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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 2001 Railway Safety

Railway Group Standard GK/RT0037 Issue Four Date October 2001

Signal Positioning and Visibility

Synopsis This document defines the requirements for positioning signals and indicators to ensure adequate viewing and clarity of meaning for drivers.

Submitted by Paul Woolford Standards Project Manager

Authorised by Brian Alston Controller, Railway Group Standards

Withdrawn Document Uncontrolled When Printed

jtrousdale

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Railway Group Standard GK/RT0037 Issue Four Date October 2001 Page 1 of 38

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 2 A5 Health and safety responsibilities 3 A6 Technical content 3 A7 Supply 3

Part B

B1 Purpose 4 B2 Application of this document 4 B3 Definitions 5 B4 General requirements for positioning and visibility of signals 7 B5 Colourlight main signals and associated route indicators 10 B6 Position light signals and associated route indicators 14 B7 Semaphore signals and signs that perform the function of signals 15 B8 Use of banner repeating and co-acting signals 18 B9 Platform equipment 19 B10 Miscellaneous technical requirements 20 B11 Signal sighting process 23 B12 Records 26

Appendices 1 Examples of a typical signal sighting form 28 2 Guidance on minimum reading time 32 3 Guidance for assessing interruptions to view 34

References 36



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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 One October 1994 Original Document

Replaced JDP C005 Two February 1996 Revised

Replaces issue One Three December 1997 Revised

Replaces issue Two Four October 2001 Revised

Replaces issue Three

Issue 4 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 06 October 2001.

This document comes into force on 01 December 2001.

The date by which compliance with the requirements of this document is to be achieved is set out in Part B2.

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

Railway Group

Standard

Iss. No.

Title RGS sections to be superseded

Date(s) as of which sections are superseded

GK/RT0037 3 Signal Sighting

5 7 All remaining sections

When the compliance date of GE/RT8048 Issue One is reached When the compliance date of GE/RT8034 Issue One is reached 01 Dec 2001

GK/RT0037 issue 3 is withdrawn when the compliance dates for both GE/RT8034 and GE/RT8048 have been reached.

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.

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



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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:

Francis How, Principal Signalling and Telecommunications Engineer, Railway Safety

Richard Evans, Principal, Operations, Railway Safety

Enquiries to be directed to the Industry Safety Liaison Dept – 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

The purpose of this standard is to define the requirements for positioning signals and indicators to ensure adequate viewing and clarity of meaning for drivers.

B2 Application of this document

B2.1 To whom the requirements apply This document contains requirements that are applicable to Railway Safety and duty holders of the following categories of Railway Safety Case:

a) infrastructure controller

b) station operator

c) train operator

Under the Railways (Safety Case) Regulations 2000, the duty holder at a station (as defined in those Regulations) is responsible for ensuring that the requirements of Railway Group Standards are complied with. At a station, contractual arrangements (including a lease) do not of themselves relieve the duty holder of his obligations under those Regulations.

B2.2 Compliance requirements The requirements of this document are mandatory for all fixed signals, signs that perform the function of signals, and associated indicators, where these form part of Railtrack controlled infrastructure, and apply when such signals are either new, modified in form or re-positioned.

The requirements of this document are mandatory for work where Approval in Principle is given on or after 01 December 2001. When Approval in Principle is given before 01 December 2001, but the infrastructure has not yet been brought into service, the design shall be reviewed and, where reasonably practicable, brought into compliance with the requirements of this document. Where it is not reasonably practicable to do so, the situation shall be regularised by means of a non-compliance or derogation (see section B2.2.4).

In respect of remedial action associated with signals that are the subject of a SPAD investigation, consideration shall be given to implementation of those technical requirements set out in this document which are both reasonably practicable in the circumstances, and have the potential to reduce the risk of a signal being passed at danger in the future.

B2.2.1 Infrastructure controller Duty holders of this category of railway safety case shall comply with all parts of this document.

B2.2.2 Station operator Duty holders of this category of railway safety case are required to provide competent persons to participate in signal sighting committees as specified in section B11.4. As a consequence, they need to be aware of the contents of this entire document.

B2.2.3 Train operator Duty holders of this category of railway safety case are required to provide competent persons to participate in signal sighting committees as specified in section B11.4. As a consequence, they need to be aware of the contents of this entire document.



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B2.2.4 General compliance requirements Until the compliance date, or the date by which compliance is achieved (if earlier), the applicable requirements of GK/RT0037 issue three shall continue to be met (see Part A for details).

After the compliance date, 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 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 Buffer stop lights do not have to comply with this document.

B2.4 Related requirements in other documents Other requirements relating to the provision and positioning of signals and signs are contained in GK/RT0031, GK/RT0032, GK/RT0033, GK/RT0034, and GK/RT0044.

Requirements for the maintenance of signal visibility and for the reassessment of the visibility of existing signals in connection with alterations to other assets or following allegations of poor visibility are contained in GE/RT8034.

Requirements for the reassessment of the visibility of existing signals following an overrun (Signal Passed At Danger - SPAD) are contained in GO/RT3252.

Requirements for the positioning of signal post telephones are contained in GE/RT8048.

B2.5 Supporting documents There are no Railway Safety RACOPs or Guidance Notes that support this document.

B3 Definitions Alignment The horizontal and vertical relationship between the centre-line of an element and the railway infrastructure.

Centre-line The line (usually extending out perpendicularly from the face of a signal) forming the optical axis of the beam.

Drivers’ eye level For the purposes of this document, drivers’ eye level is 2750 mm above rail level.

Driving Position The normal position from which the driver controls the train, by operating the primary controls (see GM/RT2161 for further details). Element An element of a signal is any of the following:

a) a single aspect of a main signal (a double yellow counts as two elements)

b) a position light junction indicator

c) the number/character displayed by an alphanumeric route indicator

d) a single arm/disc of a semaphore signal or, during darkness, the illuminated spectacle plate.



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e) an aspect of a position light signal.

Form of signal The combination of elements used to create a signal, and their positions relative to each other.

Lateral position The horizontal distance of a signal from the running edge of the nearest rail at a specific location on the track, and the vertical position of a signal above rail head level.

Longitudinal position The position of a signal along the track.

Normal stopping position Any position within the range of positions at which drivers are expected to stop on the approach to a signal at danger.

Permissible speed The highest permitted speed (including any enhanced permissible speed) of a train on the approach to a signal.

Platform starting signal A signal is defined as a Platform Starting Signal if either:

a) the longest passenger (or empty coaching stock) train authorised to use the platform would, if stopped at the signal, still have a portion of the passenger accommodation alongside the platform, or

b) the leading end of the train passes over the Automatic Warning System (AWS) equipment associated with the signal before it is dispatched from the station.

It is also permissible to define any other signal as being a platform starting signal where it is operationally beneficial to do so even though it does not meet the criteria above.

Readable An aspect or indication is readable if, under clear weather conditions by day and by night, persons meeting the minimum eyesight requirements of Railway Group Standard GO/RT3255 are always able to identify the aspects and indications displayed when viewed from the driving position.

Clear weather conditions means daylight visibility of 1000 m or better, where visibility is measured in accordance with guidelines such as those contained in the British Meteorological Office Observer’s Handbook.

Required reading time The required reading time is the sum of:

a) the time that is essential in order for a driver approaching a signal to:

i) identify the signal as being 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.



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B4 General requirements for

positioning and visibility of signals

This section sets out the general requirements for the positioning and optical alignment of signals to ensure that drivers have adequate visibility of signals.

