Provision of Lineside Signals - RSSB Iss 2.pdf · 3 Criteria for the selection of method of...

This document is the property of Railway Safety. It shall not be reproduced in whole or in part without the written permission of the Controller, Railway Group Standards, Railway Safety. Published by: Railway Safety Evergreen House 160 Euston Road London NW1 2DX © Copyright 2002 Railway Safety

Railway Group Standard GK/RT0032 Issue Two Date February 2002

Provision of Lineside Signals

Synopsis This document defines the mandatory requirements for the provision of lineside signals and the sequences in which signal aspects shall be presented to train drivers, in respect of plain line, diverging junctions and for bi-directional lines.

Signatures removed from electronic version

Submitted by Paul Woolford Project Manager

Authorised by Brian Alston Controller, Railway Group Standards

Document to be Withdrawn as of 03/04/2010 To be Superseded by GKRT0045 Iss 1 Published on 06/02/2010

Uncontrolled When Printed

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Railway Group Standard GK/RT0032 Issue Two Date February 2002 Page 1 of 36

Contents Section Description Page

Part A

A1 Issue record 2 A2 Implementation of this document 2 A3 Scope of Railway Group Standards 2 A4 Responsibilities 3 A5 Health and safety responsibilities 3 A6 Technical content 3 A7 Supply 3

Part B

B1 Purpose 5 B2 Application of this document 5 B3 Definitions 6 B4 Principles 7 B5 Provision of stop signals 7 B6 Constraints on positioning of stop signals 9 B7 Designation of main signals 12 B8 Aspect sequences 13 B9 Aspect sequence transitions 17 B10 Junction signalling 19 B11 Bi-directional signalling 24 B12 Identity of signals 24

Appendices

1 Transition from three to four aspect signalling 27 2 Interface with London Underground lineside signalling 29 3 Criteria for the selection of method of junction control 30 (colour light signalling) 4 Colour light splitting distant signals: Permissible arrangement of aspects 32

References 35




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Part A A1 Issue Record

This document will be updated when necessary by distribution of a complete replacement.

Issue Date Comments 1 October 1995 Original Document 2 February 2002 Replaces Issue 1

Supersedes RGS as shown in section A2

Issue 2 of this standard has been subject to extensive re-writing and therefore no amendment bars have been inserted.

A2 Implementation of this document

The publication date of this document is February 2002.

This document comes into force on 6 April 2002. The dates by which compliance with the requirements of this document is to be achieved are set out in Part B2. Where those dates are later than the date on which this document comes into force, this is to give Railway Group members additional time to plan and commence implementation so as to achieve full compliance by the dates set out in Part B2.

This document supersedes the following Railway Group Standards, either in whole or in part as indicated:

Railway Group Standard

Issue No.

Title RGS sections superseded GK/RT0032 issue 2

Date as of which sections are superseded

GK/RT0009

1 Identification of Signalling and Related Equipment

Section 10

6 April 2002

GK/RT0031 3 Lineside Signals and Indicators

Section 5.2.2 (part)

6 April 2002

GK/RT0032 1 Lineside Signal aspect Sequences

All 6 April 2002

GK/RT0035 2 Layout of Lineside Signals

Sections 5, 8, 9, 10

6 April 2002

GK/RT0031 Issue 3, GK/RT0032 Issue 1 and GK/RT0035 Issue 2 are withdrawn with effect from 6 April 2002.

A3 Scope of Railway Group Standards

The overall scope of Railway Group Standards is set out in Appendix A of GA/RT6001. The specific scope of this document is set out in Part B2.




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A4 Responsibilities Railway Group Standards are mandatory on all members of the Railway Group* and apply to all relevant activities that fall into the scope of each individual’s Railway Safety Case. If any of those activities are performed by a contractor, the contractor’s obligation in respect of Railway Group Standards is determined by the terms of the contract between the respective parties. Where a contractor is a duty holder of a Railway Safety Case then Railway Group Standards apply directly to the activities described in the Safety Case.

* The Railway Group comprises Railtrack PLC, Railway Safety, and the train and station operators who hold railway safety cases for operation on or related to infrastructure controlled by Railtrack PLC.

Railtrack PLC is known as Railtrack.

A5 Health and safety responsibilities

In issuing this document, Railway Safety makes no warranties, express or implied, that compliance with all or any documents published by Railway Safety is sufficient on its own to ensure safe systems of work or operation. Each user is reminded of its own responsibilities to ensure health and safety at work and its individual duties under health and safety legislation.

A6 Technical content The technical content of this document has been approved by:

Jeff Allan, Principal S&T Engineer, Railway Safety

Richard Evans, Principal, Operations, Railway Safety

Peter Williment, Principal, Electrification, Railway Safety

Enquiries should be directed to Railway Safety – Tel: 020 7904 7518

A7 Supply Controlled and uncontrolled copies of this document may be obtained from the Industry Safety Liaison Dept, Railway Safety, Evergreen House, 160 Euston Road, London NW1 2DX.




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Part B B1 Purpose

This document defines the mandatory requirements for the provision of lineside signals and the sequences in which signal aspects shall be presented to train drivers, in respect of plain line, diverging junctions and for bi-directional lines, to enable them to:

a) stop safely at a signal at danger

b) regulate train speed to negotiate junctions safely

c) regulate train speed to that of an immediately preceding train.

B2 Application of this document

B2.1 To whom the requirements apply This document contains requirements that are applicable to duty holders of the infrastructure controller category of Railway Safety Case.

B2.2 Compliance requirements B2.2.1 Infrastructure The requirements of this document are mandatory for new Railtrack controlled infrastructure and for alterations to existing Railtrack controlled infrastructure for which approval in principle is given on or after 6 April 2002.

When approval in principle is given before 6 April 2002, but the infrastructure has not yet been brought into service, the design shall be reviewed and, where reasonably practicable, brought into line with the requirements of this document.

B2.2.2 General compliance requirements Until 6 April 2002, or the date by which compliance is achieved (if earlier), the applicable requirements of the predecessor documents shall continue to be met (see Part A for details).

After 6 April 2002, or after the date by which compliance is achieved (if earlier), Railway Group members shall not deviate from the requirements set out in this document.

Where approval in principle is given on or after 6 April 2002, but it is considered not reasonably practicable to comply with the requirements set out in this document, authorisation not to comply shall be sought in accordance with GA/RT6001, GA/RT6004 or GA/RT6006.

B2.3 Exclusions from the application of this document Specifically the contents of this document apply to the design and operational use of signalling systems, on infrastructure controlled by Railtrack that uses lineside signals. It encompasses requirements governing the aspect sequences for signalling on plain line, on the approach to diverging junctions and in respect of bi-directional lines.

This document does not include:

a) specifications for the visual and optical equipment to be used in signals (see GK/RT0031)

b) the requirements for the spacing of signals for compatibility with speeds, gradients and train braking performance (see GK/RT0034)

c) the requirements for the positioning of signals to ensure that they are visible to drivers, and the provision of banner repeaters and co-acting signals (see GK/RT0037)




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d) specific requirements for signalling a train onto an occupied line (see GK/RT0044)

e) the methods of block signalling to be adopted for a section of line. These are specified in the following Railway Group Standards:

GK/RT0041 Track Circuit Block GK/RT0042 Absolute Block GK/RT0051 Single Line Control GK/RT0054 Radio Electronic Token Block

f) requirements for the provision of two aspect (red/green) signalling systems on metro-type railways.

