting distant signal on the left-hand side of the line when the junction is set for a straight ahead route at a left-hand junction 139 Page 5 of 179

6 GN Figure 38 Example of a 4-aspect splitting distant signal on the left-hand side of the line when the junction is set for a straight ahead route at a right-hand junction 140 GN Figure 39 Example of a flashing aspect displayed by a splitting distant signal 141 GN Figure 40 Example of semaphore junction signalling 145 GN Figure 41 Example of semaphore junction signalling with a splitting distant signal 146 GN Figure 42 Example of reduced capacity bi-directional signalling 150 GN Figure 43 Example of 3-aspect signals provided for the contraflow direction 151 Page 6 of 179

7 Part 1 Introduction 1.1 Purpose of this document This document gives guidance on interpreting the requirements of Railway Group Standard GK/RT0045, issue two, Lineside Signals, Indicators and Layout of Signals. It does not constitute a recommended method of meeting any set of mandatory requirements. Relevant requirements in GK/RT0045 are reproduced in the sections that follow. Guidance is provided as a series of sequentially numbered clauses prefixed GN immediately below the text to which it relates. Where there is no guidance given, this is stated. Specific responsibilities and compliance requirements are laid down in the Railway Group Standard itself. This document contains requirements that are amended under the Railway Group Standards Code (Issue Three) as a small scale change. Reference to the amended requirements is made in the Issue record. All other parts of the document are unchanged from the previous issue. 1.2 Copyright Copyright in the Railway Group documents is owned by Rail Safety and Standards Board Limited. All rights are hereby reserved. No Railway Group document (in whole or in part) may be reproduced, stored in a retrieval system, or transmitted, in any form or means, without the prior written permission of Rail Safety and Standards Board Limited, or as expressly permitted by law. Rail Safety and Standards Board () members are granted copyright licence in accordance with the Constitution Agreement relating to Rail Safety and Standards Board Limited. In circumstances where Rail Safety and Standards Board Limited has granted a particular person or organisation permission to copy extracts from Railway Group documents, Rail Safety and Standards Board Limited accepts no responsibility for, nor any liability in connection with, the use of such extracts, or any claims arising therefrom. This disclaimer applies to all forms of media in which extracts from Railway Group Standards may be reproduced. 1.3 Approval and authorisation of this document The content of this document was approved by Control Command and Signalling (CCS) Standards Committee on 15 December This document was authorised by on 19 January Page 7 of 179

8 Part 1 Purpose and Introduction 1.1 Purpose The purpose of this document is to specify the parameters and application of lineside signalling equipment that is used to display information about movement authorities, equipment status and required operations to infrastructure managers at stations and railway undertaking personnel. This document mandates the requirements for: a) The format and presentation of signals and their displayed aspects. b) The format and presentation of indicators and their displayed indications. c) The permitted combinations of signals and indicators. d) The criteria for positioning signals within the layout. e) The permitted type(s) of lineside signal and their application constraints. f) The permitted sequences of signal aspects and indications displayed to drivers. g) The forms of signal identification necessary to support communication of safety related operational messages between train crew and signallers Parts 2, 3, 4, 5, 6, 7, 8 and 9 of this document are applicable to areas where train movements are controlled using lineside signalling Parts 2, 4 and 7 of this document include some requirements (set out in 2.4.5, and 7.1) applicable to areas where train movements are controlled using the European Rail Traffic Management System (ERTMS) Level 2 without lineside signals. Where this is the case, the particular applicability to ERTMS is described in the section heading and the applicable clause(s). 1.2 Introduction Background Lineside signals and indicators are provided by the infrastructure manager where it is necessary to display information about movement authorities, equipment status and / or required operations to railway undertaking personnel, including train crew (for example, drivers, shunters and guards) and station staff (for example, train dispatchers) Movement authority information displayed by lineside signalling equipment includes information about: a) The extent of the movement authority issued by the signaller or ground frame operator (depicted by the sequence of signal aspects), and b) The route that is set and the destination (depicted by combinations of signal aspects and route indications) At some locations, movement authority information is supplemented by additional information relating to the train operation, typically: a) Infrastructure equipment status (for example, locally monitored level crossings), and b) Operational information (for example, Close doors ) Railway undertaking personnel are able to: a) Understand the operational rules that are associated with the aspects and indications displayed by signalling equipment. Page 8 of 179