The general requirements are supplemented by particular requirements for specific types of signals, in sections B5 to B9 of this document.

On a railway where driver observation of lineside signals is essential to the correct control of trains, driver cognition and response factors have the potential to introduce some significant risks. Even in the case of a perfectly positioned signal there is a finite SPAD risk.

In situations where there are particular risk factors associated with the signal (such as conspicuity problems, restricted approach view, interruptions to the view), then each of these factors constitutes a departure from the ideal and thereby increases the SPAD risk.

This document recognises that the ideal cannot always be achieved in practice. However, designing a signal to meet the absolute minimum requirements of this document when a number of these factors are present could result in intolerable risk and is to be avoided.

B4.1 Longitudinal positioning of signals B4.1.1 General requirements The longitudinal position of signals shall be selected so as to ensure that they meet the readability requirements set out elsewhere in this document, whilst also taking into account the requirements for:

a) signal spacing (see GK/RT0034)

b) the provision of signals (see GK/RT0032)

c) the positioning of signals used to control movements onto occupied lines (see GK/RT0044)

B4.1.2 Signals on parallel lines Where lines running parallel to each other are signalled in the same direction and drivers on one line can see the signal(s) on the parallel line(s), the signals for each line shall normally be placed at the same longitudinal positions as those on the parallel lines. This is called ‘parallel positioning’ of signals.

Signals shall be regarded as parallel if they are typically within five metres of each other longitudinally.

At any location where signals are provided on parallel running lines, all lines signalled in the same direction shall be equipped with a signal, except where reduced capacity bi-directional signalling is applied in accordance with GK/RT0032.

In exceptional circumstances, it is permissible not to position signals in parallel, but only where all the following conditions are met:

a) It is physically impossible to position the signals in parallel with one another (eg staggered platform ends, exit signals from yards or loops).

b) During the approach to the signals, the driver is unlikely to be confused as to the position of the signals or which signal applies to him. In particular the ‘crossing-over effect’ (in which the relative positions of the signals appears to change during the approach) shall not occur.



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c) The overrun risks associated with the non-parallel positions are acceptably low. Assessment of the risks shall form part of the process mandated by GI/RT7006.

Where lines that are operated as separate routes run parallel (eg the DC lines alongside the West Coast Main Line, or LUL lines adjacent to Railtrack infrastructure), this section applies to each route individually, and not to the set of parallel routes. Nevertheless, consideration shall be given to the risk of drivers on either route erroneously obeying signals that apply to the adjacent route.

Further references to parallel signals are contained in section B4.3.4, B4.4 and B5.4. See also Appendix 2.

B4.1.3 Train radio coverage Consideration shall be given to the adequacy of train radio coverage when positioning signals. If necessary the coverage shall be improved to suit the positioning of the signal.

B4.2 Lateral positioning of signals B4.2.1 General requirements Each signal shall be positioned laterally as follows:

a) On the left hand side of the line as seen in the direction of travel to which the signal applies, except as permitted by section B4.2.2.

b) So as to ensure that it is readable for at least the required reading time.

c) So that drivers on all lines readily associate the signal with the line to which it applies and not with any other line.

B4.2.2 Positioning of signals on right hand side of line It is permissible for a signal to be positioned on the right hand side of the line to which it applies, but only if all the following criteria are met:

a) The readability is improved for trains approaching the signal and SPAD risk is reduced.

b) The signal is readable by drivers of trains stationary in the normal stopping position at the signal.

c) There is no line immediately to the right of the signal, such that drivers on either line might associate the signal with that line rather than with the line to which it actually applies (signals on lines separated by an island platform can usually be regarded as meeting this criterion).

B4.2.3 Structural and electrical clearances Signals and signal structures shall be positioned so as to provide:

a) at least the minimum structural clearance between all parts of the signal, its associated structure and screens, and adjacent lines, including allowances for cant and track movement tolerances, using the swept envelope defined in GE/RT8029 and GM/RT2149.

b) at least the minimum electrical clearance between the signal or structure and any part of the electrification fixed equipment or the pantograph, in accordance with GE/RT8025.

B4.3 Visibility of signals B4.3.1 Readability of signals by drivers approaching a signal A signal shall be readable for no less than the required reading time (as defined in section B3) by a driver approaching on any line to which that signal applies.



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Sections B5 to B8 of this document provide specific applications of this requirement for each form of signal.

In exceptional circumstances, where it is not practicable to meet this requirement, and where re-locating the signal is either not practicable or does not improve the reading time, other measures shall be applied in accordance with section B8.

Attention is drawn to the definition of required reading time in section B3 of this document. It comprises two elements – the time that is essential in order for the driver to identify, observe and interpret the information presented, and such additional time as is reasonably practicable to provide.

B4.3.2 Readability of signals by drivers stationary at a signal A signal shall be readable by a driver in the driving position stationary at the normal stopping position. Where it is not practicable to meet this requirement, other measures shall be applied in accordance with section B8.

Section B9.1. addresses the special requirements for platform starting signals.

B4.3.3 Interruption of view So far as is reasonably practicable, there shall be no interruption of the driver’s view of a signal during the required reading time.

Where interruptions are unavoidable on the approach to a signal, then they shall not give rise to an unacceptable risk of the driver disregarding or misreading the signal (see guidance in Appendix 3). Where this is not achievable, other measures shall be applied (see section B8).

B4.3.4 Visibility of signals on other lines So far as is practicable, signals shall be aligned so as not to cause confusion in the correct observation and interpretation of other signals by drivers on other lines, whilst ensuring that a driver has adequate visibility of signals on his line.

B4.4 Consistency of form of signals Successive signals for the same direction of traffic flow shall be reasonably consistent in form in order to facilitate correct observation by the driver of the information presented.

Consideration shall be given to the form of both new or modified signals and to existing unaltered signals preceding/following the new or modified signals. The following factors shall be considered:

a) The relative position of elements of signals.

b) The choice of route indicator types.

c) The lateral position of signals.

d) The relative position of parallel signals.

It is permissible for an inconsistency of form to be introduced where this is intended to heighten a driver’s awareness of a particular signal.

B4.5 Maintainability of signalling equipment The design of the signal and associated structure shall take into consideration the proposed arrangements for the maintenance of the signal and the sighting of the signal, and shall incorporate any features necessary to allow access to the equipment for such purposes.



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B5 Colourlight main signals and associated

route indicators B5.1 Form of signals B5.1.1 Types of signals The forms of main colourlight signals (including splitting distant signals) and associated route indicators are defined in GK/RT0031. The two forms of route indicator permitted for use with main colourlight signals are the position light junction indicator (PLJI) and the standard alphanumeric route indicator.

B5.1.2 Main colourlight signals Main colourlight signal heads comprising more than one element shall usually be mounted vertically. Where necessary for visibility purposes or because of constraints on space, it is permissible to mount the elements other than in a vertical array, provided that any double yellow aspect, and any flashing double yellow aspect, continues to be displayed vertically.

If more than one element is used to display aspects, the order of proximity of lights to the driver’s eye as he passes the signal shall be as follows:

a) Red aspect light closest.

b) First yellow aspect light.

c) Green aspect light

d) Second yellow aspect light (required only for double yellow aspect and flashing double yellow aspect).

Where any of the four elements listed above are not provided, or are combined into a single unit, the order described above shall be maintained by the remaining elements.

Exceptionally, it is permissible for a signal required to show red, yellow and double yellow only to have the red light separating the two yellows, but only if the red aspect remains near driver’s eye level so that the sighting of the aspect cannot be obscured by signal hoods.

