Lineside Signals and Indicators - RSSB Iss 4.pdf · This document defines the format, presentation and constraints on usage of lineside equipment to be used for the signalling 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/RT0031 Issue Four Date February 2002

Lineside Signals and Indicators

Synopsis This document defines the format, presentation and constraints on usage of lineside equipment to be used for the signalling of trains.

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Document to be Withdrawn as of 03/04/2010 To be Superseded by GKRT0045 Iss 1 Published on 06/02/2010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/RT0031 Issue Four Date February 2002 Page 1 of 35

Contents Section Description Page

Part A

A1 Issue record 2 A2 Implementation of this document 2 A3 Scope of Railway Group Standards 3 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 5 B4 Colour light signal 6 B5 Colour light splitting distant signal 8 B6 Co-acting signal 10 B7 Banner repeating signal 10 B8 Position light signal 12 B9 Position light junction indicator 13 B10 Alphanumeric route indicator 15 B11 Points indicator 16 B12 Driver’s level crossing indicator 17 B13 Loading / unloading indicator 17 B14 SPAD indicator 18 B15 Signal OFF indicator 19 B16 Right away indicator 20 B17 Close doors indicator 20 B18 Barriers up indicator 20 B19 Stop board 21 B20 Distant board 22 B21 Semaphore stop signal 22 B22 Semaphore distant signal 24 B23 Semaphore subsidiary signal 25 B24 Semaphore shunting signal 26 B25 Buffer stops on signalled routes 27 B26 Colour requirements 28 B27 Equipment performance requirements 29 B28 Permitted associations of aspects and indicators 32

References 34




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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

January 1996 Initial issue. Replaced SSP2, GS/ST0003, SSP4, SSP6 (sections 5 and 8 only), GS/ST0008, SSP13, SSP15, SSP29, SSP44, SSP45, SSP60, SSP63, SSP67, SSP82 and JDP C001.

Two December 1996 Replaced GK/RT0031 issue one.

Three October 1999 Replaced GK/RT0031 issue two, and section 8 of GK/RT0005 issue one which had been revised and incorporated into this document as sections 4.1 – 4.3 inclusive.

Four February 2002 Replaces GK/RT0031 issue three. Replaces CP-PM-040, parts of which have already been incorporated into GC/RT5033

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 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 by GK/RT0031 issue 4

Date(s) as of which sections are superseded

GK/RT0031 3 Lineside Signals and Indicators

All 6 April 2002

(GK/RT0031 issue 3 withdrawn as of this date)

GK/RT0035 2 Layout of Lineside Signals

7, 15 6 April 2002

(GK/RT0035 issue 2 withdrawn as of this date)

CP-PM-040 1 Provision of Buffer and Wheel Stop Lighting

4.2, 4.3

6 April 2002 (CP-PM-040 withdrawn as of this date) All other sections of CP-PM-040 have been superseded by




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GC/RT5033 already.

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 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

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 format, presentation and constraints on usage of lineside equipment to be used for the signalling of trains.

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 This document does not include requirements for maintenance of signal visibility, aspect sequences, signal spacing or positioning (see GE/RT8034, GK/RT0032, GK/RT0034 and GK/RT0037 respectively).

B3 Definitions Centre-line (of signal or indicator) The line (usually extending out perpendicularly from the face of a signal) forming the optical axis of the beam.

Chromaticity (for lights only) The co-ordinates of a colour which may be plotted on the 1931 CIE (Commission Internationale de l’Eclairage) Chromaticity diagram to graphically represent the colour.

Straight-ahead route The non-diverging (and usually the fastest) route from a junction signal.

Signal red, signal yellow, signal green, signal white, lunar white Throughout this document these light colour descriptions correspond to the appropriate colour definition in section B26.1 of this document. The prefix ‘signal’ is omitted from text references other than in respect of white.




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Splitting distant A colour light splitting distant signal consists of two colour light signal heads side by side. The two heads are referred to as the ’main’ and ‘offset’ heads (see section B5 for further details).

For the purpose of this document the term splitting distant signal, without further qualification, applies to both inner and outer splitting distant signals. Any reference to an inner splitting distant signal applies equally to the only splitting distant signal where an outer splitting distant signal is not provided. Outside the context of this document, however, the prefix ‘inner’ need not be used when referring to a splitting distant signal at locations where there is no outer splitting distant.

Red, Yellow, Green, White, Blue, Grey Throughout this document the surface colour descriptions correspond to the appropriate colour definition in sections B26.2 and B26.3 of this document.

Silver For the purposes of this document only, a galvanised or grey finish can be regarded as meeting a requirement for a silver surface colour.

Other defined terms are included in GK/RT0002 and GK/RT0037.

B4 Colour light signal B4.1 Description B4.1.1 General A colour light signal is a signal used for controlling running movements. It shall display its aspects only by means of red, yellow and green coloured lights for main class routes.

Each signal shall display only one of the aspects defined in Table 1 at a time. No other combination of lights shall be displayed. This restriction on the combinations of signal aspects displayed simultaneously does not apply to colour light splitting distant signals or co-acting signals (special requirements apply to these types of signal and they are dealt with in sections B5 and B6 respectively).

An aspect shall be displayed at all times.

B4.1.2 Disposition of aspects Where a double yellow ‘preliminary caution’ aspect is required the nominal vertical separation of the yellow lights shall be 510 mm (tolerance +20 mm/- 10 mm), centre to centre, subject to the readability requirement being met.

Where an optical arrangement is employed that enables red, yellow and green aspects to be displayed through the same lens, the vertical separation between the two lights of the double yellow aspect shall be maintained. Otherwise, the arrangement of optical units shown in Figure 4.1.2 shall be adopted. It is permissible for the optical units of a signal that does not exhibit a double yellow aspect to be mounted horizontally, provided that the order of proximity to the driver’s line of sight is maintained (see GK/RT0037).




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200 MIN DIASIGNAL LIGHTAPERTURES

FRONT COLOURBLACK

300 min 300 min

300

min

255

10 510 5

10 525

525

518

0 m

in

All dimensions are in millimetres

Figure 4.1.2 Four aspect colour light signal

Aspect Description Meaning to Driver Red light Danger Stop.

One yellow light

Caution Proceed: Be prepared to stop at the next signal.

Two yellow lights displayed vertically

Preliminary caution Proceed: Be prepared to find the next signal exhibiting one yellow light.

