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This document is the property of Railtrack PLC. It shall not be reproduced in whole or in part without the written permission of the Controller, Railway Group Standards, Railtrack PLC. Published by: Safety & Standards Directorate Railtrack PLC Floor DP01, Railtrack House Euston Square London NW1 2EE © Copyright 1999 Railtrack PLC Railway Group Standard GK/RT0035 Issue Two Date October 1999 Layout of Lineside Signals Synopsis This document contains the mandatory requirements for the positioning of signals in relation to other parts of the railway infrastructure. Submitted by Elizabeth Fleming Standards Project Manager Authorised by Brian Alston Acting Controller, Railway Group Standards Withdrawn Document Uncontrolled When Printed
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Page 1: #GKRT0035 Iss 2_Layout of Lineside Signals

This document is the property of Railtrack PLC. It shall not be reproduced in whole or in part without the written permission of the Controller, Railway Group Standards, Railtrack PLC. Published by: Safety & Standards Directorate Railtrack PLC Floor DP01, Railtrack House Euston Square London NW1 2EE © Copyright 1999 Railtrack PLC

Railway Group Standard GK/RT0035 Issue Two Date October 1999

Layout of Lineside Signals

Synopsis This document contains the mandatory requirements for the positioning of signals in relation to other parts of the railway infrastructure.

Submitted by Elizabeth Fleming Standards Project Manager

Authorised by Brian Alston Acting Controller, Railway Group Standards

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R A I L T R A C K 1

Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 1 of 13

Contents Section Description Page

Part A

Issue Record 2 Responsibilities 2 Compliance 2 Health and Safety Responsibilities 2 Supply 2

Part B

1 Purpose 3 2 Scope 3 3 Definitions 3 4 Principle 3 5 General Requirements 3 6 Signals Authorising Shunting Movements and Movements onto Occupied Lines 6 7 Banner Repeating Signals and Signal Off Indicators 6 8 Constraints on Signal Position 7 9 Junction Signalling 9 10 Bi-Directional Signalling 11

References 13

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2 R A I L T R A C K

Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 2 of 13

Part A

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

Amended or additional parts of revised pages will be marked by a vertical black line in the adjacent margin.

Issue Date Comments One Two

September 1996 October 1999

Original Document. Supersedes SSP6, SSP11 (Sections 1, 2, 3, 4 and 5 only), SSP28, SSP48 (Sections 1, 2, 4, 5 and 6 only), SSP57 (Section 1 only), SSP58, SSP64, SSP76 (Section 1 only). This issue is a complete rewrite and supersedes all parts of issue 1 and SSP 061. Thus it was not appropriate to denote changes by a vertical black line in the adjacent margin.

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 and the duty holders of the Railway Safety Cases accepted by Railtrack.

Compliance

The provisions of this document are to be complied with for schemes for which the Signalling Scheme Plan is first approved on or after 4 December 1999. Retrospective action is not required in respect of existing layouts or for schemes for which the Signalling Scheme Plan was approved prior to 4 December 1999. Railtrack shall consider the need to comply with this issue of the Standard when any alterations are made to a Signalling Scheme Plan which had first been approved prior to 4 December 1999.

Health and Safety Responsibilities

In issuing this document, Railtrack PLC makes no warranties, express or implied, that compliance with all or any documents published by the Safety & Standards Directorate 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.

Supply

Controlled and uncontrolled copies of this document may be obtained from the Industry Safety Liaison Dept, Safety and Standards Directorate, Railtrack PLC, Railtrack House, DP01, Euston Square, London, NW1 2EE.

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R A I L T R A C K 3

Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 3 of 13

Part B

1 Purpose The purpose of this document is to define the requirements for the provision and use of lineside signals for the protection of trains and railway infrastructure where these are the means by which train movements are to be controlled.

2 Scope The overall scope of Railway Group Standards is as specified in Appendix A of GA/RT6001.

Specifically the contents of this document encompass requirements for positioning of signals in relation to infrastructure and requirements for indication of route information. Indicators and signs having the function of signals are included where appropriate.

The requirements of this document apply to all running lines where lineside signals are the means of controlling the passage of trains.

3 Definitions Platform Starting Signal A signal which must be seen to be “OFF” before a train is permitted to start from a platform.