9 b) Understand the movement authorities issued by the infrastructure manager using: i) The sequence of displayed signal aspects and indications. ii) iii) Knowledge of the route and the geographical location. Knowledge of the required train movement Principles c) Control the movement of trains within the limits of the movement authority. d) Identify and report signal aspect and indication irregularities This document provides for infrastructure managers and railway undertakings compatibility in terms of understanding the information conveyed by signal aspects and indications. Incompatibility is a causal factor of an operational irregularity such as a signal passed at danger (SPAD) The GE/RT8000 Rule Book sets out: a) The operational meaning of signal aspects and indications displayed by the infrastructure manager. b) The rules for train driving, which include the requirement to control the speed of the train with respect to the aspects and indications displayed by signals. c) The rules for shunting. d) The rules for train dispatch. e) The rules for reporting signalling system failures The lineside signalling equipment is compatible with the operating rules, so that operating personnel can correctly interpret the information displayed by the signalling system The standard performance requirements applicable to lineside signals and indicators are specified, so that displayed aspects and indications are visible to the driver The layout of signalling equipment is specified so that, when train movements take place, drivers are given sufficient and appropriate movement authority information Related requirements in other documents The following Railway Group Standards contain requirements that are relevant to the scope of this document: GC/RT5021 GE/RT8000 GE/RT8030 GE/RT8035 GE/RT8037 GE/RT8071 GK/RT0075 GK/RT0044 GO/RT3215 Track System Requirements Rule Book Requirements for a Train Protection and Warning System (TPWS) Automatic Warning System Signal Positioning and Visibility Control Facilities for use during Lineside Signalling Failures Lineside Signal Spacing and Speed Signage Controls for Signalling a Train onto an Occupied Line Requirements for the Weekly Operating Notice, Periodical Operating Notice and Sectional Appendix Supporting documents GK/GN0645. Page 9 of 179

10 Part 2 Guidance on Requirements for Signalling Equipment 2.1 Display of operational information using the signalling system GN01 Section 2.1 sets out the requirements for displaying operational information to train operators using the signalling equipment specified in this standard. GN02 The permitted types and parameters of displayed operational information are described in Section 2. The GE/RT8000 Rule Book sets out how train operators respond to the displayed information, which includes: a) Movement authority information, using signals and route indicators. b) Equipment status information, using lineside indicators (for example, Points set ). c) Operational information, using lineside indicators (for example, Right away ). GN03 Where a project proposes to display operational information using a non-compliant type of equipment, or to convey the information using a different format or sequence of signal aspects or indications, or to display different information: a) A temporary non-compliance against GK/RT0045 should be obtained before the proposed arrangements are tested on the operational railway, and b) Following successful trials, a proposal for standards change should be submitted to amend GK/RT0045 to incorporate the new arrangements. GN04 Where a lineside signalling system (as opposed to cab signalling or verbal authority) is used to display operational information, interfaces arise between the lineside signalling equipment (infrastructure manager) and the train operator (railway undertaking). Understanding of the operational information is a property that arises at these interfaces (see GN Figure 1). Aspect / indication Train driver s eye AB 6 Understanding the operational information G GN Figure 1 A typical lineside signalling system interface GN05 Operational information displayed by the signalling system is typically used by: a) Drivers, when train movements are required. b) Guards and station staff, during train dispatch operations. c) Shunters, during shunting operations. GN06 Movement authority information displayed by the signalling system is typically used by drivers to determine: a) The distance to the end of the movement authority, using the signal aspect. Page 10 of 179