B3 Definitions Area of conflict A section of line ahead of a signal at danger on which a head-on, crossing or same direction converging collision with another legitimately positioned train (whether moving or stationary) could occur in the event of the signal being passed at danger. See also GI/RT7006.

Aspect sequence The order in which the aspects of successive signals are displayed to the driver.

Closing up signal A signal provided to enable a train to closely approach a platform during the time when it is occupied by a departing train. A closing up signal may or may not form part of the standard three or four aspect signalling sequence.

Contra-flow The direction of traffic opposite to the normal direction of flow on bi-directional lines where a predominant direction is specified.

Junction signal A signal protecting any facing points over which more than one main route is available.

In colour light signalled areas, the term junction signal also applies where there are facing points ahead of the signal and the straight-ahead route is not a main signalled route, although it might appear to the driver to be an available route.

Mid-platform signal A signal provided to enable two trains to be positioned at a platform by the use of block signalling techniques. A mid-platform signal may or may not form part of the standard three or four aspect signalling sequence.

Required reading time The sum of: a) the time that is necessary for a driver approaching a signal to achieve the

following:

i) identify the signal that is applicable to the driver

ii) observe the information presented by the signal

iii) interpret the information to determine what action, if any, is required

b) such additional reading time as is reasonably practicable to provide.

Both parts a) and b) of the required reading time are specific to each individual signal.

The concept of required reading time is not applicable where all trains start from rest.




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Signal designation (The terms ‘Passable/Non-passable’ apply for operating purposes, and ‘Automatic/Controlled’ for signal control system purposes.)

Automatic: A signal which does not require specific action by a signaller or automatic route setting equipment in order to show a proceed aspect.

Controlled: A signal that requires a specific action by a signaller or automatic route setting equipment on each occasion that it is required to show a proceed aspect (other than when a controlled signal is arranged to work automatically).

Non-passable: A signal that protects an area of conflict or other infrastructure such that a significant hazard would arise in the event of it being passed at danger without authority. Such signals cannot be passed at danger without specific authority from the signaller, in accordance with the Rule Book

Passable: A signal which is able to be passed at danger without specific authority from the signaller, in accordance with the Rule Book, without a significant hazard arising.

Signal spacing (as applied to this document) The distance between the signal or lineside sign displaying the first cautionary aspect and the signal or lineside sign at which the train is required to stop.

Signal/stop signal The word ‘signal’ includes not only colour light and semaphore signals, but also any lineside sign that performs the function of a signal.

For the purposes of this document, the term stop signals also include shunting signals, stop boards, buffer stops and points set indicators.

Standard three aspect sequence The following colour light aspect sequence is referred to as a standard three aspect sequence:

Green – Single Yellow – Red

Standard four aspect sequence The following colour light aspect sequence is referred to as a standard four aspect sequence:

Green – Double Yellow – Single Yellow – Red

Other defined terms are included in GK/RT0002.

B4 Principles This document supports HMRI Safety Principle 20 – ‘Signalling – Safe routing, spacing and control’.

B5 Provision of stop signals

B5.1 Choice of signal type B5.1.1 Running lines A stop signal that controls a running direction movement along or onto a running line shall be a main signal, except as permitted below.




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It is permissible for a shunting signal to be provided for the control of other than timetabled passenger train movements, subject to consideration of the following factors:

a) the number and proportion of movements that proceed up to the signal ahead on the running line

b) the visibility of the signal ahead upon the movement reaching the running line

c) the distance to the signal ahead on the running line

d) the number and proportion of movements proceeding onto a passenger line that is already occupied.

It is permissible for such a shunting signal to become facing for running movements (ie operated as a preset shunt) and be controlled in accordance with GK/RT0060.

B5.1.2 Sidings A stop signal controlling movements into or along sidings shall be a shunting signal, unless other considerations require it to be a position light aspect on a main signal.

B5.2 Block signalling In all forms of fixed block working, the entrance and exit of every signal section shall be denoted by a stop signal.

The method of block signalling in use shall be reviewed in the event of a proposed change of operational use, to ensure that it is still consistent with the criteria set out in GK/RT0041, GK/RT0042 and GK/RT0051.

B5.3 Facing junctions A stop signal shall be provided on every line on which signalled movements can approach facing points, with the exception of train operated points equipped with points indicators (see section B6.1).

B5.4 Level crossings Where a level crossing is required to be protected by interlocked signals (see GI/RT7012), a stop signal shall be provided on every line on which signalled movements approach the crossing.

B5.5 Conflicting movements A stop signal shall be provided on every line on which signalled movements can approach an area of conflict, including trailing points and other items of infrastructure including movable bridges, so that:

a) trains can be given movement authorities when movements are to be made

b) trains not having a movement authority are stopped before reaching the area of conflict.

B5.6 Lockout systems Where a lockout system for the protection of trackside personnel is provided, a stop signal shall be provided on every line on which signalled movements can approach the area protected by the lockout system, positioned so as to protect the personnel making use of the system.




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B5.7 Signals at point of reversal B5.7.1 Where trains are required to reverse on lines worked by track circuit block or absolute block, a stop signal (referred to in section B5.7.2 as the set-back signal) shall be provided at the point of reversal to authorise the movement in the reverse direction.

B5.7.2 Where practicable, the set-back signal shall be positioned so that:

a) the whole of the train comes to a stand behind the signal after making the outward movement

b) when the outward movement has been completed, the distance between the end of the train and the signal is minimised.

B5.7.3 It is permissible to provide a marker sign, such as a multiple-unit car stop or other appropriate sign, at the outward stopping point to aid the driver. Such a sign shall not be used to define the limit of movement authority for the outward movement.

B5.8 Ground frames Signals on running lines protecting ground frames shall be controlled signals, designated non-passable. It is permissible for movements from running lines into or entirely within sidings accessed by ground frame operated points to be controlled by handsignal.

B6 Constraints on positioning of stop signals

B6.1 Position of signals relative to facing points B6.1.1 Where a signal reads over facing points, it shall be positioned not more than 800 m from the first set of facing points, so that risk due to the following is minimised:

a) the likelihood of the driver forgetting the indicated route

b) the ability to accelerate to greater than the permissible speed over the diverging route.

B6.1.2 The 800 m limit does not apply in respect of any of the following:

a) points which are operated from a ground frame

b) a signal which is positioned parallel with other signals, one of which is within 800 m of facing points, and other factors prevent the positioning of all signals closer to the junction (see GK/RT0037)

c) facing points which are in the same position for all movements from the signal (eg, at the entrance to unidirectional passing loops)

d) facing points which are secured out of use

e) as a temporary consequence of stageworks. In such circumstances an appropriate warning shall be published to drivers using the route during the stageworks.

B6.2 Position of signals relative to points and level crossings




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Where practicable, stop signals shall be positioned so that:

a) the associated overlap is clear of points, level crossings and other moveable infrastructure

b) trains stopped at the signal do not stand over points or level crossings or foul any other line. This necessitates taking into account the stopping positions(s) of trains relative to the signal and the lengths of trains authorised to operate on the route.

Stop signals shall be positioned so that trains stopped at them do not stand over runaway catch points.