B5.1.3 Positioning of route indicators Position light junction indicators (PLJIs) shall be positioned directly above the main aspects (this refers to the pivot light). It is permissible for the indicators to be positioned immediately to the side of the main signal, but only where there is no other way of ensuring adequate readability.

Where a PLJI is positioned to the side of the main signal, the pivot light shall be positioned adjacent to the red aspect. Position indicators 1, 2 and 3 shall be placed only to the left of the main signal, and position indicators 4, 5 and 6 only to the right (but see also section B5.4.3 regarding the use of route indicators in complex areas) (see GK/RT0031 for details of position notation).

It is permissible for alphanumeric route indicators to be positioned either above, or immediately to the side of the main signal, whichever gives the optimum readability. Where an alphanumeric route indicator is positioned to the side of the main signal, it shall be positioned to the left of the main signal if the signal is on the left hand side of the line, and to the right of the main signal if the signal is to the right hand side of the line.

B5.2 Visibility requirements The requirements of this section (B5.2) apply in respect of all routes by which a train might legitimately approach a signal.



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The two heads of a colourlight splitting distant signal shall be considered as separate elements of a single signal for the purposes of complying with the requirements of this section.

B5.2.1 Required reading time The required reading time, as defined in section B3, shall be determined for each signal (except signals where trains can only start from rest, eg platform starting signals at terminal stations, for which the concept of required reading time is not applicable).

Each element of the signal shall be readable for the required reading time appropriate to that element to the driver of a train approaching on the line to which the signal applies. Section B8 provides clarification where a banner repeater or co-acting signal is used.

B5.2.2 Determining the required reading time Provision of a required reading time that equates to the minimum reading time (as defined below) is permitted only when there are no reasonably practicable measures that could be applied to provide a greater reading time.

For a signal where the risk of disregard or misread is low, the minimum reading time is a seven second time window starting eight seconds travelling time before the signal and finishing one second before the signal.

The minimum reading time shall be greater than that specified above where the probability of disregard or misread is high. Circumstances where this applies include, but are not necessarily limited to, the following:

a) The time taken to identify the signal is longer (eg because the signal being viewed is one of a number of signals on a gantry, or because the signal is viewed against a complex background).

b) The time taken to interpret the information presented by the signal is longer (eg because the signal is capable of presenting route information for a complex layout ahead).

c) There is a risk that the need to perform other duties could cause distraction from viewing the signal correctly (eg the observance of lineside signs, a station stop between the caution and stop signals, or DOO (P) duties).

d) The control of the train speed is influenced by other factors (eg significant changes in gradient, or anticipation of the signal aspect changing).

Guidance on minimum reading times is given in Appendix 2.

required reading time

Not less than7 seconds

(see section B5.2.2 for detailsof where greater times are

mandatory)

1 secondadditional time which it is reasonablypracticable to provide

Direction of travel

minimum reading time

Figure B5.2.2



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B5.2.3 Calculating the location at which the required reading time commences The location on the train’s approach to the signal at which the required reading time commences shall usually be calculated using the permissible speed applicable at that location. It is from this location onwards that the signal has to be readable (see section B4.3.1).

Where the maximum attainable speed of all trains using the route is less than the permissible speed, it is permissible for the infrastructure controller to authorise the use of the attainable speed in calculating the location at which the required reading time commences.

Where a junction signal is approach controlled from red, it is permissible for the required reading time of the route indication (but not of the main signal itself) to commence at a location which is nearer the signal, based on the speed profile of the train as it approaches the signal at danger. The signal shall be released from danger at a location where the main signal and the associated indication are both readable by the driver (see GK/RT0032).

B5.2.4 Close-up viewing of the signal All elements of the signal shall be readable from the driving cab with no interruption of view between:

a) a point that is the greater of 40 m or the distance equivalent to one second’s travelling time from the signal (at the permissible speed)

b) the closest point at which a driver would be expected to bring his train to a stand at the signal at danger.

Where the signal is fitted with a device that offers a means of enhanced close-up viewing (for example a ‘hot strip’) the device shall be orientated to optimise the readability over this distance.

The purpose of these requirements is to ensure that the driver has an adequate view when he is bringing his train to a stand at the signal, and when he is stationary in the normal stopping position. B5.2.5 Alignment of signal The signal shall be aligned so as to optimise the readability of the signal by the driver of an approaching train, taking into account the need for all illuminated elements of the signal to:

a) be readable at the start of the required reading time

b) remain readable throughout the required reading time.

B5.3 Lateral position of signal B5.3.1 Height of signal above rail level Except as permitted below, the centre of the element that displays the most restrictive element shall be as close as possible to, but not less than, 3.3 m above rail level.

Where necessary to provide adequate visibility, it is permissible for the most restrictive element of the signal to be up to 5.1 m above rail level. In deciding whether it is acceptable to use a height greater than 3.3 m, attention shall be given to:

a) the difficulty that a driver might have in relating the signal to the line to which it applies (especially where the approach to the signal is curved, with signals on parallel lines)

b) the readability of the signal during the driver’s approach (see section B5.2.5)



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c) the readability of the signal when the driver is close to it (see section B5.2.4)

d) possible problems with incident or background sunlight, or with the background against which the signal is viewed, preventing the aspect from being discerned

e) the risk of reading through to another signal ahead, instead of obeying the correct signal.

It is also permissible, where necessary to provide adequate visibility, or because of space constraints, for a signal to be positioned with some or all of its elements below 3.3 m. In deciding whether it is acceptable to position a signal below the height specified in this section, particular attention shall be given to:

f) the readability of the signal during the driver’s approach (see section B5.2.5)

g) lines where the driver’s eye level on all trains is lower (eg LUL stock)

h) the readability of the signal when the driver is close to it (see section B5.2.4)

i) risk of obscuration of the signal (eg by the signal head hoods, signs, persons on the track)

j) the presence of a co-acting signal.

B5.3.2 Horizontal displacement of signal relative to rails Signals to the side of the structure gauge (eg post mounted) shall be positioned as close as possible to the nearest running rail of the line to which they apply whilst still maintaining clearances as specified in GE/RT8029.

Signals above the structure gauge (eg gantry or cantilever mounted) shall usually be positioned with the centre line of the most restrictive aspect approximately 900 mm to the left of the running edge of the left-hand rail. It is permissible for such signals to be positioned further to the right, (but not to the right of the track centreline) if by doing so:

a) the readability throughout the required reading time is improved, or

b) the association of the signal with the correct line is improved.

B5.4 Parallel signals B5.4.1 Identification of lines On parallel lines signalled in the same direction, consideration shall be given to the provision of a means by which a driver can more readily identify the signal that is applicable to the train. This is particularly important on lines with three or more parallel signals, or where a junction is unusually complex.

Measures to be considered (singly or in combination) include:

a) staggering the heights of parallel signals within limits of section B5.3.1 (where this is done on sets of signals, the stagger arrangements shall be applied consistently at all the sets)

b) the use of route indicators on all signals (including straight routes) so that a driver is always given information regarding the line on which the next signal is to be found

c) the use of line identifiers (see section B10.6) to identify which signal applies to the driver.



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B5.4.2 Signal structures Consideration shall be given to the advantages, from a driver’s perspective, of consistency in the type of structures on which successive parallel signals are mounted. The inconsistent use of gantries, cantilevers and straight posts for successive groups of parallel signals can contribute to the misreading of signals by drivers.

B5.4.3 Route indications Route indicators shall give drivers clear and unambiguous indications of the route set.