One flashing yellow light

Preliminary caution for a diverging route

Proceed: Be prepared to find the next signal exhibiting one yellow light with junction indication for diverging route(s).

Two flashing yellow lights displayed vertically

Indication of diverging route ahead of next but one signal

Proceed: Be prepared to find the next signal exhibiting one flashing yellow light.

Green light Clear Proceed: The next signal is exhibiting a proceed aspect.

Table 1

B4.2 Application The application requirements for colour light signals are set out in GK/RT0032 and GK/RT0037.




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B5 Colour light splitting distant signal

B5.1 Description A colour light splitting distant signal consists of two colour light signal heads side by side. The two heads are referred to as the ‘main’ and ‘offset’ heads.

B5.1.1 Main head The main head conveys information about the route from the splitting distant signal to the junction signal ahead. When a splitting distant also acts as a stop signal, the main head shall carry the red aspect.

For signals positioned on the left of the line, the main head applies to the straight-ahead route for signals approaching a left hand divergence, and to the diverging route for signals approaching a right hand divergence (see figures 5.1.5a and 5.1.5b, and GK/RT0032).

B5.1.2 Offset head For signals positioned on the left of the line, the offset head shall be positioned to the left of the main head and:

a) for a left-hand divergence, apply to the diverging route and be positioned lower than the main head

b) for a right-hand divergence, apply to the straight-ahead route and be positioned higher than the main head.

When a splitting distant signal is located other than on the left of the line, equivalent arrangements shall apply to ensure that the main head is located as near as possible to the driver’s line of sight.

The offset head shall be lit only when a route is set beyond the junction signal. Where a splitting distant is itself a junction signal, the appropriate route indication for that junction shall be displayed in association with the main head only.

B5.1.3 Restriction on use as flashing yellows An inner splitting distant signal shall not be capable of displaying a flashing single yellow aspect, nor an outer splitting distant of displaying a double flashing yellow aspect.

B5.1.4 Permissible combinations Permissible combinations of aspects for signals positioned on the left of the line are shown in GK/RT0032 Appendix 4.

Where three aspect signalling is in use, the preliminary caution aspects are omitted.

An isolated splitting distant displays only caution and clear aspects. This shall also apply if the isolated colour light splitting distant signal applies in absolute block signalling reading up to a semaphore junction signal.

Lights which are shown as being horizontally level in figures 5.1.5a and 5.1.5b shall be displayed such that they appear level to an extent sufficient to satisfy the Signal Sighting Committee (see GK/RT0037).

B5.1.5 Horizontal separation The horizontal separation between the aspect centres on adjacent heads of a colour light splitting distant shall be a nominal 900 mm. Where this separation cannot be achieved, it is permissible for the horizontal separation to be reduced, but not to less than 600 mm.




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600mm or 900mm


Y

G R

Y

Y

Y

G

Figure 5.1.5a Colour light splitting distant head (left-hand divergence)

600mm or 900mm


G

Y

Y Y

G

R

Y

Figure 5.1.5b Colour light splitting distant head (right-hand divergence)




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B5.2 Application The circumstances in which splitting distant signals are used to control the approach to junction signals and the aspect sequences that apply are set out in GK/RT0032.

B6 Co-acting signal B6.1 Description A co-acting signal repeats the aspects of a main signal. All signals or indicators used in a co-acting application shall meet the standard performance requirements for that primary signal or indicator unless agreed otherwise by the Signal Sighting Committee. It is permissible for co-acting signals to be provided for colour light or semaphore main signals.

B6.2 Application The co-acting signal shall be controlled to the same main aspect as the primary signal. Main routes up to the signal shall require both signals proved lit at the correct aspect.

The infrastructure controller shall assess the risks of non-provision of position light or subsidiary aspects (and associated route indicators) on the co-acting signal. These aspects and the risk assessment indicates that they are necessary:

a) for operational reasons, or

b) to avoid misleading drivers.

Further application requirements for co-acting signals are set out in GK/RT0037.

B7 Banner repeating signal B7.1 Description A banner repeating signal indicates whether the signal ahead is ON or OFF.

Banner repeating signals shall consist of a rectangular unlit, or black, bar displayed against a white background. The dimensions of a banner to category 2 shall be as shown in Figure 7.1 where the white light is directly transmitted (eg fibre optic devices). Where the white light is reflected or used to silhouette a banner arm, it is permissible for the proportion of white area to be greater, provided the signal meets the readability requirement of section B27.2.

200

+0 -12

150

+6 -015

0+6 -0

1. In accordance with BR1651 Part 3Box is as for SARI: 600mm x 600mmDisc is 500mm Dia.2. All dimensions in millimetres.

WHITE

WHITE

BLACK ORUNLIT

Figure 7.1 Banner repeating aspect




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Where category 3 banner repeating signals are provided on station platforms (see section B7.2.2), the proportions of black and white shall be the same as for a category 2 banner.

The permissible aspects shall be as shown in Table 2.

Aspect Description Meaning to Driver Horizontal arm ON Be prepared to find the related signal

at danger

Arm at an upper quadrant angle of 45°

OFF Related signal is exhibiting a proceed aspect

Table 2

B7.2 Application B7.2.1 Criteria for use It is permissible to provide banner repeating signals in the following circumstances:

a) where a signal is frequently approached at danger and, in order to reduce delay, it is desirable to advise the driver that the signal has cleared before the driver can see the main aspects

b) where there have been particular difficulties in drivers misjudging or disregarding the main signal which have resulted in repeated incidents of the signal being passed at danger

c) where local conditions are such that it is reasonable to predict that the problems with drivers misjudging or disregarding the main signal are likely to occur. GK/RT0037 also permits the provision of a banner repeater in certain circumstances where the required reading time for a main signal aspect cannot be achieved.

B7.2.2 Use on station platforms Banner repeating signals meeting performance category 2 shall be used except in respect of station platforms, where it is permissible to use a category 3 banner, so long as the sighting requirements can still be met (see section B27 for equipment performance requirements and GK/RT0037).

B7.2.3 Splitting banner signals It is permissible for two banner signal heads to be combined to form a splitting banner repeating signal. Splitting banner signals with more than two banners are not permitted. Centre to centre distance between the two banners of a splitting banner repeating signal shall be 1000 mm in the horizontal and 500 mm in the vertical (+/- 10%).