B6.3 Position of stop boards Where authority is required to pass a stop board, it shall be positioned such that the authority can be given from the usual working place of the shunter or person-in-charge. Where this is not practicable one of the following options shall be adopted:

a) A means of direct communication (ie telephone or radio) between drivers and the shunter, signaller or person-in-charge shall be provided.

b) The stop board shall be replaced by a signal.

B6.4 Position of signals relative to platforms Stop signals shall be positioned to minimise the risk arising from passenger trains without central door locking or power operated doors stopping with a platform adjacent to only part of the train. See also GK/RT0037.

B6.5 Position of signals relative to hazardous locations B6.5.1 Where practicable, stop signals shall be positioned to avoid the risk of a passenger train stopping in a hazardous location (eg on a viaduct or in a tunnel).

B6.5.2 Where a signal is required at such a location, eg so as to maintain headway, signalling controls shall be applied to the previous signal so as to minimise the risk of a train being brought to a stand at such a location. Where two or more successive signal sections are affected by such controls, the headway is likely to be adversely affected.

B6.5.3 It is not necessary to apply such special controls where the risks associated with trains stopping on viaducts or in tunnels are adequately controlled by other means, such as:

Hazard Control measure

Passengers alighting (other than at a station)

Central door locking or power operated doors on all trains; trackside walkways for train evacuation purposes.

Drivers able to pass signals at danger on own authority

Secure communication between all trains and the controlling signal centre.

SPAD Train protection system fitted to trains and to signals that control movements up to signals at the hazardous location.

Table 1




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B6.5.4 Where practicable, stop signals shall be positioned such that the driver is not exposed to hazards such as live d.c. traction rails when leaving the cab of a train stopped at the signal.

Stop signals shall be positioned so that the exposure of the driver to hazard whilst using the signal post telephone is minimised.

B6.6 Other constraints Subject to all other requirements for the positioning of signals having been met, stop signals shall, where practicable, be positioned such that trains are not required to stop:

a) on severe rising or falling gradients

b) at known sites of poor adhesion.

B6.7 Movements onto occupied running lines GK/RT0044 specifies limits on the distance from the protecting signal to the rear of a train ahead where a movement onto an occupied running line is to be permitted.

B6.8 Overhead electrification systems (25kV a.c. and 1.5kV d.c.) B6.8.1 On lines electrified with overhead systems, stop signals shall be appropriately positioned in relation to a neutral section or section gap to minimise the likelihood of:

a) an electric train with only one pantograph being brought to rest with the pantograph in a neutral section or section gap

b) an electric train restarting from a signal stalling in a neutral section or section gap (allowance being made for the gradient, the attainable speed and the positions of the APC magnets, where provided).

B6.8.2 Stop signals shall be appropriately positioned in relation to relevant overhead line sectioning locations, so as to minimise the likelihood of an electric arc being drawn when a pantograph bridges the sectioning point when the train is travelling slowly or is stationary.

B6.8.3 To ensure that the requirements of sections B6.8.1 and B6.8.2 are met, consideration shall be given to the positions of the pantographs on all types and formations of stock which are authorised to operate on the route.

B6.9 Conductor rail electrification systems B6.9.1 On lines electrified with conductor rail systems, stop signals shall be positioned to minimise the likelihood of trains stalling in conductor rail gaps.

B6.9.2 Where there is a gap between two sections of conductor rail which can be electrically isolated from each other by remote switching, stop signals shall be positioned to ensure that it is not possible for a train stopped at a signal to bridge the gap.




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B7 Designation of main signals

B7.1 Designation of main signals Main signals shall be designated as ‘Passable’ or ‘Non-passable’ for the purpose of specifying whether or not a driver is permitted to pass the signal at danger under his own authority.

The requirements for the provision of identification plates to indicate the designation of signals are set out in section B12 of this document.

B7.2 Non-passable signals in track circuit block areas B7.2.1 A main signal shall be designated as non-passable where a significant hazard would arise from the driver passing a signal at danger under his own authority. A significant hazard shall always be considered to exist in any of the following situations:

a) where the signal protects points within the route up to the signal ahead

b) where the layout is such that a directly opposing route or overlap could conflict with the route or overlap

c) where the signal protects other hazardous features of the permanent way (eg a moveable bridge)

d) where the signal protects a manually controlled level crossing

e) where the signal is required to be held at red on the approach to a traction supply section that is isolated.

B7.2.2 In addition to the circumstances listed in the above section, where operational circumstances exist which make it undesirable for the driver of a train to be allowed to pass a signal at danger under his own authority, the signal shall be designated as non-passable, although it is permissible for the interlocking system to treat it as automatic.

B7.3 Passable signals in track circuit block areas B7.3.1 It is permissible for a main signal to be designated as Passable where none of the significant hazards listed in section B7.2 exists.

B7.3.2 Where the overlap beyond the signal ahead of the signal under consideration contains points or a level crossing but there is no other hazard (as listed in section B7.2), it is permissible, subject to a risk assessment, for the signal under consideration to be designated as passable; although the interlocking system has to treat it as controlled (see GK/RT0060). The risk assessment shall include, but not be limited to, consideration of the following:

a) the distance of the points or level crossing beyond the signal ahead

b) the frequency and nature of conflicting movements

c) the likelihood and consequences of the signal ahead being passed at danger.

B7.4 Intermediate block home signals in absolute block areas A main stop signal shall be designated an intermediate block home signal where it is provided to enable an additional block section to be controlled by one signal box (under the Absolute Block Regulations) and where none of the significant hazards listed in section B7.2 exists.




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B7.5 Stop signals in other than track circuit block areas All main stop signals shall be classified as controlled and non-passable, with the exception of those designated as intermediate block home signals.

B8 Aspect sequences B8.1 Standard three aspect sequence B8.1.1 A driver, running under authority of a green aspect in a three aspect section of line, shall be warned of a stop aspect by the standard three aspect sequence. The minimum signal spacing distances between the yellow and red aspects for various speeds and gradients are set out in GK/RT0034.

B8.1.2 Where the headway requirements are such that that the distance between successive stop signals is greater than the maximum allowed by GK/RT0034, separate distant signals shall be provided.

B8.1.3 Where the permissible speed of trains is greater than 100 mph, four aspect signalling shall be considered (for areas where three aspect signalling would otherwise be adequate), due to the long signal spacing distances which would be encountered by slower speed trains.

In deciding whether to apply four aspect signalling, the following factors shall be considered:

a) range of permissible speeds of trains authorised to use the route

b) range of permissible braking characteristics of trains authorised to use the route

c) infrastructure improvements allowing future increase in permissible speed

d) anticipated incidence of poor visibility (mist, fog, etc)

e) variation in signal spacing distance due to gradient changes

f) variation in required reading time of successive signals (for whatever reason)

g) risks associated with isolated sections of four aspect signalling along a predominantly three aspect route.

B8.2 Modified three aspect sequence Where it is necessary to position signals such that the required spacing between a yellow and a red aspect in the standard three aspect sequence cannot be provided, sufficient warning of the stop aspect shall be provided by means of one of the following:

a) an isolated standard four aspect sequence (preferred method)

b) approach control from red of the previous signal to the signal with sub-standard spacing. The approach control shall be such as to ensure that the speed of the train is reduced to an extent commensurate with the reduced signal spacing to the signal ahead.