Where it is proposed to provide PLJIs on parallel signals, consideration shall be given to the risk of driver confusion caused by:

a) the same position indication (1-6) applying to different destinations depending on which signal the indicator is associated with (complex junctions may be particularly at risk)

b) the route indicator being associated with the wrong main signal (indicators mounted to the side of a main aspect may present a particular risk).

See GK/RT0031 for details of PLJI position notation.

B6 Position light signals and associated

route indicators B6.1 Form of signals The form of position light signals (PLS) and associated route indicators is defined in GK/RT0031.

Except as permitted below, subsidiary PLSs shall be positioned immediately below the red main aspect. It is permissible for the subsidiary PLS to be positioned immediately to the left of the main red aspect when the signal is to the left of the line to which it applies, or to the right if the signal is to the right of the line to which it applies, if:

a) route indicators are associated with the PLS, or

b) the effect of placing the PLS beneath the red aspect would be to make the red aspect less readable, because of its increased height.

Where route indicators are associated with a subsidiary or independent PLS, they shall usually be positioned immediately above the PLS.

Other forms shall only be used where conflicts with B5.1.3 might occur, or where gauge restrictions exist.

B6.2 Visibility requirements B6.2.1 Required reading time The following types of PLS shall meet the visibility requirements set out in sections B5.2.1, B5.2.2 and B5.2.4:

a) Independent PLS.

b) Subsidiary PLS cleared for a shunting movement.

The location at which the required reading time commences shall be calculated using the permissible speed applicable to the train movement.

In addition to meeting the requirements of sections B5.2.1 and B5.2.2, the required reading time for an independent PLS shall be sufficient for a driver to brake to a stand at the signal from the permissible speed applicable to the train



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movement (this is not applicable to independent PLSs where trains can only start from rest).

A subsidiary PLS used only for controlling movements onto an occupied line (ie. not for shunting movements) shall meet the visibility requirements set out in section B5.2.4. See also GK/RT0044.

The requirements in this section are not applicable when an independent PLS acts as a preset shunt signal.

B6.2.2 Alignment PLSs and associated indicators shall be aligned towards a train standing at the normal stopping position on the approach side of the signal. This requirement is subordinate to reading time requirements set out in section B6.2.1.

B6.3 Lateral position of independent PLSs B6.3.1 Height of signal above rail level Due to structure gauge constraints, independent PLSs shall usually be positioned with the top of the signal, including any route indicator, no more than 914 mm above rail level. Where necessary to improve visibility or to achieve structural clearance, it is permissible to position independent PLSs at greater heights, subject to a maximum of 5.1 m. In deciding whether it is acceptable to use a height greater than 914 mm, attention shall be given to:

a) the difficulty that a driver might have in relating the signal to the line to which it applies (especially where the approach to the signal is curved and there are signals on parallel lines)

b) the readability of the signal on the approach to it

c) the readability of the signal when the driver is stationary at it

d) possible problems with incident or background sunlight, or with the background against which the signal is viewed, preventing the aspect from being discerned

e) the risk of reading through to another signal ahead, instead of obeying the correct signal.

f) the risk of an overrun due to disregard, because of the unusual height

B6.3.2 Horizontal displacement of signal relative to rails Independent PLSs shall be positioned in accordance with the requirements of section B5.3.2.

B7 Semaphore signals and signs that perform the function of signals

B7.1 Form of signals and signs B7.1.1 General requirements The form of semaphore signals (main, shunting and subsidiary types), stop and distant boards is defined in GK/RT0031.

In meeting the requirements of this document, all semaphore signal arms, discs and indicators mounted on a common structure and applying to the same line shall be treated as elements of a single signal.

Arms shall be of the upper quadrant type unless existing signals at that location are wholly or largely lower quadrant. All arms on a structure shall be of the same type.



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Colourlight and semaphore elements shall not be intermixed on a signal except that it is permissible to use alphanumeric route indicators in conjunction with semaphore stop signals.

Semaphore shunt signals shall be of the disc type unless existing shunt signals at that location are wholly or largely miniature arm type.

B7.1.2 Signals with multiple arms Where multiple routes exist from a main signal a separate arm shall be provided for each route, arranged horizontally. The position of each arm from left to right shall correspond to the direction of the route from left to right. Routes which differ in speed shall be stepped in height; the highest arm shall apply to the fastest route and subsequent arms to either side shall be progressively lower. The dolls shall be a minimum of 1830 mm apart and the arms stepped in height by a minimum of 760 mm increments.

The following alternative forms of junction signal are permitted if their use improves clarity or consistency:

a) Junction signals arranged with multiple routing arms arranged vertically above one another. The position of each arm from top to bottom shall correspond to the direction of the route from left to right. Arms shall be a minimum of 1680 mm apart. This arrangement shall be used only where the speed differential between the fastest and slowest route is no greater than 10 mile/h and where the permissible speed is no greater than 40 mile/h.

b) Junction signals arranged with a single arm and a standard alphanumeric route indicator positioned directly underneath. Consideration shall be given to the risk of a bright route indicator obscuring a relatively dim signal lamp.

Where stop and distant arms applying to the same route are to be mounted on the same post the distant arm shall be positioned 1680 mm (+/- 200mm) below the stop arm.

Where stop and subsidiary arms applying to the same route are to be mounted on the same post, the subsidiary signals shall be fitted 1070 mm (+/- 200mm) below the arm next above. Where a distant signal is fitted below a stop signal, any subsidiary signal shall be fitted below the distant signal arm.

The discs / arms of shunting signals shall be arranged directly above one another and their positions from top to bottom shall correspond to the direction of the route from left to right. Where more than one disc / arm is mounted on a single structure, all such discs / arms shall be of uniform type (ie all discs or all arms), size and design. Where arms are used, they shall be spaced 1070 mm (+/- 200 mm) apart.

B7.1.3 Lighting of semaphore signals Except as permitted below, the light intensity of all main semaphore signals shall be reasonably consistent within the area controlled by a signal box.

It is permissible for the light intensity of a semaphore signal to be significantly greater than that of other signals controlled by the same signal box, if by doing so it improves the readability of that signal and does not increase the likelihood of drivers misreading or disregarding other signals.

B7.2 Visibility requirements B7.2.1 Main signals A main semaphore signal shall meet the visibility requirements set out in sections B5.2.1 to B5.2.4 inclusive. The requirements apply to both the day and night indications of the signal.



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B7.2.2 Shunting and subsidiary signals The following types of semaphore shunting and subsidiary signals shall meet the visibility requirements set out in sections B5.2.1, B5.2.2 and B5.2.4:

a) Independent shunting signal.

b) Subsidiary signal cleared for a shunting movement.

The requirements apply to both the day and night indications of the signal.

The location at which the required reading time commences shall be calculated using the permissible speed applicable to the train movement.

In addition to meeting the requirements of sections B5.2.1 and B5.2.2, the required reading time for an independent shunting signal shall be sufficient for a driver to brake to a stand at the signal from the permissible speed applicable to the train movement (this is not applicable to independent shunting signals where trains can only start from rest).

A subsidiary signal used only for controlling movements onto an occupied line (ie. not for shunting movements) shall meet the visibility requirements set out in section B5.2.4. See also GK/RT0044.

The requirements in this section are not applicable when an independent shunting signal acts as a preset shunt signal.

B7.2.3 Signs Signs that perform the function of a signal shall meet the visibility requirements set out in sections B5.2.1 to B5.2.4 inclusive. The requirements apply to both the day and night indications of the sign.

The sign (but not necessarily any wording on it – see GK/RT0031) shall be readable by the driver for the required reading time.