11 b) The route set at a junction (and hence the speed reduction required) using route indications. c) The type and validity of the movement which is authorised, either non-permissive (main aspect) where the route is clear to the destination, or permissive (subsidiary aspect) where the route may be occupied or obstructed and drivers should proceed at a speed enabling them to stop short of a train. GN07 GN08 GN09 Correct understanding of the displayed operational information is necessary to support safe railway operations, but this can only be achieved if the infrastructure manager and railway undertaking are compatible at the operational interface. Because incorrect understanding of the operational information by a driver may result in an incident (for example, a SPAD), it is a causal factor in the chain of events that may lead to a train collision or derailment. Incorrect understanding may arise if there is loss of compatibility at the operational interface. This could be manifested in various ways, including: a) The signal aspect is not seen or recognised by a driver. b) The driver thinks that a main movement authority has been issued when a calling-on aspect is displayed. c) The driver thinks a straight ahead route is set when a diverging route is set at a junction. d) The driver does not have sufficient reading time approaching a signal. e) The driver thinks that a less restrictive signal aspect is being displayed. GN10 The level of risk arising from incorrect understanding depends upon the operational situation, for example: a) The type of train movement (for example, running move, shunting, permissive, propelling). b) The scope of the movement authority. c) The status of the infrastructure. d) The signalling layout. e) Other train movements. f) The local environment. g) The ambient conditions. GN11 The infrastructure manager contributes to compatibility at the operational interface by: a) Displaying visible and readable signal aspects and indications. b) Displaying signal aspects and route indications in logical and consistent sequences. c) Displaying signal aspects and indications at fixed locations. d) Identifying signals in a consistent and logical manner. Page 11 of 179

12 GN12 Railway undertakings contribute to compatibility at the operational interface by providing competent and fit personnel. Driver competence and fitness includes: a) Route specific competence, including displayed aspect sequences and indications. b) Operational competence, including the required train movements. c) Driving competence, including traction specific and condition specific driving skills. d) Rule Book competence, including the meanings of signal aspects and aspect sequences. e) Complying with driver s eyesight and health requirements. GN13 The requirements set out in GK/RT0045 apply only to the infrastructure manager, and contribute to control of the shared risk: incorrect understanding of a signalled movement authority. The measures include design parameters for: a) Signal and indicator equipment. b) Sequences of displayed signal aspects and indications. c) Equipment identification. GN14 The infrastructure manager safety management system should include procedures to manage each lineside signalling system. The safety management system should address the complete signalling system life cycle, including: a) Specification and procurement of signals and indicators. b) Safety design, including layout risk assessment and compatibility with train operations. c) Application design, including layout and control of signals and indicators. d) Signal position and visibility. e) Installation. f) Testing and commissioning. g) Operations. h) Maintenance and renewals. GN15 GN16 The assessment of compatibility for new signalling layouts and changes to existing signalling layouts should use the process for co-operation set out in GE/RT8270. The measures set out in GK/RT0045 represent existing good practice and do not represent a complete set of system requirements. The Strategy for Standards Management requires that only those safety measures requiring co-operation between duty holders need to be mandated Signalled movement authorities shall: a) Be displayed only by the lineside signals and route indicators set out in this standard (see 2.2, 2.3 and 2.5) except where lineside operational signs are used to display information about movement authorities in accordance with GK/RT0055, and b) Be displayed only using the sequences and combinations of signal aspects and indications set out in this standard (see Parts 3, 4, 5, 6, 7 and 8) Signalling indications shall be displayed only by the lineside indicators set out in this standard (see 2.4). Page 12 of 179

13 GN17 GN18 GN19 GN20 GN21 Sections 2.2, 2.3, 2.4 and 2.5 set out the requirements for lineside signalling equipment. Non-compliant signalling equipment should only be proposed if the project can demonstrate that the information displayed will be visible and readable (see Appendix C) and will be correctly interpreted by drivers. GK/GN0655 sets out further guidance about the requirements for lineside signals and lineside operational signs for different types of block systems. The requirements for stop signals in Part 3 provide the signaller with the means to control train movements towards infrastructure hazards. The aspect sequences set out in Part 4 provide the driver with information about the extent of movement authority and sufficient warning of the end of movement authority. This is necessary because, in most cases, trains travelling at permissible speeds cannot be stopped within the distance visible to drivers. In an emergency, the signaller may normalise a stop signal after a train has passed the first signal in the cautionary aspect sequence (see GE/RT8000 Rule Book). In this case, the driver would not observe the required cautionary aspect sequence (see Part 4) and assume that an emergency stop is required, although a SPAD event may occur. The permitted methods for junction signalling set out in Part 5 provide the driver with information about the route set at the junction. Other junction aspect sequences should not be used. Research into alternative methods of junction signalling may result in different methods being developed in the future: a) T274: Human centred junction signalling. b) T669: Driver s response to junction signalling: A simulator study. GN22 GN23 GN24 GN25 The signalling system should be designed to display signal aspects that are logical and that provide adequate warning of an end of movement authority. Part 6 sets out the arrangements for bi-directional signalling, in particular the requirement for provision of parallel signals so that drivers do not misread signal aspects. Part 7 sets out the permitted combinations of signal aspects and indications. Other combinations of displayed signal aspects and indications should not be used because the information displayed may be incompatible with the required train movement. The signalling system should be designed to control the operational risk that arises when signal and indicator equipment could display non-compliant signal aspects and / or indications that could mislead drivers during failure. Part 8 sets out guidance on how to address this risk The observed colour of light emitted by lineside signals and indicators shall comply with specified parameters (see Appendix A) Lineside signal and indicator structures shall comply with specified parameters (see Appendix B). GN26 The parameters set out in Appendices A, B and C provide for visibility and readability of signal aspects and indications Lineside signals shall be identified (see Part 9). GN27 The requirements for signal identification (numbering) in Part 9 support communication between train crew and the signaller, particularly when the geographical position of the train needs to be identified. Page 13 of 179