Splitting banner repeating signals shall only be used where:

a) a banner repeating signal is required on the approach to a junction signal

b) it is necessary to distinguish between an OFF banner aspect for the straight-ahead route and an OFF banner aspect for any other route.

A splitting banner signal head shall only clear when the related signal is cleared for the route(s) to which it refers; it shall remain in the ON position at all other times. The higher splitting banner head shall refer to the straight-ahead route, which shall always be the fastest route (otherwise a splitting banner signal is not permitted); the lower splitting banner head shall refer to a diverging route (or routes). The relative horizontal positions of the two splitting banner signal heads shall indicate the direction of the divergence (to the left or right) relative to the straight-ahead route.




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The splitting banner head for the straight-ahead route shall not clear for any other route. It is permissible for the splitting banner head for a diverging route to clear for more than one diverging route, provided all routes to which it refers have the same permissible speed, diverge from the straight-ahead route through the same set of points, and do not differ in any other characteristic which could have a bearing on safety or operational efficiency (such as provision of electrification).

B7.2.4 Single banner at junction If a banner applies to more than one route, the junction signal shall be equipped with facilities for temporary approach control from red, effective until the train has reached a position from which the driver is able to read the junction indication on the main signal. This is for use with temporary speed restrictions ahead of the junction signal (see GK/RT0032).

B8 Position light signal B8.1 Description A position light signal (PLS) shall display its aspects by means of the position and colour of lights. Each signal shall display only one of the aspects defined in Table 3 at a time.

Aspect Description Meaning to Driver

Two red lights horizontally displayed

ON (Red) Stop.

One red light to the left of one lunar white light, horizontally displayed (see section B8.2.1)

ON (Red) Stop.

Two yellow lights horizontally displayed (see section B8.2.2)

ON (Yellow) Stop.

(Applies only to movements travelling in the direction(s) to which the signal can be cleared. Other movements may pass the signal without it being cleared.)

No aspect (where associated with a main aspect)

ON (No light) Obey main aspect.

Two lunar white lights displayed at an upper quadrant angle of 45

OFF The line ahead may be occupied. Proceed cautiously towards the next stop signal, stop board or buffer stops. Be prepared to stop short of any obstruction. The associated main aspect (where provided) may be passed at danger.

Table 3




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B8.2 Application B8.2.1 Use of PLS with two red lights Independent PLSs which display a red/red ON aspect shall be used for all new installations.

Consideration shall be given to the conversion of red/white PLSs to the type with a red/red ON aspect in respect of existing installations. All signals in a given locality shall be converted at the same time.

B8.2.2 Use of PLS with two yellow lights Independent PLSs which display a yellow/yellow ON aspect shall be used to replace yellow/white PLSs only as part of a programme for conversion of red/white PLSs with signals having a red/red ON aspect. Otherwise, the use of yellow/yellow PLSs is not permitted.

B8.2.3 Use as limit of shunt signal Where the purpose of the position light signal is to mark the end point of a shunting movement in the opposite direction to the usual flow of traffic (limit of shunt), the only permitted configuration of the signal is that which displays two red lights permanently illuminated. In this case it shall be proved lit.

B9 Position light junction indicator

B9.1 Description B9.1.1 Orientation A position light junction indicator indicates the route to be taken by the angle at which a line of lunar white light points is displayed. Permitted positions are shown in Figure 9.1.1.

52

41

3 6

700

Max

.55

0 M

in

Frontcolour black


764 Max. 710 Min

between centreline

of lenses176Min

Figure 9.1.1 Junction indications

The indicators shall be positioned at 45°, 90° and 135° to the vertical and shall be positioned above the main aspect, except where permitted by GK/RT0037.




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Indication Meaning to Driver No indication, signal ON Obey main aspect

No indication, signal OFF Obey main aspect, straight-ahead route is set

Position 1 indication, signal OFF Obey main aspect, expect divergence to left

Position 2 indication, signal OFF Obey main aspect, expect divergence to left more extreme than that for position 1 indication

Position 3 indication, signal OFF Obey main aspect, expect divergence to left more extreme than that for position 2 indication

Position 4 indication, signal OFF Obey main aspect, expect divergence to right

Position 5 indication, signal OFF Obey main aspect, expect divergence to right more extreme than that for position 4 indication

Position 6 indication, signal OFF Obey main aspect, expect divergence to right more extreme than that for position 5 indication

Table 4

B9.1.2 Restrictions on use Position light junction indicators in diametrically opposing positions (1 and 6, 2 and 5, 3 and 4) shall be avoided where there is the potential for confusion. In such cases, consideration shall be given to the use of alternative methods of route indication. Diametrically opposing route indications can be particularly ambiguous where:

a) a signal has a curved approach

b) the main head is stepped forward from the position light junction indicator.

B9.1.3 Successive junctions Where successive signals apply to diverging routes in the same direction and are equipped with position light junction indicators, the possibility of a driver becoming misled into taking the first junction indicator as applying to the junction beyond the second signal shall be taken into account. In such circumstances, the use of standard alphanumeric route indicators shall be considered.

B9.2 Application B9.2.1 Meaning Position light junction indicators shall usually be used in association with colour light signals for simple divergences to the left or right.

No indication shall be given for the straight-ahead route (usually the highest speed route) except that, where there is no geographically obvious straight-ahead route, a junction indicator shall be provided for all signalled routes.

It is permissible for signals to be equipped to display multiple indicators, according to the final destination relative to the main or straight-ahead route in the manner shown in Figure 9.2.1, commencing on each side at positions 1 and 4 as shown in Table 4.

Only one indication shall be displayed at a time.




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NO INDICATIONPOSITION 4POSITION 5POSITION 6

POSITION 3POSITION 2POSITION 1NO INDICATION

Figure 9.2.1 Examples of junction indications

B9.2.2 Controls A position light junction indicator shall display an indication only when the controls for the associated signal permit the latter to display a proceed aspect.

Position light junction indicators shall be proved sufficiently lit to be visible before the associated stop signal is permitted to clear for a diverging route.

B10 Alphanumeric route indicator

B10.1 Description B10.1.1 Permissible ciphers An alphanumeric route indicator indicates the route to be taken using numbers or letters (or a combination of numbers and letters). The display shall be illuminated and the colour of light shall be signal white.

The character font shall approximate to Gill Sans light. Only the following characters shall be used.