B7.3 Lateral positioning B7.3.1 Main and subsidiary signals The centre of the lowest element of the signal shall be as close as practicable to, but not below, driver’s eye level, except as permitted below.

Where essential to provide adequate visibility, it is permissible for the signal height to be increased. In deciding whether it is acceptable to use a greater height, attention shall be given to:

a) the difficulty that a driver might have in relating the signal to the line to which it applies (especially where the approach to the signal is curved, with signals on parallel lines)

b) the readability of the signal when the driver is close to it

c) the risk of reading through to another signal ahead, instead of obeying the correct signal.

It is permissible for subsidiary shunting signals to be ground mounted.

B7.3.2 Shunting signals Semaphore disc signals shall usually be positioned with the top of the signal no more than 914 mm above rail level. It is permissible to elevate disc signals or miniature arm signals where necessary to improve viewing or gain structural clearance, but in no case shall this be greater than 5.1 m above rail level.



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B7.3.3 Signs Stop and distant signs shall normally be positioned laterally as close as possible to the nearest running rail of the line to which they apply whilst still maintaining clearances as specified in GE/RT8029.

The horizontal centre of the distant board or the red target of a stop board shall usually be positioned 2.5 m (+/- 0.1m) above rail level.

B8 Use of banner repeating and co-acting

signals B8.1 Measures to address problems of inadequate visibility of signals It is not always practicable to achieve the visibility requirements for main signals by appropriate positioning and alignment of the signal. Where this is so, it is permissible to apply alternative measures in order to ensure that the driver does have adequate time to observe and assimilate signal aspect and routing information. These measures include:

a) the use of banner repeaters (see section B8.2)

b) the use of co-acting signals (see section B8.3)

c) applying a reduced permissible speed on the approach to the signal (such a reduction shall apply for no less than the distance that equates to the required reading time, calculated at the reduced permissible speed).

B8.2 Banner repeater signal B8.2.1 Form of banner signal The form of banner repeater signals (including splitting banner repeater signals) is defined in GK/RT0031. This section deals with banner repeaters, not miniature banner repeaters used on platforms for train dispatch purposes (see section B9).

Banner repeaters provide only limited information about the aspect of the signal ahead, which in turn restricts their usefulness as a means of improving the reading time of main signals. Their value, in the context of signals with poor visibility, is in alerting the driver to the fact that he is approaching a signal, thus maximising his use of the reading time associated with that signal. However, it is always preferable to improve the visibility of the main signal where this is reasonably practicable, rather than providing a banner repeater.

Banner repeater signals shall not be provided to repeat a signal capable of displaying flashing yellow or splitting distant aspects.

B8.2.2 Visibility requirements for banner signals Where a banner signal is provided, the arrangement shall be that:

a) the combined reading times of the main and banner signals is not less than the required reading time of the main signal, and

b) both the main and banner signals shall as a minimum each be readable by the driver for a four-second time window starting five seconds from the signal (calculated at the permissible speed).

Usually the main signal shall become visible when the driver loses sight of the banner repeater. However, it is permissible to have a gap between losing sight of the banner signal and the main signal coming into view, if the effect is to significantly increase the total reading time. The gap shall be as brief as possible, subject to achieving good sighting of the banner signal, (typically no more than three seconds).



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B8.2.3 Lateral position of banner signal The requirements of section B5.3 shall be applied to determine the lateral position of a banner signal.

B8.3 Co-acting signals B8.3.1 General requirements It is permissible to use co-acting signals with both colourlight and semaphore signals. Where a co-acting signal is provided, the signal that is nearest to the usual position for a signal shall be defined as the primary signal.

Co-acting signals shall not be provided where the primary signal is a splitting distant.

B8.3.2 Form of co-acting signal The co-acting signal shall be of the same style (colourlight or semaphore) as the primary signal.

The main aspects/arms of the co-acting signal shall be the same as those of the primary signal. It is permissible for subsidiary aspects/arms and indications associated with the primary signal to be repeated by the co-acting signal if required.

B8.3.3 Positioning of co-acting signal The longitudinal position of the co-acting signal shall be no more than 2 m from the primary signal.

The lateral position of the co-acting signal shall be such that there is no possibility of a driver mistakenly thinking that it applies to another line.

It is permissible for the co-acting signal to exceed the minimum or maximum height requirements set out elsewhere in this document, where necessary to provide adequate visibility.

B9 Platform equipment B9.1 Position and visibility of signals on platforms B9.1.1 Visibility of platform starting signals for drivers All elements of a signal designated as a platform starting signal shall usually be readable by a driver in the driving position of any train authorised to use the route, from all normal stopping positions of trains at the platform. Where this is impracticable, banner repeaters shall be provided which are readable from the normal stopping positions. Where permissible speeds allow, miniature banner repeaters meeting performance category 3 of GK/RT0031 (or, as a non-preferred option, OFF indicators) can be used.

B9.1.2 Lateral position of signals on platforms Where signals on platforms are positioned below the normal height (see sections B5.3.1 and B7.3.1), specific consideration shall be given to the risk of elements being obscured by people on the platform, as well as to other factors associated with signals positioned below the normal height.

It is permissible for miniature banner repeater signals to be positioned to the right of the line to which they apply if the platform is on the right hand side and they are readable from the associated stopping position(s).

B9.2 Train dispatch equipment B9.2.1 Switches and plungers Switches or plungers required for Train Ready To Start (TRTS), Right Away (RA) or Close Doors (CD) functions on a platform shall be co-located and shall be positioned where staff carrying out train dispatch duties can adequately observe the train they are dispatching.



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Where platforms are bi-directional or have mid-platform signals the layout and labelling of the switch/plunger units shall be such as to minimise the risk of operation of the wrong switch/plunger.

It is permissible for duplicate switch/plunger units to be provided where more than one dispatch position is required.

B9.2.2 OFF indicators OFF indicators shall be provided in situations where train dispatch staff are unable to see the platform starter signal or banner repeater from all designated dispatch positions. They shall be positioned so as to be readable by the dispatch staff from the dispatch position(s).

A banner repeater signal is not a suitable substitute for an OFF indicator if it is replaced to danger by occupation of the signal berth track circuit.

Where OFF indicators are provided on bi-directional platforms or platforms equipped with mid-platform signals, the OFF indicator shall additionally indicate the signal or direction of movement to which it applies.

B9.2.3 CD / RA indicators CD and RA indicators, where required, shall meet all of the following requirements:

a) Be co-located with the platform starting signal and with any banner repeaters (see section B9.1.1).

b) Be positioned such that they are readable by the driver when stationary at any normal stopping position.

c) Where possible, be positioned such that they are readable by the dispatch staff.

B9.3 Train stopping positions No car stop marker or DOO monitor unit shall be positioned such that a train is required to stop within 25 m of the platform starting signal, except as permitted below.

It is permissible for the normal stopping position of a train to be within 25m of the platform starting signal where the signal is sufficiently conspicuous such that a driver in the driving position is aware of the aspect displayed while looking at the route ahead. Where there is doubt as to whether this is achievable, consideration shall be given to the use of additional control measures to reduce the likelihood or consequence of a SPAD. Such measures include, but are not limited to:

a) use of RA indicators as part of the train despatch process

b) a train protection system to stop trains short of any area of conflict (as defined in GI/RT7006)

c) a suitably positioned co-acting signal.