The modified aspect sequence is then:

Green – Single Yellow – Red/controlled to Single Yellow – Red

c) the imposition of a speed restriction.




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B8.3 Standard four aspect sequence A driver, running under authority of a green aspect on a four aspect section of line, shall be warned of a stop aspect by the standard four aspect sequence. The minimum signal spacing distances between the double yellow and red aspects for various speeds and gradients are set out in GK/RT0034.

B8.4 Modified four aspect sequences B8.4.1 Where it is necessary to position signals such that the required spacing cannot be provided between a double yellow and a red aspect in the standard four aspect sequence, double yellow aspects shall be additionally displayed at one or more preceding signals such that minimum signal spacing distance is provided between the outermost double yellow aspect and the red aspect. The standard aspect sequence is therefore modified:

Green – Double Yellow - Double Yellow – Single Yellow (*) – Red

Such sequences shall be avoided unless the required headway and signal spacing cannot be achieved by any other means. Additional mitigation shall be provided by a train protection system, fitted as a minimum to the signal marked thus (*) in the diagram above. This system shall be configured to stop movements within the overlap beyond the signal marked when it is displaying a red aspect.

As an alternative to a modified aspect sequence it is permissible, where appropriate, to impose a restriction of the permissible speed (differential if necessary) to enable the required signal spacing distance to be accommodated within a standard aspect sequence.

B8.4.2 Where it is necessary to position signals such that the spacing between the single yellow and the red aspect does not meet the requirements of GK/RT0034 for a four aspect sequence (ie one third of the applicable signal spacing distance), then one of the following modified aspect sequences shall be adopted:

a) The previous signal to the signal at danger shall be approach controlled from red. The approach control shall be such as to ensure that the speed of the train is reduced to an extent commensurate with the reduced signal spacing to the signal ahead. The modified aspect sequence is then:

Green – Double Yellow - Single Yellow – Red/controlled to Single Yellow – Red

b) The previous signal to the signal at danger shall display a single yellow

aspect and the signal previous to that signal shall also display a single yellow aspect. This modified aspect sequence shall be applied only where the previous signal to the signal at danger is a closing up or a mid-platform signal. Additional mitigation shall be provided by a train protection system, fitted as a minimum to the signal marked thus (*) in the diagram below. This system shall be configured to stop movements within the overlap beyond the signal marked when it is displaying a red aspect.

The sequence is then:

Green – Double Yellow - Single Yellow – Single Yellow (*) – Red

Any such sequence shall not include more than two consecutive single yellow aspects.




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B8.4.3 Where, in a modified four aspect sequence, it is necessary that a particular signal never displays a double yellow aspect, that signal shall retain the form of a four aspect head.

B8.4.4 Where, in a modified four aspect sequence, the stop signal is a junction signal for which the diverging route is not approach controlled from red, sufficient distance shall be provided to the signal ahead of the junction on the diverging route to enable a train traversing the junction at the permissible speed for the diverging route to stop at it.

B8.5 Semaphore aspect sequences leading to a stop aspect B8.5.1 Under normal operating circumstances, the minimum warning of a semaphore signal at danger shall be a distant signal caution aspect displayed at least minimum signal spacing distance from the stop signal.

B8.5.2 Where a signal ahead of the first stop signal beyond the distant signal is being held at danger, the preceding stop signal shall also be maintained at danger (preferably by signalling controls but alternatively by instruction) until such time as an approaching train is nearly at a stand.

B8.5.3 A distant signal shall display a clear aspect only when all the stop signals to which it applies are displaying a clear aspect.

B8.5.4 The distant signal shall be capable of displaying caution and clear aspects unless it applies to a place where either:

a) all trains stop, or

b) a very low permissible speed applies (typically 20 mph or less).

In these cases it is permissible for it to be fixed at caution or a distant board provided.

B8.5.5 Where the next signal ahead of a distant signal is a stop signal to which the distant signal does not apply, a repeat distant arm shall be provided in association with that stop signal.

B8.6 Semaphore equivalent aspect sequence Where semaphore signals are replaced by colour light signals and signal spacing in accordance with GK/RT0034 is possible, standard three or four aspect sequences shall be provided.

Where, however, constraints on signal spacing prevent the use of the normal colour light aspect sequences, the aspect sequence principles for semaphore signalling shall be followed, as described in section B8.5. All colour light stop signals (other than the section signal) shall be capable of displaying a yellow aspect, and each stop signal shall display a green aspect only when all stop signals ahead, up to and including the section signal, display green aspects.

B8.7 Aspect sequence where no main route reads up to a signal It is permissible for a signal which cannot be approached under the authority of a main aspect (eg a terminal platform starting or yard exit signal) to show a red aspect with no preceding warning signal.




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The following sequence shall be displayed when such a starting signal is displaying a proceed aspect with the next signal ahead at danger:

Single Yellow – Red

When the starting signal is off while the second signal beyond the starting signal is at danger, the following sequence shall be displayed, except in the circumstances described below:

Green – Single Yellow – Red

This sequence shall not be displayed where the yellow aspect of the signal immediately beyond the starting signal would alone provide insufficient signal spacing distance to the red aspect in accordance with GK/RT0034, having regard to attainable speed. In such circumstances the starting signal shall display a double yellow aspect.

B8.8 Aspect sequence up to a points indicator A points indicator shall be preceded by a signal (at the appropriate signal spacing distance) displaying a caution aspect, except where all trains start from rest within sight of the indicator. It is permissible for the caution aspect to take the form of a colour light yellow aspect, a semaphore distant signal arm fixed in the caution position, or a distant board.

B8.9 Aspect sequence up to a stop board A stop board shall be preceded by a signal displaying a caution aspect, except where it cannot be approached by a running movement. It is permissible for such a signal to take the form of a colour light yellow aspect, a semaphore distant arm fixed in the caution position or a distant board, positioned at the appropriate signal spacing distance.

B8.10 Aspect sequence up to a buffer stop A buffer stop shall be regarded as a stop aspect for the purposes of aspect sequences and the cautionary aspect, or aspect sequence, appropriate to the prevailing type of signalling (ie colour light or semaphore) shall be displayed at signal spacing distance on the approach. It is permissible for a distant board to be provided.

B8.11 Stepping down of aspect In track circuit block areas, where technically feasible, failure of illumination of a proceed aspect of a colour light signal shall cause the display of a more restrictive aspect in that signal, with the aspects in the previous signal(s) adjusted to preserve a correct sequence.

Failure of illumination of the most restrictive aspect shall cause the previous stop signal to display a red aspect.

B8.12 Prohibited aspect sequences Successive signals shall not simultaneously display the following:

a) a red aspect immediately preceded by any colour light aspect other than a single yellow aspect

b) a single yellow aspect followed by any aspect other than red, except as permitted in sections B8.4.2b and B8.6

c) a red aspect immediately preceded by a semaphore distant arm in the ‘off’ position

d) a semaphore stop signal arm in the ‘on’ position preceded by a semaphore distant signal arm in the ‘off’ position




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e) a semaphore stop signal arm in the ‘on’ position preceded by any colour light aspect other than a single yellow aspect.

B9 Aspect sequence transitions

B9.1 Segregation of three and four aspect sequences B9.1.1 The number of transitions between three and four aspect signalling shall be kept to a minimum. However, where signal spacing and headway considerations require such boundaries, each group of three or four aspect signals shall consist of a sufficient number of signals (typically three complete sequences) to establish a clear pattern for the driver (except as permitted by section B9.1.2).