SLU Sign A sign indicating the number of “Standard Length Units” beyond a particular point, typically used to aid drivers in determining where to stop a movement which is to reverse over a trailing connection.

Stop Signal For the purposes of this document, a Stop Signal may include a stop board, a block limit marker board, a buffer stop, a points set indicator or a remote ground frame marker board.

4 Principle Lineside signals shall be positioned to give a clear and unambiguous information to the driver, in such a way that the overall risk to infrastructure, train movements and personnel is as low as is reasonably practicable.

At junction signals, a clear and unambiguous route indication shall be provided.

5 General Requirements The requirements for provision of signals in this section apply equally to lines signalled for unidirectional and bi-directional working.

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

The method of block signalling adopted for a section of line shall take into account the nature of traffic, including speed, frequency and operability, and shall be a method specified in one or more of the following Group Standards:

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

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Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 4 of 13

The method of block working in use shall be reviewed if traffic flows change significantly from the design level or the level last assessed.

Requirements for signal positioning specific to the method of block working to be used on the section of line to which the signal applies are stated in the Group Standards related to those methods of working.

5.2 Moveable Components of the Infrastructure 5.2.1 Where it is possible to break the continuity of the line of way under normal operational circumstances (e.g. at points and moveable bridges), a protecting stop signal shall be provided on each line on which signalled movements may approach the discontinuity of the permanent way. In the case of train operated facing points, or where lineside signals are not otherwise required (eg RETB) a Points Indicator is an acceptable substitute for a stop signal.

5.2.2 Where points are controlled by a ground frame, the provision of protecting signals is not mandatory for movements which are under the exclusive control of the person operating the ground frame.

5.3 Conflicting Movements Protecting stop signals shall be provided on every line on which signalled movements may approach a place of conflict, so that:

• trains may be given movement authority when a movement is to be made; • trains not having movement authority may be stopped clear of any conflicting

movement. Where points are controlled by a ground frame, it is not necessary to provide signals solely to prevent conflict between movements which are under the exclusive control of the person operating the ground frame, or to prevent conflict with a running movement along the main line which requires the ground frame to be locked in the normal position.

5.4 Signals at Point of Reversal Where trains are required to reverse (except on single lines worked by any system of control other than Track Circuit Block), a stop signal shall be provided at the point of reversal to authorise the movement in the reverse direction. The risks resulting from the outward movement proceeding too far beyond the point of reversal shall be assessed, and consideration shall be given to repositioning the reversing movement signal or providing additional controls to hold the route between the point where the outward movement might stop and the signal controlling the reversal. The risk of the outward movement not coming wholly within the signal controlling the reversal shall also be assessed and the train detection boundary shall be placed as close as practicable to the reversing movement signal (this requirement taking precedence over the usual requirement for positioning boundaries beyond signals).

A marker sign, such as a multiple-unit car stop or SLU sign, may be provided at the outward stopping point to aid the driver. These signs shall not define the limit of movement authority for the outward movement. 5.5 Level Crossings Where a level crossing is required to be protected by interlocked signals, a stop signal shall be provided on every line on which movements approach the crossing.

5.6 Lockout Systems Where a lockout system for protection is provided, a stop signal shall be provided on every line on which signalled movements may approach the area protected by the lockout system.

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R A I L T R A C K 5

Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 5 of 13

5.7 Line Capacity Signal positions shall be selected to deliver the required capacity and permissible linespeed, subject to the requirements detailed in:

• Section 8 of this document; • GK/RT0032, Lineside Signal Aspect Sequences; • GK/RT0034, Lineside Signal Spacing; • GK/RT0044, Controls for Signalling a Train onto an Occupied Line

5.8 Designation of Signals All main signals shall be designated controlled except where the criteria for designation as an automatic, semi-automatic, intermediate block home or distant signal are met.

The designation of signals shall be indicated to the driver using the signs defined in GK/RT0033, Lineside Signs.