B10 Miscellaneous technical requirements

B10.1 Colour of structures and fittings The colours usually applied to signal structures and fittings are described in GK/RT0031. It is permissible to paint signal structures in a distinctive colour to aid drivers in locating a signal, and the line to which it applies, in a complex area. Permitted arrangements are:

a) black for the horizontal part of a gantry or cantilever, where this will distinguish it from other structures that are coloured grey (eg OLE)



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b) white and black hoops for a post.

Overuse of such a measure can render it ineffective.

B10.2 Rear of signal indicators Rear of signal indicators (for drivers where the driving cab is ahead of the signal applicable to them) shall only be provided in exceptional circumstances, where a signal cannot be positioned so as to be visible from the cab of the longest train expected. In selecting the indications to be displayed by such a signal, the risk of the indications being misinterpreted either by the intended driver or by the driver of another train shall be considered.

Rear of signal indicators shall be positioned in close proximity to the signal to which they apply, such that the relationship between the two is clear. Their form shall be in accordance with GK/RT0031.

B10.3 Countdown markers It is permissible to provide countdown markers, as shown in GK/RT0033, on the approach to signals where this is felt to be beneficial.

Such markers shall be provided as a sequence of three signs, positioned 100 m apart with the last one 100 m before the signal. Other arrangements are permissible where it is considered that this will be of greater benefit to the driver.

The use of countdown markers shall usually be determined as part of the risk assessment process required by GI/RT7006.

Overuse of countdown markers can render them ineffective.

B10.4 Signal reminder signs It is permissible to provide a signal reminder sign on the approach to signals where there is a significant risk of a driver forgetting that he is approaching a signal at danger (eg due to distractions after passing the previous signal at caution, such as a station stop).

The positions of such signs shall be selected on a site-specific basis such that the driver, having been reminded, can take action to stop at the signal.

The use of signal reminder signs shall usually be determined as part of the risk assessment process required by GI/RT7006.

Overuse of signal reminder signs may render them ineffective.

B10.5 Sighting boards, hoods and blinds B10.5.1 General requirements It is permissible for sighting boards, extended hoods or vertical blinds to be used where it will improve the readability of signals under some or all ambient lighting conditions. The effect shall be assessed to avoid any reduction in readability from any driving position of the driver of a train approaching the signal.

Consideration shall be given to the need to ensure that such measures do not degrade the readability of other signals in the area.

Consideration shall be given to masking a source of interference where this is more readily achieved. B10.5.2 Sighting boards The use of sighting boards is permitted where the readability of a signal under some or all lighting conditions could be improved by increasing the contrast against the background. The colour as seen by an approaching driver shall usually be black for colourlight signals and white for semaphore signals.



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The board shall be positioned so as to appear directly behind the signal when seen by an approaching driver. The size shall be determined to suit local circumstances.



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B10.5.3 Hoods The use of long hoods is permitted to shield the aspects from sunlight or other light sources. The assessment required in section B10.5.1 shall particularly consider the risk of hoods obscuring other elements.

B10.5.4 Blinds The use of blinds is permitted to shield a signal from being read by a driver on another line.

B10.6 Line identifiers B10.6.1 Form and use of line identifiers The use of line identifiers is permitted on parallel lines where this will reduce the risk of confusion as to which signal applies to which line. Where line identifiers are used they shall be applied to all parallel lines, numbered or lettered in a fashion that is logical to drivers, and positioned in a consistent manner. They shall be positioned so as to be visible to drivers as follows (one or more than one of the arrangements can be applied):

a) Alongside the signals.

b) On the rear of gantries carrying signals for opposite direction movements, or on other structures.

c) Between the running rails, in the area known as the ‘four foot’.

d) On posts.

The use of line identifiers shall usually be determined as part of the risk assessment process required by GI/RT7006.

B10.6.2 Application of line identifiers when alphanumeric route indicators are also in use Where alphanumeric route indicators are also in use, the characters for the line identifiers shall be the same as those displayed by the route indicators (ie the route indicators shall indicate the line identifier character for the line on which the next signal is to be found).

B10.7 SPAD indicators The form of SPAD indicators is defined in GK/RT0031.

The SPAD indicator shall be aligned and positioned so as to:

a) maximise the likelihood of an unauthorised movement being brought to a stand before reaching any point of conflict

b) where indicators are provided at more than one conflicting signal, to bring authorised movements to a stand in the event of a SPAD being detected at another signal.

The use of a co-acting indicator is permitted if conflicts arise in meeting these requirements.

B10.8 Point indicators and crossing indicators The form of point indicators and crossing indicators (including barriers up indications) is defined in GK/RT0031.

Visibility requirements shall be as described in section B5.2 so far as they are applicable.

The lateral position shall be as described in section B5.3.



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B10.9 Anti-vandalism measures The readability of a signal shall not be affected by any anti-vandalism measures applied to the signal.

B11 Signal sighting process

Signal sighting shall be undertaken by a committee convened specifically for that purpose, and shall take place sufficiently early in a scheme that the options available to a committee to optimise the readability of signals are not restricted by actions or decisions already made.

B11.1 Concept design stage requirement As a part of the signalling design production and overrun risk assessment processes (see GK/RT0207 and GI/RT7006 respectively), as much detail as possible about the proposed position and form of each new and altered signal (and each indicator and sign performing the function of a signal) shall be produced during the concept design phase. Consideration shall be given to the use of computer/video simulation or reproduction techniques to carry out the requirements of this section.

These details shall be submitted to a signal sighting committee in order for an on-site evaluation of the proposals to be undertaken.

B11.2 Role of signal sighting committees The infrastructure controller shall ensure that a signal sighting committee verifies the proposed position and form of all new, modified and re-positioned signals, indicators and signs that perform the function of signals. The committee shall:

a) review the proposed sighting details in conjunction with a scheme plan produced by the designers

b) make recommendations regarding those details not already provided by the designers

c) make recommendations regarding details provided by the designers that require amendment.

When satisfied, each committee member shall sign to indicate their agreement with the proposed sighting details, and the committee shall recommend the sighting details for approval by the infrastructure controller (see section B11.6).

B11.3 Additional responsibilities of the signal sighting committee A signal sighting committee shall also be required to consider the positioning of the following items of infrastructure equipment:

a) Signal post telephones – see GE/RT8048.

b) Permanent speed indicators – see GK/RT0038.

c) AWS magnets – see GE/RT8035.

B11.4 Committee membership A signal sighting committee shall consist of persons who have the collective competence for determining the train driver, station dispatcher and engineering requirements appropriate to each signal under consideration. The committee shall include:

a) Representatives of the infrastructure controller, with both operations and engineering experience.

b) A representative of the signalling scheme design organisation.



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c) One or more representatives of train operating companies (both TOCs and FOCs) operating over the route, with experience in driving the relevant types of trains.

d) One or more representatives of station operating companies on the route, if the signals under consideration include platform starting signals.

The committee shall be led by a chairman, appointed and approved in advance by the infrastructure controller.

When extensive signalling work is being undertaken involving the provision or modification of large numbers of signals consideration shall be given to the inclusion of specialist human factors expertise within the signal sighting committee.

B11.5 Signal sighting committee competencies B11.5.1 General requirements The infrastructure controller shall ensure that, collectively, the signal sighting committee possesses all the following:

a) All necessary competencies (see sections B11.5.2 – B11.5.4).

b) Sufficient local knowledge for the route and signals under consideration.

c) A working knowledge of the requirements of this document, and of other associated documents and sources of information (eg gauge requirements).