B9.1.2 It is permissible for an isolated four aspect sequence to be displayed in an otherwise three aspect sequence (see section B8.2), but an isolated three aspect sequence shall not be displayed in a four aspect section of line, except in respect of a signal which has no main signal route reading up to it, as detailed in section B8.7 of this document.

B9.1.3 It is permissible for parallel running lines signalled for movements in the same direction to be considered as independent sections of line for the purpose of this section B9.

B9.2 Transition from three aspect to four aspect At the transition from continuous three to four aspect signalling, one of the following arrangements shall be applied (see diagrams in Appendix 1):

a) The first four aspect signal displays a single yellow up to the next signal at red or a double yellow up to the next but one signal at red. A train protection system shall be provided at (as a minimum) the last signal in the three aspect sequence (signal 7 in Appendix 1 Figure A1.1).

b) The first four aspect signal shows only red/double yellow/green and an additional distant signal (yellow/double yellow/green) is provided between it and the next stop signal ahead.

b) The first four aspect signal is approach controlled from red to yellow when the next signal ahead is at red.

In deciding which method to apply, the following factors shall be considered:




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Method Factors

a) First caution for two consecutive signals

a) The relative likelihood of a driver seeing the first 4-aspect signal (signal 5 in Appendix 1, Figure A1.1) at single yellow and double yellow respectively.

b) The likelihood of a driver mis-reading a single yellow aspect at signal 5 as double yellow (because he usually receives a double yellow).

The distance from the double yellow to the red (signal 9 in Appendix 1, Figure A1.1) will generally be greater than the signal spacing distance by at least 50%, so that a risk assessment in accordance with GK/RT0034 will be necessary.

b) Additional distant signal

The practicability of fitting in an isolated distant signal in respect of:

a) distance to facing points, level crossings

b) the effect on signals on parallel lines

c) adequacy of overlaps and standage

d) position of critical electric traction sectioning points

c) Approach control a) the effect of approach control from red on driver anticipation.

b) secondary hazards created by loss of headway and consequent increase in incidence of red signals seen by drivers.

Table 2

A further factor for consideration is need for consistency, ie the undesirability of mixing methods a) and b) in successive transitions.

B9.3 Transition from four aspect to three aspect At the transition from four to three aspect signalling, the first signal in the three aspect sequence (ie which shows a single yellow aspect when the preceding signal is at green) shall not have the appearance of a four aspect head. This prohibition is not applicable where the transition occurs at a junction signal in respect of a branch or slow line.

If the first signal beyond the junction on the branch or slow line is at least minimum signal spacing distance from the next signal beyond, the junction signal shall display a green aspect when this next signal is at single yellow.

B9.4 Transition from colour light to semaphore At the transition from colour light to semaphore signalling, it is permissible for the last colour light signal to be one of the following:

a) a colour light distant signal

b) a three aspect stop signal at the correct signal spacing distance (ie also performing the function of the distant for the semaphore stop signal ahead)

c) a stop signal capable of showing single yellow at less than signal spacing distance (but at least one-third of signal spacing distance – see GK/RT0034)




RAILWAY SAFETY 1 9


from the semaphore stop signal ahead, preceded by a signal capable of showing double yellow, which is located at not less than minimum signal spacing distance from the semaphore stop signal

d) a red/green stop signal.

B9.5 Transition from semaphore to colour light At the transition from semaphore to colour light signalling, it is permissible for the distant signal preceding the first colour light stop signal to be either of the following:

a) colour light

b) power worked semaphore.

It is not permissible for the last semaphore stop signal to have a colour light lower distant on the same post.

B9.6 Interfaces with other signalling systems Within the transition zone between different types of lineside signalling systems, all route indications and signal aspects shall be displayed so as to permit the driver to comply with subsequent signals, including route indications, and subsequent changes in permissible speed over the route set. A specific example of such arrangements is given in Appendix 2.

The core requirements for transitions between lineside and cab signalling systems are set out in GE/RT8026.

B10 Junction signalling B10.1 Method of junction control In order to enable a driver to control the train speed correctly through a diverging junction, an appropriate combination of aspect sequences and approach control shall be applied. The permitted combinations for colour light signalling and the criteria for their use are set out in Appendix 3.

The requirements for the signing of permissible speeds over a junction are set out in GK/RT0038.

B10.2 Indication of route B10.2.1 The route set at a colour light junction signal shall be indicated to the driver by means of one of the following:

a) a position light junction indicator

b) an alphanumeric route Indicator

c) a combination of a position light junction indicator (to define routing) and an alphanumeric route indicator (to define destination); see section B10.3c).

Subject to approach speed and sighting requirements, position light junction indicators shall be provided for simple junctions, and standard alphanumeric route indicators for complex junctions (eg at the approaches to major stations).

GK/RT0031 sets out constraints on:

a) the use of standard alphanumeric route indicators

b) the particular route indications permitted to be displayed, for both position light junction indicators and for alphanumeric route indicators.




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B10.2.2 Where it is self-evident that the main or highest speed route lies straight ahead, then no indication shall be given for that route unless this is required to facilitate consistency of route indications as required by GK/RT0037.

Where there is no route ahead of a junction signal which is self evidently the main or highest speed route, a route indication shall be provided for all signalled routes.

Where the track layout is such that the straightest route through the junction is an unsignalled route, but which might appear to a train driver to be a legitimate route, a route indication shall be provided for all signalled routes.

Where routes from a signal with position light junction indicators diverge but then cross on the level before reaching the signal ahead, the junction indicator positions shall reflect the order in which the divergences from the straight route occur, rather than the geographical positions of the signals ahead.

B10.3 Alternative routes to a common destination One of the following arrangements shall be applied to a signal that has more than one route to a common destination:

a) The same route indication shall be displayed for all routes. Any route having a permissible speed of more than 10 mph lower than the highest speed applicable to that destination shall be approach controlled to an extent commensurate with the lower permissible speed. The same route indication shall not be given for alternative routes with a speed differential of more than 10 mph.

b) The routing and destination shall be displayed by different indications of the route indicator or position light junction indicator (see section B10.2.1).

c) Exceptionally, where the complexity of the layout warrants, the routing and destination shall be displayed by a combination of route indicators, the routing by a position light junction indicator and the destination by an alphanumeric route indicator.

B10.4 Unrestricted aspect sequence Where an unrestricted aspect sequence is applied to a diverging route, both the junction signal and the preceding signals shall be free to display aspects as determined by the aspects beyond the junction for the route set.

B10.5 Approach control from yellow (free yellow) B10.5.1 Where approach control from yellow is applied to the junction signal, it shall clear from yellow to a less restrictive aspect (as determined by the aspect displayed at the signal ahead) when the approaching train has passed the double yellow and reached a position from which the route indication and main signal are both readable (see GK/RT0031 Issue 4, Table 16). Wherever possible, this shall be before reaching the associated AWS inductor.

B10.5.2 Where there is a significant risk of reading through from the junction signal to the exit signal of the route from the approach controlled signal, the latter shall be held at red until such time as the junction signal is required to clear from yellow.