5.8.1 Automatic Signals in Track Circuit Block Areas A signal may be designated automatic where no significant hazard would arise from the driver passing a signal at danger under his own authority in the event of failure of communication. A significant hazard shall always be considered to exist in the following situations:

• where the signal protects points within the route up to the following signal. Points within the overlap which is beyond the following signal are not considered to be a hazard for these purposes;

• where the layout is such that opposing direction signalled movements would enter the route or overlap;

• where the signal protects other hazardous features of the permanent way (eg a moveable bridge), or prevents conflicting movements;

• where the signal protects a manually controlled level crossing; • where the signal is required to be held at red on the approach to an electrical

section which can be isolated.

Where the overlap beyond the following signal contains trailing points which could be in a position other than that required for the overlap, but there is no other significant hazard, the signal may be designated and signed as Automatic although the interlocking system may treat it as controlled.

5.8.2 Semi-Automatic Signals in Track Circuit Block Areas A signal may be designated semi-automatic where no other significant hazard listed in section 5.8.1 exists and it only protects:

• facing points which are locally controlled from a ground frame, provided that the points are within 800m of the signal. Where the distance between the signal and the facing points exceeds 800m the signal shall usually be designated controlled; or

• trailing points locally controlled from a ground frame;

Signals (including signals protecting a manually controlled level crossing which can be closed to road traffic for all or part of the day) may also be designated semi-automatic where no other significant hazard listed in section 5.8.1 exists and they are operated from a signal box which can be switched out and for which the automatic mode of operation is adopted during the time that the signal box is switched out.

5.8.3 Intermediate Block Home Signals in Absolute Block Areas A stop signal shall be designated an intermediate block home signal where the signal is provided to enable an additional block section to be controlled by one signal box (under the Absolute Block regulations) and the signal meets the criteria for an automatic signal given in section 5.8.1.

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A signal classified as an Intermediate Block Home Signal shall be indicated to the driver by the use of the “Intermediate Block” signal plate as defined in GK/RT0033, Lineside Signs.

5.8.4 Semaphore Stop Signals All semaphore stop signals shall be classified as controlled for signallers’ purposes and non-passable for drivers’ purposes, with the sole exception of those classified as intermediate block home signals, for which section 5.8.4 applies.

5.8.5 Distant Signals Main signals not capable of displaying a stop aspect shall be designated as distant signals.

6 Signals Authorising Shunting Movements and Movements onto

Occupied Lines 6.1 Associated with a Main Signal Where a shunting movement or a calling-on movement onto an occupied line is required from a position at which a main signal is provided, a position light signal or semaphore subsidiary signal (as appropriate) shall be provided in association with the main signal.

Where a shunting movement is made from a main signal, and the movement authority is available including the overlap at the next main signal, the movement shall normally be made under the authority of the main signal aspect. Exceptionally, a movement for shunting purposes may be made under the authority of a position light or semaphore subsidiary signal on a route for which a main signal aspect could be given. The meaning of the aspect displayed to the driver shall be consistent with the definition in GK/RT0031, Lineside Signals and Indicators.

6.2 Not associated with a Main Signal Where there is no requirement for a running signal, shunt signals shall fulfil the requirements of sections 5.2, 5.3, 5.4, 5.5 and 5.6. A position light signal or semaphore shunt signal (as appropriate) shall be provided.

6.3 Destinations For the purposes of signalling layout design, a calling-on class route shall read up to a main signal or a buffer stop.

For the purposes of signalling layout design, a shunt class route shall read up to one of the following: a main signal, a position light or semaphore shunt signal, a limit of shunt indicator, a stop board or a buffer stop.

7 Banner Repeating Signals and Signal Off

Indicators 7.1 Banner Repeating Signals Banner repeating signals shall be provided in accordance with the applications listed in GK/RT0031, Lineside Signals and Indicators. The necessity of providing a banner repeating signal shall be determined primarily by a Signal Sighting Committee.

7.2 Signal Off Indicators Signal off indicators shall be provided in accordance with the applications listed in GK/RT0031, Lineside Signals and Indicators. The necessity of providing a signal off indicator shall be determined primarily by a Signal Sighting Committee.

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Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 7 of 13

8 Constraints on Signal Position

A signal sighting committee shall determine the exact position of any new signal. The chosen location shall take into account the constraints imposed by this section and other Railway Group Standards.

8.1 Position of Signals Relative to Layout and Other Signalling Equipment Positioning of signals relative to signs shall ensure that conflicting or confusing information is not displayed.