14 2.2 Specification of lineside signals Colour light signal GN28 Colour light signals are used to display non-permissive movement authorities (that is to say, when the route ahead is clear) Colour light signals shall display the ON and OFF signal aspects set out in Table 1. Signal aspect (see Appendix A) Description MA information Remarks One signal red light RED End of MA For application requirements see 3.1 One signal yellow light SINGLE YELLOW End of MA ahead For application requirements see 4.1 Two signal yellow lights displayed vertically DOUBLE YELLOW Approaching end of MA For application requirements see 4.1 One signal yellow flashing light FLASHING SINGLE YELLOW Diverging route set at next signal For application requirements see Two signal yellow flashing lights displayed vertically FLASHING DOUBLE YELLOW Approaching a diverging junction For application requirements see One signal green light GREEN Line clear Table 1 Colour light signal ON and OFF aspects GN29 GN30 GN31 The aspects in Table 1 are compatible with the operational rules for colour light signal aspects in the GE/RT8000 Rule Book. Failure to properly display one of these aspects is regarded as a signalling system failure. In some circumstances, colour light signals are combined with other signal types and indicators within the signalling layout, for example at a junction signal. The permitted combinations are set out in Part 7. A flashing green colour light signal aspect may be displayed on a section of the East Coast Main Line between Grantham and Peterborough. This signal aspect was provided in connection with >125 mph trial operations and is only displayed when the next signal is displaying a green aspect. This aspect sequence should not be displayed at any other location. Page 14 of 179

15 Signal aspect Description MA information One flashing signal green light FLASHING GREEN Line clear GN Table 1 Flashing green signal aspect Colour light signals shall display the relevant signal aspect at all times, except: a) For those signals that are configured as approach lit signals (see 4.1.8), and b) Where the signalling technology used incorporates self-testing functionality that requires a brief interruption of the displayed aspect at defined intervals, in which case each interruption shall not exceed 250 ms. GN32 GN33 The redundancy management software within SSI periodically tests that the signal module can control its power disabling relays. This is known as a Power Disable Test (PDT). A PDT takes place approximately every five hours or on an output change after more than one hour since the previous PDT. The PDT may cause a visible aspect blink of about 200 ms duration, which should be reported by drivers as an aspect anomaly. The observed aspect blink can be exacerbated when LED-type signals are used, as these react more quickly than incandescent bulbs. This problem was largely overcome by an upgrade to the SSI signal module, whereby the PDT takes place when the signal is changing aspect and is not visible to drivers. However, there can still be problems when one signal module drives two signals or where highpowered AWS is energised as a train approaches (to save power). These problems should be considered as part of the signalling system design work Except for splitting distant signals (see 2.2.2) and co-acting signals (see 2.2.3): a) Each colour light signal shall display only one signal aspect at a time, and b) No other combination of colour light signal lights shall be displayed by colour light signals. GN34 GN35 GN36 GN37 The number of signal lights contained in each signal head is dictated by the signal aspects to be displayed and the signal equipment technology used. Signal heads that display aspects by means of separate filament lamps, in combination with separate coloured lenses, can incorporate up to four signal lights surrounded by a backboard. Signal heads that display aspects by means of light-emitting diode (LED) arrays, typically incorporate one signal light at a 1-, 2- or 3-aspect signal, or two signal lights at a signal that displays a 4-aspect sequence. Signals that display red aspects should be configured so that the red light is positioned closest to the driver s line of sight. Ground-mounted signals should maintain the red light as close as practicable to the driver s eye, while maintaining the spacing between the two yellow lights. Page 15 of 179