B10.6 Flashing yellow aspects B10.6.1 In three aspect signalling a flashing single yellow aspect shall be displayed in the following sequence:

Green – Flashing Single Yellow – Single Yellow (Junction Signal)




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In four aspect signalling flashing yellow aspects shall be displayed in the following sequence:

Green – Flashing Double Yellow – Flashing Single Yellow – Single Yellow (Junction Signal)

The sequences defined above shall not be extended by displaying flashing aspects at a greater number of signals than shown. No signal shall be capable of displaying flashing aspects relating to more than one junction signal.

B10.6.2 The positioning of junction signals shall, if possible, be such that the driver of an approaching train can read the route indicator at the same time as the main aspects. However, if this is not possible, then:

a) the junction signal shall be maintained at red if the approaching train has reached a position corresponding to less than the required reading time on the approach to the signal which would display flashing single yellow, and

b) the junction signal shall be placed and maintained at red if the signal that should display flashing single yellow fails to commence flashing or subsequently fails.

In both of the above cases, the junction signal shall subsequently be approach controlled from red.

B10.6.3 The junction signal shall clear from yellow to a higher aspect (as determined by the aspect displayed at the signal ahead) when the approaching train has passed the flashing single yellow and reached a position from which the route indication and main signal are both readable. Wherever possible, this shall be before reaching the associated AWS inductor (see GK/RT0031 Issue 4, Table 16).

B10.6.4 Where there is a significant risk of reading through from the junction signal to the exit signal of the route from the approach controlled signal, the latter shall be held at red until such time as the junction signal is required to clear from yellow.

B10.6.5 A flashing yellow aspect sequence shall be inhibited when the signal ahead of the junction on the diverging route is at red, unless one of the following conditions applies:

a) The controls for the signal ahead are satisfied (except approach control) and the signal is therefore capable of clearing to a proceed aspect once any approach control conditions have been satisfied.

b) The signal ahead is at the end of a loop or station platform line where the drivers of all trains expect to stop.

B10.7 Colour light splitting distant aspects B10.7.1 Where advance warning of a diverging route is conveyed by an aspect sequence employing splitting distant aspects, the junction signal shall be free to display aspects as determined by the aspect of the signal ahead. The signal immediately preceding




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the junction signal shall display the splitting distant aspect appropriate to the aspect displayed by the junction signal.

See Appendix 4 for the aspects displayed in the main and offset heads and for aspect sequences approaching junctions controlled by splitting distant signals. See GE/RT8035 for the AWS indications to be given at colour light splitting distant signals.

B10.7.2 An outer splitting distant signal shall be provided only where a splitting distant alone cannot be positioned so as to give sufficient advance warning of a divergence for either of the following purposes:

a) to enable the necessary reduction of speed to meet the permissible speed over or beyond a turnout

b) to enable a driver whose train which is being misrouted to stop before reaching the junction signal, where the misrouting of trains would give rise to a safety hazard (eg gauge or traction system incompatibility or serious operational inconvenience).

Where an outer splitting distant is provided, the signal preceding the junction signal becomes an inner splitting distant signal. However, the use of an outer splitting distant shall be avoided wherever possible, eg by positioning the splitting distant at an appropriate distance from the junction signal (within the constraints set out in GK/RT0034).

B10.7.3 The positioning of junction signals shall, if possible, be such that the driver of an approaching train can read the route indicator at the same time as the main aspects. However, if this is not possible, then:

a) the junction signal shall be maintained at red if the approaching train has reached a position less than the required reading time on the approach to the signal which would display the inner splitting distant indication, and

b) the junction signal shall be placed and maintained at red if the signal that should display the inner splitting distant indication fails to do so or subsequently fails.

In both of the above cases, the junction signal shall subsequently be approach controlled from red.

B10.7.4 Splitting distant aspect sequences are not permitted to extend back to another junction signal if the sequence would apply to any route other than the main (highest speed) route at that junction signal.

B10.8 Approach control from red B10.8.1 Where approach control from red is applied to the junction signal, the approach aspect sequence shall be identical to the sequence displayed when the signal is at danger for any other reason.

B10.8.2 The junction signal shall clear from red to a higher aspect (as determined by the aspect displayed at the signal ahead) when the approaching train has passed the single yellow and reached a position from which the route indication and main signal are both readable – see GK/RT0031, Issue 4, Table 16. Wherever possible, this shall be before reaching the associated AWS.

B10.8.3 Where a banner signal applies to the junction signal, either




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a) splitting banners shall be provided, or

b) the clearance of the junction signal for the approach controlled route shall be delayed until the train has passed the banner.

B10.9 Provision for facilities for temporary approach control Facilities shall be provided to enable temporary approach control from red to be enforced in the event that it is necessary to impose a temporary or emergency speed restriction through or beyond junctions on a route signalled by any of the following:

a) an unrestricted aspect sequence (see section B10.4)

b) a free yellow aspect sequence (see section B10.5)

c) a flashing yellow aspect sequence which is applicable to more than one route (see Appendix 1).

B10.10 Semaphore aspect sequences for junctions B10.10.1 The route set at a semaphore junction signal shall be indicated to the driver by means of multiple semaphore arms, displayed in accordance with the principles defined in GK/RT0031 and GK/RT0037, and/or by an alphanumeric route indicator in association with a single semaphore arm.

B10.10.2 A semaphore distant signal shall not be capable of being cleared for a diverging route, except where it forms part of a splitting distant signal.

B10.10.3 It is permissible to provide semaphore splitting distant signals where the use of a single distant arm would be too restrictive to enable trains to take the diverging route at the permissible speed (taking into account also the permissible speed beyond the junction on the diverging route).

B10.10.4 Where a semaphore splitting distant signal is provided, the appropriate distant signal arm shall be off only when the corresponding junction signal arm, and any other stop signals to which the distant arm applies, are also off. Where a semaphore stop signal on the approach to a junction signal conveys an indication of the route to be taken at the junction, the driver shall be given equivalent route information at any preceding stop signals controlled from the same signal box.

See GE/RT8035 for the AWS indication to be given at a semaphore splitting distant signal.

B10.10.5 Where the next signal ahead of a splitting distant signal is a stop signal to which the splitting distant signal does not apply, repeat splitting distant arms shall be provided in association with that stop signal (see section B8.5.5).

B10.11 Route indicators for position light signals The requirements for the application of route indicators to position light signals are set out in GK/RT0031 (Lineside Signals and Indicators).

B10.12 Prohibited aspect sequences at junctions The following combinations are prohibited:

a) a flashing single yellow aspect immediately preceded by a signal displaying a flashing single yellow aspect




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b) a flashing double yellow aspect immediately preceded by a signal displaying a flashing single yellow aspect or flashing double yellow aspect

c) a flashing double yellow aspect immediately followed by a signal displaying any aspect other than flashing single yellow

d) any sequence involving both a flashing colour light aspect and a semaphore signal

e) a free yellow aspect sequence and a flashing yellow sequence for different routes from the same junction signal

f) flashing aspects relating to more than one junction signal

g) a flashing aspect and a splitting distant aspect sequence for different routes from the same junction signal.

B11 Bi-directional signalling

This section does not apply to adjacent lines signalled as independent single lines by one of the means set out in GK/RT0051.

All other requirements of this document apply to signals for both directions on bi-directional lines.

Two forms of bi-directional signalling are permitted, as set out below:

B11.1 Full bi-directional signalling B11.1.1 For every signal provided, there shall be a parallel signal for movements in the same direction on the adjacent line(s). GK/RT0037 specifies other requirements for the positioning of parallel signals.