B11.5.2 The choice, position and visibility of the signal The signal sighting committee shall be collectively competent to make recommendations concerning:

a) form of new or modified signals

b) longitudinal and lateral position of each signal

c) the reading time for each signal (including the acceptability of any interruptions)

d) alignment and close-up viewing requirements for each signal

e) special measures for overrun risk control (see sections B8 and B10)

f) train despatch arrangements from platforms and associated train despatch equipment (see section B9)

g) arrangements for maintainability of signals.

B11.5.3 Factors for consideration relating to overrun risk The signal sighting committee shall be collectively competent to consider the effects of the following factors on the likelihood of an overrun occurring:

a) Gradients and permissible/attainable speeds.

b) Preceding aspect sequences and route indications, including those of existing signals.

c) Routes by which a driver could approach a signal.

d) Grouping of parallel signals and the potential for drivers to be confused as to which one applies to the line they are on.

e) Train working arrangements (including running and shunting movements, and movements onto occupied lines).



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f) Normal stopping positions of trains.

g) Train despatch arrangements.

h) Complexity of infrastructure (eg station areas, overhead line equipment, curved approaches, bridges).

i) Types of trains authorised or planned to operate over the route and in particular their cab sight lines (see also GM/RT2161).

j) Irregular spacings of signals.

k) Potential driver distractions (eg station stops, speed restrictions; neutral sections).

l) Ambient lighting conditions (including effects of sunlight on signal head).

m) Effects of artificial lighting (reflected and background).

n) Reading through to other signals.

o) Signals unusually positioned (eg on right hand side of line).

p) Position of AWS in relation to signal (see GE/RT8035).

q) Train radio coverage.

B11.5.4 Other issues for consideration The signal sighting committee shall be collectively competent to consider the following issues:

a) Structure gauge, clearances and other matters related to the infrastructure and proposed signal structures, including any alterations to the infrastructure that are planned to take place during the works.

b) The compatibility of signals and electric traction equipment, for example any conflicts between the positions of neutral sections and the positions of signals (see GK/RT0032), and potential interruptions to visibility (see Appendix 3).

c) Local problems or special conditions, for example, a previous history of overruns in the vicinity; driver’s complaints regarding the approach view; areas of high vandalism; signs with the potential to obstruct signal visibility.

B11.6 Approval of committee recommendations The sighting details as recommended by the signal sighting committee shall be approved by the infrastructure controller when satisfied that the recommendations are adequate to control the risk of an overrun (SPAD).

Where the infrastructure controller does not approve the recommendations, the signal sighting committee shall be reconvened to review the previous proposals and propose appropriate alternative arrangements. The infrastructure controller is not permitted to approve any sighting details unless they are supported by the sighting committee (as indicated by the signature of the members – see section B11.2).

Signal sighting details shall be approved before the production of engineering details commences (except as permitted by GK/RT0207).

B11.7 Review of overrun risk assessment Where the form or position of a signal, as proposed by the designers, is subsequently altered as a result of the signal sighting committee’s



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recommendations, the relevant parts of the overrun risk assessment (mandated by GI/RT7006) shall be reviewed to ensure that the assessment is still valid.

B11.8 Commissioning checks The requirements for the testing and commissioning of signals are set out in GK/RT0209. The tests shall include:

a) A compliance check of the installed signal against the approved sighting details.

b) An adequacy check to ensure that the driver’s view is adequate to reliably identify and observe the signal and correctly interpret the signalling information.

The adequacy check shall be carried out from the driving cab using rolling stock appropriate to the line of route or from the track using a periscope or equivalent device. If it is not practicable to observe every aspect combination from all possible approaches, a representative sample of all combinations shall be observed, selecting where possible for this sample those giving the greatest potential for misreading or incorrect driver response. The most restrictive aspect shall always be observed from all possible approaches.

Where practicable, these checks shall be conducted before the signals are brought into service. Where this is not practicable, it is permissible for the checks to be carried out (or completed) within the seven days after the signals are brought into service.

B11.9 Post-commissioning checks The infrastructure controller shall ensure that consultation is arranged with drivers to identify any problems or concerns about the sighting of signals that have become apparent by day or night after the introduction of the new or altered signals. Consultation shall be completed no later than three months after commissioning.

Any remedial actions identified between bringing the signals into service and the drivers’ review shall not be delayed awaiting the results of the review.

Any remedial actions shall be implemented on a timescale agreed by the infrastructure controller and train operator(s), commensurate with the risks. Where necessary, special measures shall be applied to control the risk pending the implementation of the remedial actions.

B11.10 Equipment used for signal sighting purposes Video equipment, computer systems and tools used to support signal sighting activities shall comply with the requirements of section B11 of GK/RT0207.

B12 Records B12.1 Information to be retained A record shall be created for each signal. It shall contain, as a minimum:

a) all the current approved sighting details together with details of the modification history of the signal, including any changes or additions that affect its position, appearance, alignment point or light output (a typical signal sighting form is provided in Appendix 1)

b) a record of the approval by the infrastructure controller (see section B11.6)

c) details of assessments, calculations, assumptions and justifications associated with the chosen form, position and alignment of the signal

d) reports of problems with the sighting of signals, including those raised at the post-commissioning consultation (see section B11.9)



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e) dated photographs of the signal at commissioning and after any alterations. As a minimum, two views of each signal shall be required, one from the location corresponding to the start of the required reading time, and a second close to the signal, showing clearly the arrangement of the signal elements

f) details (eg in diagrammatic form) of any partial or complete obstructions to the driver’s viewing of signals that occur within the required reading time.

GI/RT7001 sets out the general requirements for infrastructure records.

B12.2 Availability of information Records of signals shall be accessible for the purposes of:

a) investigating sighting complaints (see GI/RT7006)

b) overrun investigations (see GO/RT3252)

c) planning alterations to signalling

d) maintenance and visibility checks (see GE/RT8034).



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APPENDIX 1

Examples of a Typical Signal Sighting Form (The contents of Appendix 1 are advisory and not mandatory)

Example One – Page One



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Example One – Page Two



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Example Two - Page One



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Example Two - Page Two



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APPENDIX 2

Guidance on Minimum Reading Time (The contents of Appendix 2 are advisory and not mandatory)

2.1 General guidance

The required reading time is that which is determined as being both necessary and reasonably practicable to provide (see definition in section B3).

The provision of significantly extended reading times in order to control SPAD risk should be treated with caution, and wherever practicable the identified risks should be removed or minimised rather than relying on increased reading time.

There will, however, be signals where the required reading time has to be extended because of their complexity, or the complexity of the surrounding infrastructure upon approach to the signal, or because of distractions between the warning signal and the stop signal.

An additional allowance of one or two seconds should be adequate for most of the individual situations identified below. Where a signal manifests more than one such situation, a greater allowance will be required.

Required reading times should, of course, never be so great that a driver is expected to start observing one signal before he has passed the previous signal (in practice this is very unlikely to arise).

At the time of publication of this document, research work is in progress to support the development of further rules for increased reading times, based on a better understanding of the relevant human factors issues.

Attention is drawn to the definition of required reading time (see section B3), in that it incorporates not only that time which is necessary for the driver to identify, observe and interpret the information conveyed by the signal (as described above), but also such additional time as is reasonably practicable to provide.

2.2.1 Single complex signal Additional reading time may be needed where a signal consists of many elements or is capable of displaying complex or unusual combinations of indications. The following is a list of likely arrangements where additional reading time should be considered:

a) PLJI positions 2,3,5 or 6 are provided.

b) Splitting distant or splitting banner signals.

c) Unusually large number of elements.

d) Unusual configuration of elements (eg horizontal aspects or PLJI to the side of the signal).