16 Colour light signal lights that are designed to flash shall comply with the following criteria: a) Flash at a frequency of 60 (+/-10) cycles per minute. b) Have a mark:space ratio that provides visibility of the signal light for 50% - 66% of each flashing cycle when observed in accordance with the relevant standard performance category (see Appendix C). c) Flash in synchronism within the signal head when the flashing double yellow aspect is displayed. d) Flash in synchronism throughout the primary and co-acting signal heads when flashing aspects are displayed by co-acting signals Each colour light signal light shall have an apparent light source that: a) Has a diameter of 210 mm (-10mm/+20mm), and b) Meets the colour requirements set out in Appendix A Where the colour light signal head incorporates multiple signal light sources (for example, to display a double yellow aspect), the two illuminated signal light apertures shall be vertically aligned with a centre to centre separation of 510 (+20/-10 mm) Except where signal sighting can be consistently achieved without a backboard (for example, where a signal is positioned in a dark environment), a backboard shall be provided with each colour light signal (see Appendix C) Where the backboard is incorporated into the signal head, it shall have the following dimensions: a) 300 mm (minimum) from the centre of the top signal light aperture to the top edge of the signal backboard. b) 300 mm (minimum) from the centre of the signal light aperture to the left and right side edges of the signal backboard. c) 180 mm (minimum) from the centre of the bottom signal light aperture to the bottom edge of the signal backboard Where a separate backboard is provided behind the signal head, it shall be of sufficient size to appear no smaller than a signal head mounted backboard. GN38 The physical parameters of colour light signals set out in are specified so that displayed signal aspects are consistent, distinct and readable during train operations. Parameters include: a) The colour of each signal light (Table 1) (see also Appendix A). b) The number and alignment of lights to be displayed for each signal aspect (Table 1). c) The flashing rate, which is specified so that drivers have the opportunity to observe a sufficient number of flashes within the minimum reading time on the approach to the signal. A minimum of 50 flashing cycles per minute means a flash cycle length of 1.2 seconds. Therefore in 8 seconds reading, the driver will see = 6.6 flashes. d) The synchronism of signal aspects that are designed to flash, so that drivers observe flashing aspects that display multiple flashing signal lights at the same time and markspace ratio. This includes synchronism between primary and co-acting signal heads, Page 16 of 179

17 where flashing aspects are displayed by co-acting signals. It is not necessary to provide signal light synchronism between adjacent signals or consecutive signals that display a flashing aspect sequence. e) The separation distance between simultaneously displayed signal lights, so that each separate light can be clearly distinguished by the driver at the required readability distance (800 m for a long-range signal). f) The dimensions and colour of the signal lights and backboard (GN Figures 2a and 2b) (see also Appendix B) so that signal lights are visible when viewed against an illuminated background. g) The orientation of the signal head (GN Figures 2a and 2b). Vertically aligned signal heads should be used wherever practicable. Horizontally aligned signal heads can be used where signal sighting is constrained or where there is limited clearance, typically at stations. h) The standard performance category for the signal (see also Appendix C). GN39 Typical conventions for the arrangement of signal lights within an elevated signal head that provide for these requirements are shown in GN Figures 2a and 2b. 300 min 300 min 300 min 300 min SIGNAL LIGHT APERTURE POSITION 300 min / / / / (-10 / +20) 180 min 180 min SIGNAL BACKBOARD (BLACK) 4-aspect multiple lens signal 4-aspect searchlight signal All dimensions are in millimetres GN Figure 2a Examples of a vertically mounted 4-aspect colour light signal Page 17 of 179