B11.1.2 On bi-directional lines where a predominant (normal) direction of traffic is designated, it is permissible for signalling in the contra-flow direction to be three aspect whilst that in the same (normal) direction on the adjacent line is four aspect, provided that a lower permissible speed is applied for contra-flow direction movements, to correspond with the reduced signal spacing distance between the caution aspect and the stop signal.

B11.2 Reduced capacity bi-directional signalling B11.2.1 Where the headway requirement for the contra-flow direction does not warrant the same signal spacing as is provided for the normal direction, it is permissible to provide fewer signals, but consecutive stop signals shall not be more than ten miles apart.

Where provided, contra-flow direction signals shall be positioned parallel to normal direction signals on the adjacent line(s), subject to signal sighting requirements.

B11.2.2 It is permitted for the provisions of section B11.1.2 to be applied.

B12 Identity of signals B12.1 Signal numbering B12.1.1 Each signal shall have an identity that is unique to its controlling signal box or locality, comprising the signal box prefixes code, the signal number and, where required, a suffix (see section B12.1.3).




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The number of each signal worked by a lever shall be the same as the lever number.

All signals, including automatic and distant signals, except distant signals worked from the same lever as a stop signal, (see section B12.1.3) shall be individually numbered as part of a sequence. Separate sequences shall be used for:

a) running signals (including slots) and equivalent stop or distant boards

b) shunting signals (including slots), limit of shunt signals and equivalent stop boards.

B12.1.2 Except where signals are worked by levers, the rules for determining the sequences of numbers are as follows:

a) The sequences of numbers shall be separate and distinct from other numbered functions such as points, ground frame releases and lockout systems.

b) The sequences shall be logical and the rationale for the numbering shall be documented as part of the signalling design records.

c) Odd numbers shall be used for down direction signals and even numbers for up direction signals.

d) Odd numbers shall usually ascend and even numbers descend in the direction of traffic flow.

e) It is permissible to vary the numbering sequence to achieve a logical arrangement, eg to give platform-starting signals at a terminal station the same numbers as their platforms.

f) If there is more than one running line in each direction (eg fast and slow) the numbers for each line shall be in separate sequences.

g) As far as possible, train drivers shall be presented at successive signals with signal numbers which are consecutive odd or even numbers.

h) Where up to five signals applying to traffic in the same direction are positioned side by side the last digit of each signal identity shall be different.

i) Where more than five signals are positioned side by side, the last digit of the identities of adjacent signals shall be different.

Exceptions to the above are permitted to achieve consistency with existing numbering sequences.

B12.1.3 The following signal suffixes shall be used for the applications indicated and not for any other purpose:

BR – for a banner repeating signal, the number being the same as that of the repeated signal.

CA – for a co-acting signal, the number being the same as that of the primary signal.

R – solely for a distant signal worked from the same operating device as a stop signal, the number being that of the stop signal.

RR – solely for an outer distant signal worked from the same operating device as a stop signal, the number being that of the stop signal.




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B12.2 Signal identification plates B12.2.1 Identification plates as depicted in GK/RT0033 shall be provided at the following signals:

a) Colour light signals.

b) Semaphore running signals.

c) Position light shunt and limit of shunt signals.

d) Banner repeater signals.

e) Stop boards.

f) Distant boards.

Identification plates are not required at other types of signal or board.

B12.2.2 In addition, the following signals require the appropriate sign, which shall be combined with the identification plate (see GK/RT0033):

a) Passable signals (auto plate).

b) Intermediate block home signals.

c) Colour light distant signals.

B12.2.3 Identification plates at main signals shall display the signal box prefix code, the signal number and a suffix where required. For shunt signals, it is permissible to omit the signal box code.

B12.2.4 Identification plates shall indicate, by means of an arrow, the line to which the signal applies where the signal is positioned on the right hand side of the line in the direction of traffic flow. It is permissible to provide an arrow for signals on the left hand side, where this helps to avoid confusion.




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Appendix 1 (This Appendix is mandatory)

Transition from Three to Four Aspect Signalling

3asp 3asp 4asp 4asp 4asp 4asp 4asp

1 3 5 7* 9 11 13

* Train protection system (eg TPWS) required at this signal (No. 7)

G

G

G

G

G

G

G

Y

Y

Y

Y

Y

Y

R

R

R

R

R

YY

YY

YY

YY

YY

Figure A1.1 Signal 3 providing first caution for both signal 7 and signal 9 (Section B9.2 a)

3asp 3asp 4asp 3asp YGY 4asp 4asp 4asp

1 3 5 7 9 11 13

G

G

G

G

G

G

Y

Y

Y

Y

Y

R

R

R

R

YY

YY

YY

YY

YY

G

Figure A1.2 Additional distant signal 7 provided (Section B9.2 b)




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Transition from Three to Four Aspect Signalling

3asp 3asp 3asp 4asp 4asp 4asp 4asp

1 3 5 7 9 11 13

G

G

G

G

G

Y

Y

Y

Y

Y

R

R

R

R

YY

YY

YY

YY

G

Y R

#1

#1: approach control condition Figure A1.3 Signal 7 approach controlled from red when signal 9 at red (Section B9.2 c)




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Appendix 2 (This Appendix is for information)

Interface with London Underground lineside signalling

This Appendix details the historical interface arrangements between Railtrack and LUL infrastructure. LUL use a two aspect (red/green) signalling system. A green aspect permits trains to travel at permissible speed until sighting a red aspect. Where sighting distances are less than train stopping distances, repeater signals (yellow/green) are provided. An exception applies on lines traversed by non-LUL trains, where aspect sequences complying with this document are provided.

The following examples apply to interfaces that are traversed only by LUL trains. Where non-LUL trains cross the interface, aspect sequences and signal spacing distances that comply with Railway Group standards are provided.

When travelling on Railtrack controlled infrastructure, the aspect sequences mandated in this document also apply to LUL trains.

i) Railtrack to LUL The last Railtrack signal is a stop signal.

Where the first LUL stop signal is at greater than train stopping distance from the last stop signal on Railtrack controlled infrastructure, the latter is a two aspect (red/green) stop signal.

An exception occurs where the first LUL stop signal would otherwise have required a yellow/green repeating signal visible to the driver of a train standing at the last Railtrack controlled stop signal. In such circumstances, the yellow/green repeating signal is omitted, but the last Railtrack controlled signal is capable of displaying a yellow aspect to provide an aspect sequence complying with this document.

Where the first LUL stop signal is at less than train stopping distance from the last Railtrack controlled stop signal, an aspect sequence complying with this document is provided up to the first LUL stop signal.

ii) LUL to Railtrack The aspect sequence to the first stop signal on Railtrack controlled infrastructure maintains the minimum signal spacing distance from the first caution to the stop signal. Where necessary, a repeating signal associated with the last LUL stop signal is provided to achieve such an aspect sequence.




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Criteria for the selection of method of junction control (colour light signalling) In order to enable the driver to control the train speed correctly through a diverging junction, an appropriate combination of aspect sequences and approach control has to be applied. The permitted forms of aspect sequences and approach control are set out below, together with the criteria for their provision. In the table, the term ‘straight-ahead route’ refers to the higher speed route (for which a normal aspect sequence applies and no route indication or approach control is provided), and the term ‘diverging route’ refers to the lower speed route (to which the permitted forms of aspect sequence and approach control apply).