A B C D E F G H K L M N P R S T U W X Y Z 1 2 3 4 5 6 7 8 9 0

In addition it is permissible for the letters ‘O’ and ‘V’ to be used only as part of an alphabetic indication where the letter has a clear geographic meaning (for example ‘UO’ for Up Oldham, to differentiate from ‘UR’ for Up Rochdale).

Where more than one character is used in an indication, the minimum distance between the outermost points on adjacent characters shall be 20% of character height.

B10.1.2 Standard and miniature alphanumeric route indicators Alphanumeric route indicators meeting performance category 2 are termed standard alphanumeric route indicators, and those that only meet performance category 3 are termed miniature alphanumeric route indicators (see section B27 for performance requirements). An indication meeting category 2 readability criteria shall not be used with a category 3 signal.

The terms ‘Standard’ and ‘Miniature’ are not specific to the size of the indicator housing. They refer to the readability of the indications.

B10.2 Application Alphanumeric route indicators shall be positioned as required by GK/RT0037.

The indications used shall appear logical to the driver as a description of the route ahead.




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The same characters shall be used at all signals which are equipped to show an indication for a given destination. The use of the same characters on signals in any one locality, for different destinations in the same direction, is not permitted.

An indication shall only be displayed when the controls for the associated signal permit the latter to display a proceed aspect.

B10.2.1 Alphanumeric route indicators associated with main aspects When a standard alphanumeric route indicator is provided for a main signal an indication shall be displayed for each route from the signal except that, where the permitted speed for the straight-ahead route is more than 10 mph above that for any other, no indication need be provided for that route. The indicator shall be proved lit before the signal is permitted to show a proceed aspect.

Where there is a risk arising from a driver misinterpreting the route set due to corruption of the display (eg the figure ‘8’ being changed to a ‘9’, ‘6’ or ‘0’), this proving shall prevent the signal from displaying a proceed aspect in the event of such corruption.

Where a standard alphanumeric route indicator is provided on the approach to a terminal or other large station, an indication shall be provided for all routes.

B10.2.2 Alphanumeric route Indicators associated with position light signals The only form of route indication which it is permissible to provide with a position light aspect is an indication meeting no better than category 3 performance requirements.

An indication shall be provided for all routes from an independent position light signal in situations where:

a) one or more routes has its exit at a limit of shunt or a signal which if passed at danger could cause a serious hazard

b) there is a significant difference in the nature of the routes (eg in terms of distance to next signal)

c) a 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).

An indication shall be provided for each route from a subsidiary position light signal, except where there is only one route to which the signal applies.

For both independent and subsidiary signals, if the routes are very similar in nature, eg to a fan of sidings of the same length, it is permissible to provide the same route indication (eg ‘SDG’).

B11 Points indicator B11.1 Description A points indicator informs the driver whether facing points are correctly closed (See GI/RT7004). The indications shall be as shown in Table 5.

Indication Meaning to Driver

Red light (No light – obsolescent – see section B11.2)

Stop; do not pass over points until they have been secured.

Yellow light Points are correctly set.

Table 5




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B11.2 Application A points indicator shall be used on the approach to all train operated facing points, except where a signal is provided.

It is also permissible for a points indicator to be used to indicate that power operated points are correctly locked and detected on lines which do not have conventional lineside signals (eg RETB fitted routes).

It is permissible for the format of indicator which uses only a yellow light to be fitted for consistency on lines of route which use this obsolescent form.

B12 Driver’s level crossing indicator

B12.1 Description A driver’s level crossing indicator informs the driver of the correct operation, or otherwise, of a locally monitored automatic level crossing. The permitted indications are shown in Table 6.

Indication Meaning to Driver Red flashing light Stop; crossing has not operated correctly. Signal White flashing light Proceed if crossing clear; crossing has

operated correctly.

Table 6

B12.2 Application Application requirements are defined in GI/RT7012 (Design, Construction and Maintenance of Level Crossings).

B13 Loading / unloading indicator

B13.1 Description Loading / unloading indicators convey instructions to the driver by means of the position and colour of lights and are used to control trains in sidings. They do not give authority for a train to proceed past other lineside signals or out of sidings. The indications which are permissible and associated meanings are as shown in Figure 13.1.

MOVE SLOWLY IN THENORMAL DIRECTION FORLOADING OR UNLOADING

STOP IMMEDIATELY,IRRESPECTIVE OFDISTANCE FROMTHE INDICATOR

PREPARE TO STOP

MOVE SLOWLY IN THEOPPOSITE DIRECTION TO

THAT REQUIRED FORLOADING OR UNLOADING

FLASHINGLIGHTS

NOTE:

SIGNALWHITE LIGHT

SIGNALRED LIGHT

Figure 13.1 Loading / unloading indicators




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These indications shall not override any other signal, handsignal or indication that requires the driver to stop.

Each indicator shall display no more than one of the indications shown in Figure 13.1 at any one time. It is permissible for indicators to be grouped in sets referring to a given line. All indicators in a set shall display the same indication at any one time. Indications shown as angled shall be at 45° to the horizontal.

All readable indications in a set shall be considered valid by the driver regardless of their position relative to the train. If the indicators go out while a train is under their control the train is required to stop immediately. It is permissible for the complete set of indicators at a given location to be extinguished when not in use.

B13.2 Application Loading / unloading indicators shall only be used as an aid to the movement and positioning of trains; they are not intended to help prevent collision or derailment of trains, and they shall usually be controlled from the position at which the loading / unloading operation is supervised, rather than from a signalbox, ground frame or shunting frame.

A signal capable of displaying a stop aspect shall protect the running lines beyond the siding. If this signal has a route towards a headshunt which is used for loading / unloading, the signal being ‘ON’ shall inhibit any indicators along the headshunt from illuminating.

Any loading / unloading indicators which direct movements into a signalled area shall only be illuminated when the relevant signals are displaying a proceed aspect.

Indicators shall be elevated, where practicable, and shall be located at intervals along the track such that the driver has a clear view of at least one indicator at all times under clear visibility conditions.

B14 SPAD indicator B14.1 Description A SPAD indicator (Figure 14.1) shall display a steady red light between flashing red lights, when the signal to which it applies is passed without authority.

The meaning to drivers is: ‘Stop immediately - do not proceed except on the authority of the signaller’.

The indicator shall not be illuminated under normal operating circumstances.

The indicator shall be mounted against a backplate, or within a surround, the front of which shall be coloured blue (see section B27.2).