18 SIGNAL LIGHT APERTURE POSITION 200 min 300 min SIGNAL BACKBOARD (BLACK) 300 min 180 min / / min All dimensions are in millimetres GN Figure 2b Example of a horizontally mounted multiple lens 3-aspect colour light signal Long-range colour light signals shall comply with standard performance category 1 (see Appendix C) Short-range colour light signals shall comply with standard performance category 2 (see Appendix C). GN40 GN41 Standard performance category 1 colour light signals (sometimes known as long-range colour light signals) should be used wherever possible. This is because the category 1 performance provides optimum visibility of the displayed signal aspects. Standard performance category 2 colour light signals (sometimes known as short-range or spread lens colour light signals) should only be used by exception and only at locations where train operations are compatible with category 2 signal visibility and readability parameters. Performance category 2 signals are typically provided, either: a) At locations where sharp curvature means that signal sighting requires the provision of a signal with a spread light lens to support signal sighting on the approach. Spread light lens signals do not meet performance category 1, or b) At the exit of loop lines and sidings where trains start from rest, where provision of a signal with lower performance can avoid signal sighting problems where a parallel signal is not provided on the adjacent running line Colour light signal configured as a splitting distant signal The application requirements for splitting distant signals are set out in GN42 Splitting distant signals are one of the five methods used to display advance information to drivers about the route set at a diverging junction (see 5.2.6). Splitting distant signals display this information using various combinations of horizontally and vertically arranged signal lights displayed by the two signal heads. Page 18 of 179

19 GN43 Drivers use the movement authority information displayed by splitting distant signal aspects when controlling the speed of the train so that the diverging junction is traversed at an optimum safe speed Splitting distant signals shall incorporate two colour light signal heads (see 2.2.1), referred to as the primary head and the offset head. GN44 Splitting distant signals incorporate two separate colour light signal heads (see also ), which are referred to as: a) The primary head, which describes the signal head that is positioned closest to the driver s line of sight and therefore displays the red aspect and cautionary aspects when a non-splitting signal aspect sequence is being displayed, and b) The offset head, which is located to the side of the primary head and only illuminates when a splitting distant aspect is being displayed. GN45 In the case of splitting distant signals positioned above the structure gauge (for example, on a gantry), the arrangement is dependent upon which side of the track centre-line the centreline of the two heads is positioned The primary head and offset head shall: a) Be mounted so that the horizontal separation between signal light centres in the two signal heads is 600 mm 900 mm, and GN46 The 600 mm horizontal dimension is specified so that drivers can read the combination of primary and offset signal lights at the 800 m sighting distance (see Appendix C). The 600 mm minimum dimension should only be used by exception, either: a) Where it is necessary to position splitting distant signals in areas of limited clearance, or b) To optimise signal sighting. GN47 It is good practice, where possible, to provide up to 900 mm separation between the primary and offset signal heads. The 900 mm maximum separation is specified so that the primary and offset signal heads do not look like two separate signal aspects. b) Be positioned and aligned so that horizontally displayed signal lights appear level to the train driver (see example in Figure 1). GN48 The primary and offset signal heads should be aligned so far as is practicable so that signal lights displayed in a horizontal level relationship appear horizontal to the driver of an approaching train. Drivers of tilting trains have to make allowances when trains tilt. The signal sighting committee should take account of the following when deciding how the signal heads should be positioned and aligned to achieve this: a) The dynamic effect of line curvature and cant on the approach to the signal, and b) The physical construction of the signal. Page 19 of 179

20 The splitting distant signal shall be positioned so that the primary head is located as near as practicable to the driver s line of sight, that is to say: a) For signals mounted on the left-hand side of the line, the primary head shall be mounted to the right-hand side of the offset head (see example in Figure 1), and b) For signals mounted on the right-hand side of the line, the primary head shall be mounted to the left-hand side of the offset head. Y PRIMARY HEAD OFFSET HEAD Y Y In 4-aspect areas, the top yellow light in the offset head should appear horizontally aligned with the bottom yellow light in the primary head All dimensions are in millimetres Figure 1 Example of a 4-aspect colour light splitting distant signal (left-hand divergence) mounted on the left-hand side of the line GN49 The primary head is always positioned closest to the track so that the critical information is seen by the driver. This means that the offset head is mounted on: a) The left-hand side of the primary head for signals positioned on the left-hand side of the line, and b) The right-hand side of the primary head for signals positioned on the right-hand side of the line. GN50 For the same reason, where the splitting distant signal is also a junction signal, the route indicator should always be positioned in conjunction with the primary signal head Splitting distant colour light signals shall comply with standard performance category 1 (see Appendix C). GN51 Performance category 1 colour light signals (usually known as long-range colour light signals) are used for splitting distant applications. This is because the category 1 performance provides optimum visibility of the displayed splitting distant signal aspects, which are usually associated with high-speed junctions Co-acting signals (colour light signal and semaphore signal) GN52 Typically, co-acting signals are provided where a combination of infrastructure layout and physical environment means that it is not possible to provide the required signal visibility and readability using just one displayed signal aspect. Page 20 of 179