8.1.1 Facing Points Where a signal reads over facing points, the signal shall not be positioned more than 800m from the first set of facing points, except as stated below, and shall be sufficiently close to the points that:

• the driver's opportunity to forget the route indicated before reaching a divergence is kept to a minimum;

• the driver's opportunity to accelerate before reaching a divergence after being approach controlled is kept to a minimum.

The preceding requirement does not apply where:

• the points are operated from a ground frame;or • the signal is positioned parallel with one or more signals, one of which is

within 800m of the relevant junction and other constraints prevent the positioning of all signals closer to the junction; or

• the points are secured out of use; or • the excess distance arises as a temporary consequence of stage-works, and

an appropriate warning is published to all drivers using the route throughout the duration of the stage-works.

8.1.2 Avoidance of Fouling Wherever practicable, stop signals shall be positioned such that any overlap which is required at that signal for routes reading up is it does not infringe on points or a level crossing, and such that a train stopped at the signal does not stand over a level crossing or points, or foul another line. Where catch points are provided, it shall be ensured that they are positioned in excess of the maximum train length limits for the line on the approach to the signal.

8.1.3 Passenger Permissive Movements The risk of the driver failing to stop short of another vehicle in the section may be reduced by minimising the distance from the signal giving permissive movement authority to the closest portion of line which may be occupied in accordance with the requirements of GK/RT0044, Controls for Signalling a Train onto an Occupied Line.

8.1.4 Signals on Parallel Tracks Where there are signals on parallel tracks for movements in the same direction, they shall be positioned to minimise the likelihood of the driver mistaking a signal on a parallel line as being applicable to the line the train is on, or mistakenly believing a signal to be applicable to a parallel line.

Semaphore and colour light signals shall not, however, be intermixed.

8.1.5 Automatic Warning System The position of a signal shall not be constrained by the need to avoid conflict with any unsuppressed Automatic Warning System (AWS) magnet which applies to a signal for movements in the opposite direction. The requirements for the positioning of AWS magnets are subordinate to the requirements for the positioning of stop signals. More detailed requirements for the positioning of AWS magnets are included in GK/RT0016, Automatic Warning System of Train Control (AWS).

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Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 8 of 13

8.1.6 Positioning of Stop Boards Where authority to pass a stop board is given by a shunter or person in charge, the stop board shall be positioned such that this authority can be communicated from the usual working position of the shunter or person in charge. Exceptionally, where this is not practicable, means of communicating directly with the shunter or person in charge shall be provided, or the stop board shall be replaced by a signal.

Whenever alterations to the method of working are proposed, the position(s) of stop board(s) and associated communications facilities shall be reviewed to ensure that safe operation is maintained.

8.2 General Constraints on Positions at which Trains may be Stopped Stop signals shall be positioned to minimise the risk of a passenger train stopping in a hazardous location (e.g. a viaduct, a tunnel or a high embankment). Where a signal is required at a hazardous location in order to maintain headway, special controls shall be considered to minimise the risk of a train being stopped at the signal. Particular consideration shall be given to the effect on headway where special controls are applied affecting two or more consecutive signals in a tunnel or on a viaduct.

Special controls need not be applied where the risks associated with trains stopping in tunnels or on viaducts are controlled by other means, such as central door locking or power-operated doors on all trains.

Where practicable, stop signals shall be positioned such that trains are not:

• required to stop on severe gradients; or • required to stop at known leaf fall sites; or • required to stop where noise nuisance would be caused.

8.3 Position of Signals Relative to Platforms Signals shall be positioned to minimise risk taking into account the additional hazards from a passenger train without central door locking or power-operated doors being brought to a stand at a signal with a platform adjacent to only part of the train.

Where a passenger train stopped at the first signal reached after setting off from a platform would lie partially adjacent to the platform, the signal shall be considered to be a platform starting signal.

Platform starting signals shall be readable by the driver while the train is standing at the platform. Where this would otherwise be difficult to achieve, a banner repeating signal or off indicator shall be used.

The risks resulting from a train starting from a station when the platform starting signal is displaying a stop aspect shall be assessed in accordance with GK/RT0078, Overrun Protection and Mitigation.