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200 MIN DIASIGNAL LIGHTAPERTURES

FRONTCOLOUR BLUE

300 min 300 min

300

min

10 510 5

255

255

180

min


Figure 14.1 SPAD indicator

B14.2 Application It is permissible to provide SPAD indicators as a risk mitigation measure (see GI/GN7606 Guidance Note: Prevention and Mitigation of Overruns – Risk Assessment).

The position of the indicator shall be selected to maximise the likelihood of an unauthorised movement being brought to a stand before reaching any area of conflict and, 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 (see GK/RT0037).

In positioning a SPAD indicator, it is necessary to balance the following requirements:

a) to maximise the length of time for which drivers have the opportunity to see the SPAD indication after a SPAD has occurred

b) to ensure the perceived intensity of the indication is at a high level as soon as possible after the signal is passed.

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

B15 Signal OFF indicator B15.1 Description Signal OFF indicators are provided to assist train despatch staff. An OFF indicator shall display the illuminated word ‘OFF’. It is permissible for it to be double-sided. The indication shall be signal white and the character font shall approximate to Gill Sans light.

B15.2 Application An OFF indicator shall display ‘OFF’ only when the signal(s) to which it applies is displaying a proceed aspect. No indication shall be shown when the signal is at danger.




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On platform lines with mid-platform signals, an OFF indication for routes from the mid-platform signal shall usually be displayed only when the signal at the platform end is also off. It is permissible not to apply this requirement if operating practices require a train to proceed along the platform, provided the indicators are marked to show precisely to which signal they apply.

In the circumstances defined in section B7.2.2, it is permissible for an OFF indicator also to perform the function of a banner repeating signal.

For further application details, see GK/RT0037.

B16 Right away indicator B16.1 Description A right away indicator shall display the illuminated letters ‘RA’. The indication shall be signal white and the character font shall approximate to Gill Sans light. The meaning to drivers is that station duties are complete and it is safe to proceed in accordance with the signal aspect (where provided).

B16.2 Application Right away indicators shall be used where a ‘ready to start’ hand signal is necessary for some or all of the trains using a platform, but the driver may be unable to see the hand signal. A secure operating device shall be provided for use by platform staff. No indication shall be displayed unless any associated signal is showing a proceed aspect.

It is also permissible for right away indicators to be used as a SPAD reduction measure in circumstances described in GI/RT7006 and GI/GN7606.


B17 Close doors indicator B17.1 Description A close doors indicator shall display the illuminated letters ‘CD’ when operated by platform staff. The indication shall be signal white and the character font shall approximate to Gill Sans light. The meaning to drivers is that it is safe for the power operated doors on the train to be closed.

B17.2 Application

It is permissible for close doors indicators to be provided at stations with platform staff where driver only trains operate, as an alternative to the provision of CCTV monitoring equipment or mirrors. An operating device shall be provided for use by platform staff. Application requirements are defined in GO/RT3205 (Close Doors Indicators at Platforms). Where CD and RA indicators are combined into a common unit and both indications are displayed in the same field, then the RA indication shall supersede the CD indication.


B18 Barriers up indicator 18.1 Description A barriers up indicator shall display the illuminated letters ‘BU’ when the associated barriers are fully raised. The indication shall be signal white and the character font shall approximate to Gill Sans light. The meaning to train crew is that the operation of raising the barriers at the crossing that the train has just traversed has been successful.

B18.2 Application It is permissible to provide a barriers up indicator at trainman operated crossings with barriers. The indicator shall be positioned at a distance beyond the crossing approximately equal to the length of the longest train which is expected to use the




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crossing plus an allowance for sighting and the distance covered by the train while the barriers are rising (see GI/RT7012).

B19 Stop board B19.1 Description A stop board shall display a fixed danger aspect and written instructions regarding the action to be taken after stopping. The colours and permitted dimensions are shown in Figure 19.1. Reflectivity performance shall be no worse than that associated with Class 1 retro–reflective material (as defined in BS 873 Part 6).

Notes:

1. RED

BLACK

WHITE

2. Colour of backof sign (includingstiffening): grey.

3. Dimensionsmay vary 5%.

4. Wording on lowerpart of sign mayvary as required forspecific application.

Stop Whistle before proceedingm m

b

n

l

n

i

a

c c c

d

e

f

g

h

jk

k

c

Figure 19.1 Stop board

a b C D e f g h i j k l m n

Large Board

1650 900 10 120 500 120 180 150 20 540(min)

65 65 130(min)

130

Medium Board

1300 700 10 100 400 100 140 120 20 400(min)

50 50 100(min)

100

Small Board

700 400 5 55 220 50 80 65 10 210(min)

30 30 60 (min)

60 (min)

All dimensions in mm

Table 7

The font for wording on the sign shall be the same as for road signs as specified in Schedule 13 Part II of Statutory Instrument No. 1519 of 1994: The Traffic Signs Regulations and General Directions 1994.

The meaning to drivers is as follows: ‘Stop - do not proceed except in accordance with the instructions exhibited or on the authority of the authorised person’.

B19.2 Application The application requirements for stop boards are set out in GK/RT0037.




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B20 Distant board B20.1 Description A distant board shall display a fixed caution aspect. Its colours and dimensions shall be as shown in Figure 20.1. Reflectivity performance shall be no worse than that associated with Class 1 retro–reflective material (as defined in BS 873 Part 6).

85 mm

YELLOW

WHITE

BLACK

Notes:

1. Colour of back of sign (includingstiffening) : grey

900 mm

900

mm

200

mm

80 m

m80

mm

205 mm

170 mm

2. Tolerance on dimensions: ± 5%

Figure 20.1 Distant board

The meaning to the driver is to be prepared to stop at the home signal or other specified place to which the distant board applies.

B20.2 Application It is permissible for retro-reflective distant boards to be used on the approach to a colour light stop signal, semaphore stop signal, stop board, points indicator or buffer stop at the end of a line, as an alternative to a fixed distant signal, under the conditions permitted by GK/RT0032.

B21 Semaphore stop

signal B21.1 Description A semaphore stop signal is a running signal which displays its aspects by means of a rectangular semaphore arm by day and coloured lights by night.




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The arm shall be coloured red with a vertical white stripe; the dimensions of an arm meeting performance category 4 (see section B27) shall be as shown in Figure 10, although minor variations to these dimensions are permitted where consistency of appearance with other signals in the same locality is required, provided that the performance requirements of section B27.1 are still met.