21 GN53 Co-acting signals may be provided using either colour light signal equipment or semaphore signal equipment as long as the same form of signal aspect is displayed by the primary and co-acting parts of the signal Co-acting signals shall incorporate: a) Primary signal and, where relevant, route indicator equipment that is positioned to provide the required long-distance signal sighting and readability, as set out in GE/RT8037, and b) Co-acting signal and route indicator equipment that displays the same form (that is to say, colour light or semaphore) of signal aspect and route indication as the primary equipment, and positioned to provide the required close-up signal sighting and readability, as set out in GE/RT8037. GN54 A colour light co-acting signal comprises two colour light signal heads that are individually sighted and operated by the same electrical controls arranged as follows: a) The primary head is positioned to provide the driver with optimum long-distance signal sighting, and b) The co-acting head is positioned longitudinally within 2 m of the primary head but in a different horizontal and / or vertical position relative to the driver, to provide optimum close-up viewing. GN55 GN56 A semaphore co-acting signal incorporates duplicated signal arms, usually mounted on the same signal post, one above the other, and mechanically connected so that they work in unison. The requirement to provide a co-acting signal and the actual position of the primary and coacting parts of the signal should be determined in accordance with GE/RT8037. This should address the requirement for continuity of readability between the primary and co-acting signals The primary and co-acting signal and route indicator equipment shall meet the same standard performance requirements (see Appendix C), except where there is insufficient space to provide compatible equipment, in which case: a) The primary signal and route indicator equipment shall meet the appropriate standard performance requirement compatible with the long-distance signal sighting and readability, and b) The co-acting signal head and route indicator equipment shall meet the standard performance requirement that is appropriate for close-up signal sighting and readability. GN57 GN58 Except where local operating conditions require provision of different equipment types, the co-acting part of the signal should display aspects and indications using signalling equipment that meets the same performance category as the associated primary signal. This is to provide consistent levels of signal aspect visibility for drivers. By exception, the co-acting part of the signal may use equipment that has a lower standard performance category (see Appendix C), on the basis that the co-acting signal only needs to be readable within the constraints of the lower performance category. For example, a coacting signal may be provided at the exit of a terminal platform using a different type of signal Page 21 of 179

22 head in order to display the signal aspect to the driver when the driving cab is immediately adjacent to the signal The same main signal aspect and route indication shall be displayed by the primary and co-acting signals at all times. GN59 Co-acting signals should always repeat all of the main signal aspects and associated route indications because: a) Drivers use both the primary signal and the co-acting signal to read the signal aspect throughout the approach to the signal, and b) The GE/RT8000 Rule Book requires drivers to recognise and report signalling irregularities to the signaller, including when incorrectly displayed or corrupted signal aspects are observed. GN60 GN61 The arrangement of signal lights within a colour light signal co-acting head may be different from the primary head (for example, where the co-acting head is ground-mounted, the red aspect should be positioned closest to the driver s line of sight). An AWS clear indication should only be given when both the primary and co-acting signals are showing the correct aspect The same subsidiary / shunting aspect and route indication shall be displayed by the primary and co-acting signals at all times, except at signals where subsidiary / shunting aspects and route indications are omitted from the primary signal Subsidiary / shunting signal aspects and route indications shall only be omitted from the primary signal if the co-acting signal equipment, on its own, provides the required sighting and readability for these aspects. GN62 It is not necessary for the primary signal to display the subsidiary and shunting aspects if the co-acting signal on its own provides the required signal sighting for these aspects. In many cases, the available sighting of the primary signal may be incompatible with the category 3 standard performance requirements of the subsidiary / shunting signal aspects (see Appendix C) Signals shall only display movement authorities towards co-acting signals when both the primary and co-acting signals are detected to be displaying the correct signal aspect, except when a failure of the second yellow light of a double yellow aspect in either the primary signal or co-acting signal means results in one signal displaying a more restrictive single yellow aspect in error. GN63 If either the primary or the co-acting part of the signal fails to display the correct aspect, the previous signal should display a stop aspect because there is a possibility that the co-acting signal may not be readable. The one exception is where the top yellow of a double yellow aspect has failed in one of the signal heads. In this case the driver will observe a more restrictive aspect in one of the signal heads. However, it is preferable to allow a signalled train movement than resort to degraded operations. Page 22 of 179