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Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 9 of 13

8.4 Hazards Affecting the Driver Where practicable, stop signals shall be positioned such that the driver is not exposed to hazards such as live dc traction rails when leaving the cab of a train stopped at the signal.

Group Standard GO/RT3000, Master Rule Book, Section K, defines the requirement that 'the signaller must be reminded about the presence of a train which is detained at a signal at Danger or a shunting move which is detained.' GK/RT0033, Lineside Signs, defines the requirements for signs associated with signals which convey information to the driver relating to this need to communicate with the signaller.

Lineside signals capable of displaying a stop aspect shall be positioned so that the exposure of the driver to hazard whilst communicating by Signal Post Telephone is minimised.

8.5 Electrification Constraints Railtrack shall ensure that the arrangement of the electrification systems and signalling systems are considered together to ensure the optimum combination is achieved.

8.5.1 Overhead Electrification Systems On lines electrified on the overhead system, stop signals shall normally be located sufficiently far from a neutral section to ensure that:

• an electric train with only one pantograph is not brought to rest with its pantograph in the neutral section;

• an electric train restarting from a signal is not liable to stall in the neutral section, with allowance being made for the ruling gradient and the attainable speed.

Stop signals shall be located a sufficient distance (normally at least 100m) on the approach side of Booster Transformers, Sectioning Switches and Track Sectioning Cabins not fitted with neutral sections, and a sufficient distance on the departure side to ensure that no pantograph bridges the overhead line insulated overlap when travelling slowly or stationary.

In order to ensure that these requirements are fully complied with, it shall be necessary to consider the positions of the pantographs on all types of stock which are permitted to use the line.

8.5.2 Conductor Rail Electrification Systems On lines electrified with conductor rail systems, stop signals shall be positioned to minimise the likelihood of trains becoming isolated in gaps where the conductor rail is not continuous. Where there is a gap between two sections of conductor rail which may be isolated from each other by remote switching, stop signals shall be positioned to ensure that it is not possible for a train stopped at a signal to bridge the gap.

9 Junction Signalling Wherever a signal protects:

• any facing points over which more than one main route is available, or • facing points immediately ahead of the signal where the straight ahead route

is not a signalled route, although it would appear to the driver to be an available route,

it shall be regarded as a junction signal and shall be subject to the requirements defined in this section.

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9.1 Indication of Route The route set at a colour light junction signal shall be indicated to the driver by means of a Junction Indicator or Alphanumeric Route Indicator in association with the junction signal (displayed in accordance with the principles defined in GK/RT0031, Lineside Signals and Indicators). The choice of indicator type (i.e. Junction Indicator or Alphanumeric Route Indicator) shall be constrained by the readability performance of the indicator for the ruling linespeed.

The route set at a semaphore junction signal shall be indicated to the driver by means of multiple semaphore arms (displayed in accordance with the principles defined in GK/RT0031, Lineside Signals and Indicators), and/or by an Alphanumeric Route Indicator in association with a single semaphore arm.

Where required by GK/RT0031, Lineside Signals and Indicators, the route set at a position light signal or semaphore shunt signal shall be indicated to the driver by a Miniature Alphanumeric Route Indicator.

9.2 Approach Control and Advance Warning of Divergence Where any safety hazard would arise through the driver being unaware that a diverging route is set until within sight of the route indication at the junction signal, either approach control or advance indication of divergence shall be employed to ensure an adequate reduction in train speed. In semaphore signalling, approach control may be manually implemented by the signaller, in accordance with appropriate operating instructions.

Where advance indication of diverging route is required in colour light signalling, it shall be achieved by means of a flashing aspect or splitting distant aspect sequence (these sequences are defined in GK/RT0031 Lineside Signals and Indicators and GK/RT0032 Lineside Signal Aspect Sequences).

Where advance indication of diverging route is required in semaphore signalling, semaphore or colour light splitting distant aspects may be used on approach to any semaphore junction signal (these sequences are defined in GK/RT0031 Lineside Signals and Indicators and GK/RT0032 Lineside Signal Aspect Sequences).