2.2.2 Multiple parallel signals It is known that where multiple parallel signals exist, drivers sometimes identify the signal relevant to their line by counting across from left or right. An additional time allowance may be needed to cater for this process. Where parallel signals do not become visible at the same time or have variable interruptions to their view, there is an increased risk of drivers misreading which signal to obey. The additional time allowance therefore should permit drivers to correctly identify all parallel signals, select the signal applicable and act on the aspect/indication displayed.



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2.2.3 Significant rising or falling gradient On a significant rising gradient a driver may be concentrating on maintaining speed thereby forgetting the aspect of the caution signal he has already passed. Additional reading time of the stop signal may allow a driver to recover from such an error without passing the signal at danger.

Similar risks may exist on significant falling or change in gradient approaching the signal.

2.2.4 Change in permissible speed An increase in permissible speed positioned between the caution and stop signal may cause a driver to forget the caution aspect and apply power to accelerate. Additional reading time of the stop signal may allow a driver to recover from such an error without passing the signal at danger.

A decrease in permissible speed may also be considered where the braking curve for the speed restriction is similar to, but not as severe, as braking for the signal.

2.2.5 Accelerating away from a station In addition to the risk of passing the platform starting signal at danger there is a risk created when the platform starting signal is at caution and the aspect is forgotten as a result of train despatch activities. If the departing train has still to pass the station starting signal AWS, the risk is considered to be low, otherwise additional reading time of the signal at danger may allow a driver to recover from such an error without passing the signal at danger.

A calculation may be carried out to determine if a train accelerating from rest at the station could stop at the danger signal if braking was applied where the signal first became readable.

2.2.6 Lineside distractions or driver task demands SPADs are known to occur as a result of drivers being distracted by features or activities at the lineside or by other duties such as DOO(P) operation or traction voltage changeover. If this distraction occurs at the caution signal or between the caution and stop signals there is an increased risk of the driver forgetting the caution aspect or failing to control the train’s speed adequately. Many examples of distractions have been identified as being outside the railway. If the source of the distraction cannot be removed or hidden, increased reading time may minimise the consequences of the distraction.

2.2.7 Where a driver might anticipate signal aspects changing SPADs are known to occur where drivers regularly experience aspects stepping up, and are therefore liable to anticipate that this will occur every time. Increasing the reading time on the stop or caution signal may be considered appropriate if other means to prevent the anticipation are not practicable.

2.2.8 Signals on curved approaches Parallel signals with curved approaches create a particular risk of misread if one or more of the following situations exist:

a) Signals on other lines are initially more visible to a driver than the signal applicable.

b) The signals become visible at different times on the approach.

c) Signals are obscured by other trains.

2.2.9 Signal seen against a complex background The time to identify a signal may need to be increased where the signal is seen against a background that is complex or contains light sources similar to signal aspects. An enlarged sighting board may be a suitable alternative option.



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APPENDIX 3

Guidance for Assessing Interruptions to View (The contents of Appendix 3 are advisory and not mandatory)

This Appendix provides guidance on the acceptability of interruptions to the driver’s view of a signal. However, preference should always be given to the elimination of interruptions where it is reasonably practicable to do so.

3.1 Items that can be exempted For the purposes of all sections in this appendix, any item whose presence in the driver’s line of sight has no noticeable effect on the appearance of the signal elements displayed may be exempted when considering interruptions to the view. An item causing a signal element to be obscured by no more than 10% of its surface area would usually meet this description.

Examples of items that can usually be exempted:

a) Catenary and contact wires.

b) Headspan and cross span wires.

c) Registration arms.

d) Return conductors.

Exemption of items such as those above should be reconsidered if changes to the design of the overhead line equipment make this appropriate.

Where these items occur in such quantities that, considered together, they obscure signal elements by more than 10%, they cannot then be exempted for the purposes of this section.

3.2 Interruptions to view Interruptions to the driver’s view of a signal generally become more critical the closer that the driver is to the signal. In sections 3-2.1 to 3-2.3 of this appendix, the three zones referred to are as depicted in the diagram below, and the guidance on what constitutes acceptable/unacceptable interruptions in each zone is different:

Zone 1

start of requiredreading time

Zone 3

Direction of travel

4 seconds

greater of 40mor 1 second (seesection B5.2.4)

closest normal stopping

positionto signal

Zone 2

Figure 3.2

3.2.1 Zone 1 Section 5.2.4 of this standard prohibits any interruption of the driver’s view of the signal in this zone.



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3.2.2 Zone 2 Consideration should always been given to the complete removal of the sources of interruption, however, partial interruptions of the driver’s view of the signal may be acceptable in this zone if they conform to all the following limitations:

a) The obstruction by any item of infrastructure results in less than approximately one third of any element of the signal being obscured at any one time.

b) The obstruction lasts for less than half a second when viewed at the permissible speed.

c) No more than two such interruptions of a signal should occur in this zone, and they should be separated by an interval of at least one second when viewed at the permissible speed.

3.2.3 Zone 3 Interruptions to the driver’s view of the signal of the types listed below may be acceptable in this zone:

a) A single full or partial interruption of up to one second when viewed at the permissible speed.

b) Up to two full or partial interruptions that do not exceed two thirds of a second each, separated by an interval of at least half a second, and cumulatively not exceeding one second when viewed at the permissible speed.

c) Up to four full or partial interruptions that do not exceed one third of a second each, each one separated by an interval of at least half a second, and cumulatively not exceeding one second when viewed at the permissible speed.

3.2.4 Requirements common to zones 2 and 3

In zones 2 and 3, it is important that the following requirements are also met:

a) Any remaining visible element(s) could not be misread as a less restrictive aspect, and

b) The required reading time available is greater than the minimum reading time by an amount equal to or greater than the interruption time (see section 5.2.2 for the definition of minimum reading time).

3.3 Trains on adjacent lines Trains passing on adjacent lines are not normally regarded as obstructions to the viewing of signals, but trains on adjacent lines where they are likely to come to a stand should be regarded as obstructions. This should be understood to include trains carrying out station stops, trains or vehicles standing in loop lines or sidings, and trains standing at signals where the stop aspect is regularly encountered.



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References

Railway Group Standards

GA/RT6001 Railway Group Standards Change Procedures

GA/RT6004 Temporary Non-Compliance with Railway Group Standards

GA/RT6006 Derogations from Railway Group Standards

GE/RT8025 Electrical Protective Provisions for Electrified Lines

GE/RT8029 Management of Clearances and Gauging

GE/RT8034 Maintenance of Signal Visibility (in draft at the time of publication of this document)

GE/RT8035 Automatic Warning System (AWS)

GE/RT8048 Signal Post Telephones (in draft at the time of publication of this document)

GI/RT7001 Management of Safety Related Records of Elements of the Infrastructure

GI/RT7006 Prevention and Mitigation of Overruns – Risk Assessment

GK/RT0031 Lineside Signals and Indicators

GK/RT0032 Lineside Signal Aspect Sequences (to be retitled ‘Provision of lineside signals’, incorporating material from GK/RT0035)

GK/RT0033 Lineside Signs

GK/RT0034 Lineside Signal Spacing

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

GK/RT0207 Signalling Design

GK/RT0209 Testing and Commissioning of Signalling and Operational Telecommunications Systems

GM/RT2149 Requirements for Defining and Maintaining the Size of Railway Vehicles

GM/RT2161 Requirements for Driving Cabs of Railway Vehicles

GO/RT3252 Signals passed at Danger (SPADs)

GO/RT3255 Train Working – Competence and Fitness

Other References British Meteorological Office Observer’s Handbook

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.


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