In selecting an appropriate form of junction control, consideration shall be given to the methods in the order listed, cognisance being taken of the aspect sequences prohibited in sections B8.12 and B10.12.

Method of control

Criteria for use (all criteria shall be met)

Section reference

Unrestricted aspect sequence

a) Not more than 10 mph difference between the permissible speeds of the straight-ahead and diverging routes through and immediately beyond the junction.

b) No safety hazard would arise if the train is wrongly routed at the junction (eg gauge or traction supply incompatibility; serious operational inconvenience with consequential secondary safety hazards).

Notes: i) It is permissible to apply unrestricted aspect sequences to more than one diverging route at a junction signal.

ii) It is permissible for the aspect of a junction signal to be unrestricted in respect of trains approaching from a direction over which the permitted speed is not greater than 10 mph more than the turnout speed, even though approach control is required for the straight route approaching the signal.

B10.4

Free yellow at junction signal

a) More than 10 mph difference between the permissible speeds of the straight-ahead and diverging routes through and immediately beyond the junction.

b) The signal preceding the junction signal is able to show double yellow as part of a four aspect sequence applicable to the diverging route.

c) No safety hazard would arise if the train were wrongly routed at the junction (eg gauge or traction supply incompatibility; serious operational inconvenience with consequential secondary safety hazards).

d) Approach control from red is too restrictive to enable trains to take the diverging route at the permissible speed (taking into account also the permissible speed beyond the junction on the diverging route).

e) There is sufficient distance from the junction signal to the junction itself for the driver to reduce speed to the permissible speed through and immediately beyond the junction on the diverging route (taking into account the fact that a double yellow aspect is displayed at the signal preceding the junction signal but without any advance indication of which route is set at the junction).

f) There is sufficient distance from the junction signal to the next stop signal on both the straight-ahead and diverging route that a driver (having received a double yellow at the signal preceding the junction signal but without any advance indication of which route is set at the junction) can bring the train to a stand at whichever stop signal beyond the junction he is routed to, even if he was

B10.5




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Method of control

Criteria for use (all criteria shall be met)

Section reference

expecting to be routed the other way.

Notes: i) It is permitted to apply free yellows to more than one diverging route at a junction signal if there is no more than 10 mph difference in permissible speed between the highest speed diverging route and the other diverging route(s) under consideration.

ii) Sections e) and f) above are required to be met by all classes of train authorised to run on the route.

Flashing yellows

a) It is not possible to apply either an unrestricted aspect sequence or a free yellow at the junction.

b) Approach control from red is too restrictive to enable trains to take the diverging route at the permissible speed (taking into account also the permissible speed beyond the junction on the diverging route).

Note: It is permitted to apply flashing yellows to more than one diverging route at a

junction signal if there is no more than 10 mph difference in permissible speed between the highest speed diverging route and the other diverging route(s) under consideration, and any safety hazards or serious operational inconvenience arising from misrouting are common to all routes to which the flashing yellow aspects apply.

B10.6

Splitting distants

a) It is not possible to apply either an unrestricted aspect sequence or a free yellow at the junction (see note 1).

b) The use of a flashing yellow sequence or approach control from red is too restrictive to enable trains to take the diverging route at the permissible speed (taking into account also the permissible speed beyond the junction on the diverging route).

Notes: i) It is permitted to use a splitting distant aspect sequence where a safety

hazard or serious operational inconvenience precludes the use of an unrestricted or free yellow aspect sequence.

ii) Only one offset head shall be provided on a splitting distant signal.

B10.7

Approach control from red

Approach control from red shall be applied to:

a) all diverging routes where the criteria for less restrictive aspect sequences (as listed above) cannot be met

b) other diverging routes at a junction that is equipped with splitting distants for one of its diverging routes

c) other diverging routes at a junction that is equipped with flashing aspects, but to which the flashing aspect sequences do not apply

d) other diverging routes at a junction that is equipped with a free yellow, but to which the free yellow aspect sequence does not apply.

Note: There are also circumstances when a junction is equipped with flashing

yellows or splitting distants but it is not appropriate to use them, approach control from red being applied instead. See sections B10.6.2, B10.6.5 and B10.7.3.

B10.8




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Figure A3.1




RAILWAY SAFETY 3 3



Colour light splitting distant signals: Permissible arrangement of aspects

Inner Outer Profile Profile

Offset Main Meaning Offset Main Meaning

Stop

Stop

Caution

Caution

Preliminary caution (lower speed divergence to left at junction signal)

Preliminary caution

Preliminary caution (straight-ahead route set at junction signal)

Clear (lower speed divergence to left at junction signal)

Clear (lower speed divergence to left at junction signal)

Clear (straight-ahead route set at junction signal)


Figure A4.1 Splitting distant aspects for diverging route to left




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Colour light splitting distant signals: Permissible arrangement of aspects Inner Outer

Profile Profile Offset Main Meaning Offset Main Meaning

Stop

Stop

Caution

Caution

Preliminary caution (lower speed divergence to right at junction signal)

Preliminary caution

Preliminary caution (straight-ahead route set at junction signal)

Clear (lower speed divergence to right at junction signal)

Clear (lower speed divergence to right at junction signal)



Figure A4.2 Splitting distant aspects for diverging route to right




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Colour light splitting distant signals: Permissible aspect sequences

Left hand divergence; diverging route set

Left hand divergence; straight ahead route set

Right hand divergence; straight ahead route set

Right hand divergence; diverging route set

Figure A4.3 Colour light splitting distant signals: Permissible aspect sequences

Appendix 4 Legend

Green

YellowR

ed

Lit Aspects:

Unlit Aspect

Lit Position Light Junction Indicator

Unlit Position Light Junction Indicator




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References

GA/RT6001 Railway Group Standards Change Procedures

GA/RT6004 Temporary Non-Compliance with Railway Group Standards

GA/RT6006 Derogations from Railway Group Standards

GE/RT8026 Safety Requirements for Cab Signalling Systems

GI/RT7012 Design, Construction and Maintenance of Level Crossings

(Due for publication in 2002)

GE/RT8035 Automatic Warning System (AWS)

GI/RT7006 Risk Assessment to Prevent & Mitigate Over-runs

GK/RT0002 Glossary of Signalling Terms

GK/RT0031 Lineside Signals and Indicators

GK/RT0033 Lineside Signs

GK/RT0034 Lineside Signal Spacing

GK/RT0037 Signal Positioning and Visibility

GK/RT0038 Signing of Permissible Speeds and Speed Restrictions

GK/RT0041 Track Circuit Block

GK/RT0042 Absolute Block

GK/RT0044 Controls for Signalling a Train onto an occupied Line

GK/RT0060 Interlocking Principles

GK/RT0051 Single Line Control

GK/RT0054 Radio Electronic Token Block

GK/RT0207 Signalling Design Production

GO/RT3000 Rule Book

The Catalogue of Railway Group Standards and the Railway Group Standards CD-ROM give the current issue number and status of documents published by Railway Safety.



Provision of Lineside Signals - RSSB Iss 2.pdf · 3 Criteria for the selection of method of...

Documents

Transcript of Provision of Lineside Signals - RSSB Iss 2.pdf · 3 Criteria for the selection of method of...