SIGNALPOSTEND

SIGNALPOSTEND

BACK VIEW

FRONT VIEW

RED

BLACK

WHITE

178 mm 318 mm

178 mm318 mm

1060 mm

260

mm

Tolerance on all dimensions: ± 5%

Figure 21.1 Semaphore stop signal

Only the aspects shown in Table 8 shall be displayed.


Arm horizontal (visible by day) with red light displayed (visible by night)

Danger Stop

Arm raised or lowered by angle of 45° (visible by day) with green light displayed (visible by night)

Clear Proceed

Table 8

In this section and in sections B22, B23 and B24, the tolerances on angular displacements for mechanical signals shall be:

• -5° to 5° from horizontal for ‘ON’ position • 35° to 65° from horizontal for ‘OFF’ position

B21.2 Application The application requirements for semaphore stop signals are set out in GK/RT0032 and GK/RT0037.




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B22 Semaphore distant signal

B22.1 Description B22.1.1 General A semaphore distant signal is a running signal which shall display its aspects by means of a semaphore arm by day and coloured lights by night.

The arm shall have a fishtail end and shall be coloured yellow with a black chevron; its dimensions shall be as shown in Figure 22.1.1, although minor variations to these dimensions are permitted where consistency of appearance with other signals in the same locality is required, provided that the performance requirements of section B27.1 are still met.

SIGNALPOSTEND

SIGNALPOSTEND

BACK VIEW

FRONT VIEW

YELLOW

BLACK

WHITE

210 mm 241 mm

190 mm

210 mm241 mm

1060 mm

102 mm

25 mm

25 mm

260

mm


Figure 22.1.1 Semaphore distant signal

Only the aspects shown in Table 9 shall be displayed (see section B21.1 for tolerances on angular displacement).

Aspect Description Meaning to Driver Arm horizontal (visible by day) with yellow light displayed (visible by night)

Caution Be prepared to stop at the home signal or other specified place to which the distant signal applies


Clear All associated stop signals are clear

Table 9




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B22.1.2 Semaphore splitting distants It is permissible for semaphore distant signal arms to be combined on a single signal to form a semaphore splitting distant signal. In such cases, each signal arm shall apply to a different route from the junction signal for which the signal acts as the splitting distant.

B22.2 Application The application requirements for distant signals are set out in GK/RT0032 and GK/RT0037. It is permissible for a distant signal arm to be combined with a semaphore stop signal arm, but the distant arm shall display a clear aspect only when the associated stop arm is also in the clear position.

B23 Semaphore subsidiary signal

B23.1 Description A semaphore subsidiary (eg warning or calling-on) signal shall display its aspects by means of a rectangular semaphore arm by day and coloured lights by night. The arm shall be coloured white with two horizontal red stripes; its proportions shall be as shown in Figure 23.1 although minor variations to these dimensions are permitted where consistency of appearance with other signals in the same locality is required, provided that the performance requirements of section B27.1 are still met.

RED

BLACK

WHITESIGNAL

POST END

BACK VIEW

FRONT VIEW

115mm 152mm

SIGNALPOSTEND

533mm

159m

m

41mm

77mm


Figure 23.1 Semaphore subsidiary signal


Aspect Description Meaning to Driver Arm horizontal (visible by day) with white light displayed (visible by night)

Normal Obey main signal


Proceed The main signal may be passed at Danger. The line ahead may be occupied. Proceed cautiously being prepared to stop short of any obstruction.

Table 10




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B23.2 Application The application requirements for semaphore subsidiary signals are set out in GK/RT0037.

B24 Semaphore shunting signal

B24.1 Description A semaphore shunting signal shall display its aspects by means of either a miniature rectangular semaphore arm or a semaphore disc by day; and by coloured lights (or floodlighting of the disc) by night. (see Figure 24.1).

RED

BLACK

WHITESIGNAL

POST END

BACK VIEWARM TYPE

115mm 152mm

FRONT VIEWARM TYPE

SIGNALPOSTEND

115mm152mm

533mm

159m

m

146mm

102mm

BACK VIEWDISC TYPE

FRONT VIEWDISC TYPE


146mm

Figure 24.1 Shunting signal

The illustrated back view of the disc type signals is not always visible to train crew and signallers, dependent on the method of mounting the disc signal on the signal mechanism.



Disc with red bar horizontal or red and white horizontal arm (visible by day) with red light displayed (visible by night)

Normal Stop

Disc turned 45° or arm raised or lowered by angle of 45° (visible by day) with green light displayed (visible by night)

Proceed Proceed as far as the line is clear

Table 11




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B24.2 Application The preferred form of semaphore signal for new works in mechanically signalled areas is the disc form of shunting signal.

B25 Buffer stops on signalled routes

B25.1 Description B25.1.1 Requirement

The presence of a buffer stop on a signalled route shall be indicated to the driver by means of a retro-reflective surface on the buffer stop. In addition, buffer stop lights shall be provided, except as allowed by section B25.2.

Other requirements for the design of buffer stops are set out in GC/RT5033.

B25.1.2 Retro-reflective strip The usual arrangement of colours for retro-reflective surfaces on a typical buffer stop is shown in Figure 25.1.2. Where the design of buffer stop does not permit this form to be complied with precisely, the principle of providing at least one horizontal white strip bounded by red strips above and below shall be followed, and the approval of a Signal Sighting Committee shall be obtained. Reflectivity performance shall be no worse than that associated with Class 1 retro–reflective material (as defined in BS 873 Part 6).

RED

WHITE

100 mm

75 mm

75 mm75 mm

2400 mm

100 mm

Tolerance on alldimensions: ± 5%

Figure 25.1.2 Colouring of buffer beam

B25.1.3 Buffer stop lights Buffer stop lights, where provided, shall be coloured red, except:

a) where the buffer stop is in a siding

b) there is a likelihood that a red light might confuse drivers on other lines.

Where both of the foregoing conditions are met, it is permissible for buffer stop lights to be coloured signal white.

Buffer stop lights shall usually take the form of two light units, mounted one above the other. The lower light unit shall be a height of 2400 mm +/- 100 mm above rail level. The spacing between the inner faces of the lower and upper units shall be 150 mm (+/- 10 mm).

The post shall be usually be located so that the stop lights are in the same vertical plane as the stop block, above the centre-line of the track.




2 8 RAILWAY SAFETY


Where the buffer stops are associated with a sand drag, the post shall be located at the start of the sand drag. It shall be hinged at the bottom, secured with a shear pin to allow it to collapse if impacted by a moving vehicle.

Where there is no mains supply available, it is permissible for the stop light to take the form of one battery operated light unit mounted centrally on the stop block buffer beam.

B25.2 Application Buffer stop lights shall be provided at all buffer stops at the end of main signalled

routes, except where the provision of a reflective strip alone is deemed to be sufficient by a Signal Sighting Committee. The justification for granting the exemption shall be recorded as part of the design records.

B26 Colour requirements

B26.1 Colour of aspect and indicator lights The observed colour of the light emitted from signals shall be within the specified chromaticity limits of BS 1376 for colour classes, in accordance with Table 12

Colour Colour Light Signal Semaphore Signal

Junction Indicator

Other Indicators

Main Position Light

Signal Red Class C #1 Class C #2 Class C - Class C #1

Signal Yellow

Class B Class B Class C - Class B

Signal Green Class C - Class C - -

Lunar White - Class C #3 - Class C #3

Signal White - - Class C - Class C Table 12

#1 – The limit towards yellow shall be restricted to y not greater than 0.295.

#2– The limit shall be restricted to y not greater than 0.300 and y not less than 0.280.

#3 – The limit towards yellow shall be restricted to x not greater than 0.420 and the limit towards blue shall be restricted to x not less than 0.300. (This definition does not accord with BS 1376: 1974.)

Further information relating to the various colours and colour classes can be obtained from BS 1376.

The light source used for signal aspects shall appear to the observer to be circular in shape. Mechanical signal spectacle plates shall be shaped to provide the appearance of a circular aspect when viewed along the centre-line for all permitted angles of the signal arm, taking into account the optics of the light source.

B26.2 Surface colours of signal posts, signal heads and semaphore signal arms or discs The face of colour light signal heads and associated indicators shall be matt black, together with any surrounding back board (except that, for SPAD indicators, the surrounding back board shall be blue to BS 381C shade 109).




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All other external surfaces of colour light signal heads and associated indicators shall be silver or grey in colour. It is important for drivers to be able to distinguish between the back of a signal (silver/grey) from the front of an (unlit) signal (black).

Table 13 defines the colours of semaphore signal arms and discs.

Colour BS 381C Shade

Ref. Number Red 537

Yellow 356 White - Black - Grey 693

Table 13

Surface colours of signal posts shall be chosen to assist the driver in locating the signal. The posts shall not be coloured such that they could be seen as being a red, yellow or green signal under any condition of ambient light. Colour light signal posts shall usually be silver or grey. Semaphore signal posts shall usually be white or silver above a point 150 mm (6") above the balance lever and silver, black or grey below this point.

The mounting brackets, balance arms, and lamp cases at the rear of semaphore signals shall be coloured silver, grey or black at the rear. Disc type shunting signal back blinds shall be painted white.

Semaphore signal sighting boards shall be white at the front and silver, grey or black at the rear.

GK/RT0037 contains details regarding the use of colour on signal posts and gantries as a SPAD prevention measure.

B26.3 Colours of signals constructed as signs Signals constructed as signs eg fixed distant boards shall use contrasting colours from BS 5378 according to their meaning/purpose, in accordance with Table 14.

Safety colour shade

[BS 381C] [BS 4800 when retro–

reflective]

Meaning/purpose

Red [BS 381C – 537] [BS 4800 – 04E53]

Stop Limitation (prohibition or restriction)

Yellow [BS 381C – 355] [BS 4800 – 08E51]

Caution, risk of danger

Grey [BS 381C – 693]

Rear of sign (ie not applicable when viewed from this direction).




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Table 14 B27 Equipment

performance requirements

B27.1 General Signals and indicators shall be readable (as defined in section B27.2) when viewed along the centre-line at the distances shown in Table 15.

Performance category

Readable distance (metres)

Category 1 800

Category 2 250

Category 3 100

Category 4 400

Table 15

The spread of light at the angles to the centre-line shall:

a) be sufficient to meet the readability requirements of GK/RT0037 (throughout the approach to the signal and when the train is standing at the signal)

b) not be so great as to give an unacceptable risk of the signal being misread by drivers on adjacent lines. It is permissible to provide short-range signals, eg at the exit from loops and sidings, where the provision of a long-range signal could cause confusion with aspects on the running lines (see GK/RT0037).

B27.2 Readability An aspect or indication shall be considered ‘readable’ at a given point only if, in clear weather conditions by day and by night, persons just meeting the eyesight requirements of GO/RT3251 are always able to identify the aspects and indications displayed when viewed from the driving cab.

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

The brightness levels of aspects and indications shall be such that where aspects and indicators can be lit simultaneously, no one aspect or indication shall make another unreadable when observed from the readable distance of the shorter range aspect or indication.

B27.3 Mounting Signals, indicators and signs that perform the function of signals shall be rigidly mounted to ensure that they do not become misaligned (eg by being secured on two posts) or deflect from their designed alignment under any usual wind loading.

Under exceptional wind loadings, it is permissible for signals and indicators to deflect, but shall return to their designed alignment when the loading ceases.

Signals and indicators shall not deflect as a result of turbulence from trains passing on adjacent lines.

Arrangements for maintenance purposes (including cleaning of translucent surfaces) shall be provided to front and back of signals and indicators.




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B27.4 Standard performance requirements for signals and indicators The standard performance requirements for each type of signal and indicator are defined in Table 16.

Signal / Indicator Standard Performance Requirements Colour Light Signal Category 1 Short Range Colour Light Signal

Category 2

Colour Light Splitting Distant Signal

Category 1

Co-Acting Signal See section B6.1 Banner Repeating Signal Category 2 or Category 3 - see section B7.2 (Application)

for constraints on application. Position Light Signal Category 3 Junction Indicator Category 1 Alphanumeric route Indicator

Category 2 or Category 3 - see section B10.2 (Application) for constraints on application. Note that the Category 2 and 3 indicators are referred to as Standard and Miniature Alphanumeric route Indicators respectively.

Points Indicator (for Train Operated Points)

Category 3

Driver’s White Level Crossing Indicator

Category 1

Driver’s Red Level Crossing Indicator

The indicator shall be capable of being visible at a range of 600m (see section B27.6).

Loading / Unloading Indicator

Category 3

SPAD Indicator The indicator shall be capable of attracting the drivers’ attention when lit at distances up to 100m and at angles to the centre-line of up to 30°. Furthermore, it shall be capable of doing so when on the periphery of the drivers’ vision, and in an environment with other bright background lights.

Signal OFF Indicator Category 3 Right Away (RA) Indicator Category 3 Close Doors Indicator Category 3 Barriers Up Indicator Category 3 Stop Board Dimensions and reflectivity are specified in section B19.1. Distant Board Dimensions and reflectivity are specified in section B20.1. Semaphore Stop Signal Category 4. At the exit from loops and sidings, it is

permissible for Category 2 to be used. Semaphore Distant Signal Category 4 Semaphore Subsidiary Signal

Category 3

Semaphore Shunting Signal

Category 3

Buffer Stops Category 3 (where lights provided). Dimensions and reflectivity are specified in section B25.1

Table 16




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B27.5 Speeds at which aspects and indications may be considered readable The maximum speed at which an aspect or indication is readable is determined by the required reading time requirements defined in GK/RT0037 and is therefore dependent upon the particular location of each signal. The limits defined in this section are equipment design requirements.

B27.5.1 Performance category 1 equipment All equipment meeting the requirements of performance category 1 shall be designed to be readable at speeds up to 125 mph.

B27.5.2 Performance category 2 equipment With the exception of the banner repeating signal, equipment which meets the requirements of performance category 2 shall be designed to be used only where the approach speed of trains requiring to read the indication does not exceed 60 mph.

B27.5.3 Performance category 3 equipment With the exception of independent position light signals which are pre-set by a main route, equipment which does not exceed the requirements of performance category 3 shall be designed to be used only where there is no requirement for the aspect / indication to be read at a speed exceeding 15 mph. For this purpose, it is assumed that 15 mph will not be exceeded by:

a) movements contained within the confines of a yard or siding

b) movements starting from rest, or virtually at a stand at a main stop aspect

c) movements proceeding under the authority of a position light aspect.

B27.5.4 Performance category 4 equipment Semaphore main signals shall be designed to be readable at speeds up to 100 mph.

B27.6 Flashing aspects and indications With the exception of the drivers’ red level crossing indicator, all aspects and indications which are required to flash shall do so at a frequency of 60 (± 10) cycles per minute. In each cycle the time for which the display is lit shall be between one half and two-thirds of the total cycle time.

The drivers’ red level crossing indicator shall flash at a frequency of 120 (± 6) cycles per minute. In each cycle the display shall be lit for a nominal 25 milliseconds; the period of illumination shall balance the minimum retention time of the human visual system against the need to minimise current drain on emergency power supplies.

B28 Permitted associations of aspects and

indicators It is permitted for the signals and indicators defined in this document to be associated with each other in order to display the combinations of aspects and indications defined in Table 17. It is not permitted for any aspect or indication to be displayed in association with another except where specifically permitted, and subject to any conditions expressed in the notes to the following table. However, certain associations which are not permitted in the tables may arise under equipment failure conditions, or while signals are clearing; definition of such possibilities does not lie within the scope of this document.




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Primary Permissible combinations of Aspects & Indications #1

Aspect #7

Position Light OFF

Junction Indicator

Standard Route

Indicator

Miniature Route

Indicator

Semaphore Distant

ON

Semaphore Distant

OFF

Semaphore Shunt /

Subsidiary ON

Semaphore Shunt /

Subsidiary OFF

C/L Red Yes No No #3 C/L Yellow No Yes Yes No C/L Double Yellow

No Yes Yes No Semaphore Main Signals

C/L Flashing Yellow

No Yes Yes No shall not be

C/L Flashing Double Yellow

No Yes Yes No associated with

C/L Green No Yes Yes No colour light Position Light ON (Red)

No No No main aspects

Position Light OFF

No No Yes on the same structure

Semaphore Stop ON

Yes #4 No No #5 Yes No Yes Yes

Semaphore Stop OFF

No No Yes No Yes Yes Yes No

Semaphore Distant ON

No No No No Yes #2 Yes #2 No No

Semaphore Distant OFF

No No No No Yes #2 No No No

Semaphore Shunt / Subsidiary ON

No No No No No No Yes #6 Yes #6

Semaphore Shunt / Subsidiary OFF

No No No Yes No No Yes #6 No #6

Table 17 Associations of Aspects and Indicators

Notes: #1 The aspects displayable by a splitting distant signal in which more than one signal head is alight are not

included in the above table. #2 Restricted to semaphore splitting distant signals. #3 Only with position light OFF aspect. #4 It is permissible for position light shunt signals to be provided in lieu of (but not mixed with) semaphore

subsidiary / shunt signals #5 Only with semaphore subsidiary, semaphore shunt or position light signal OFF. #6 Restricted to semaphore multi-arm shunt / subsidiary signals. #7 Although the indications are not directly associated with a colour light aspect, it is permissible for a right away

indicator or a close doors indicator to be mounted adjacent to a colour light signal. A right away indicator shall only display an indication when an appropriate proceed aspect is displayed by the signal.




RAILWAY SAFETY 3 5


References Railway Group Standards and other Railway Group Documents

GA/RT6001 Railway Group Standards Change Procedures

GA/RT6004 Temporary Non-Compliance with Railway Group Standards

GA/RT6006 Derogations from Railway Group Standards

GC/RT5033 Terminal Tracks – Managing the Risk

GE/RT8034 Maintenance of Signal Visibility

GI/RT7004 Requirements for the Design, Operation and Maintenance of Points

GI/RT7006 Risk Assessment to Prevent and Mitigate Overruns

GI/RT7012 Design, Construction and Maintenance of Level Crossings (To be published in 2002)

GK/RT0002 Glossary of Signalling Terms

GK/RT0005 Safety Related Colours for Signalling Application

GK/RT0032 Provision of Lineside Signals

GK/RT0034 Lineside Signal Spacing

GK/RT0037 Signal Positioning and Visibility

GK/RT0207 Signalling Design Production

GO/RT3205 Close Doors (CD) Indicators at Platforms

GO/RT3251 Train Driving

GI/GN7606 Guidance Note: Prevention and Mitigatiion of Overruns – Risk assessment

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.

Other References BS 381C Specification for Colours for Identification, Coding and Special Purposes

BS 873 Specification for Retro-Reflective Material

BS 1376 Specification for Colours of Light Signals

BS 4800 Schedule of Paint Colours for Building Purposes

BS 5378 Safety Signs and Colours