9.3 Approach Control from Yellow Approach control from yellow (without a flashing yellow aspect sequence) may be used only where the following conditions are satisfied:

• the permissible speed of the divergence, and the distance to the signal immediately beyond the divergence on the unrestricted route, are such that any train receiving cautionary aspects for that signal can be controlled to observe the permissible speed of the divergence;

• no safety hazard would arise as a result of a train being misrouted.

9.4 Flashing Yellow Aspects A flashing yellow aspect sequence may be used on the approach to any colour light junction signal. A signal shall not be capable of displaying a single flashing yellow aspect reading up to one junction and a double flashing yellow aspect reading up to a second junction.

Flashing yellow aspect sequences may read up to more than one route from a junction, provided the divergences are sufficiently similar in speed for the driver to adequately control the train after reading the route indicator on the junction signal.

Where the speed of the diverging route is less than the speed of the fastest route, the provisions of GK/RT0038, Speed Restrictions, shall be followed.

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9.5 Colour Light Splitting Distant Aspects A splitting distant aspect sequence may only be used on the approach to a colour light junction signal to distinguish between the main route and a single divergence at a junction.

Other routes from the junction signal shall be signalled using Approach Control, without advance warning.

Where the speed of the diverging route is less than the speed of the fastest route, the provisions of GK/RT0038, Speed Restrictions, shall be followed.

10 Bi-Directional Signalling

This section does not apply to adjacent lines signalled as independent single lines.

10.1 Full Bi-Directional Signalling Signals for the normal and reverse directions on bi-directional lines shall be provided in accordance with the requirements of thisdocument. The method of Block Signalling shall be the same on each line and signals shall be positioned parallel to each other. Signalling on the reverse direction line may have fewer aspects than that applicable to the normal direction line provided the line speed is reduced to ensure adequate signal spacing between the first cautionary aspect and the stop signal.

Where Automatic Warning System (AWS) is provided at the normal direction signals, it shall be provided at all reverse direction signals. AWS at signals in each direction shall be suppressed for movements in the opposing direction.

10.2 Reduced Capacity Bi-Directional Signalling Where the headway requirement for the reverse direction does not warrant the same signal spacing as provided for the normal direction, a reduced quantity of signals may be provided, with the constraint that consecutive stop signals shall be no more than ten miles apart . All other requirements are the same as for Full Bi-directional Signalling. The reverse direction signals shall be positioned in accordance with the requirements of section 8.1.4.

Caution aspects shall be provided approaching each stop signal appropriate to the standard aspect sequence for the reverse direction capacity and linespeed.

10.3 Simplified Bi-Directional Signalling (SIMBIDS) This form of bi-directional signalling is characterised by the reduced provision of AWS, and shall not be provided for the making of reverse direction moves under normal operating conditions. SIMBIDS shall only be provided on lines worked by track circuit block. AWS requirements for SIMBIDS are defined in GK/RT0016, Automatic Warning System of Train Control (AWS).

Signalling shall otherwise be provided in accordance with section 10.2 of this document, but to control the risks arising from the non-provision of AWS, the following operating restrictions shall apply:

• use shall be confined to situations when otherwise single line working in accordance with GO/RT3000, The Rule Book, would be applied;

• the permissible speed for the reverse direction may need to be lower than that for the normal direction and shall not exceed 70 mph.

The requirement to position SIMBIDS signals parallel to signals for normal direction moves shall take precedence over the maximum signal spacing requirement contained in GK/RT0034, Lineside Signal Spacing, where the spacing for the normal direction move is based on line speeds in excess of that ruling on the reverse direction move.

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Where SIMBIDS is provided, a risk assessment and cost benefit analysis shall be undertaken and recorded to demonstrate that SIMBIDS provides the lowest cost to prevent a fatality. The analysis shall demonstrate that the risks, hazards and consequences have been evaluated. The following factors are the minimum to be considered:

a) human factors associated with the continuous cancellation of AWS warnings, particularly failure to respond at

(i) the reverse direction exit signal: (ii) the signals upon return to normal direction running; (iii) intervening moveable components of the infrastructure, such as

crossovers, level crossings; (iv) permanent, temporary and emergency speed restrictions within the

SIMBIDS section;

b) the ability of drivers to discern the appropriate signal for both normal direction and reverse direction moves;

c) the cautionary aspects displayed approaching reverse direction signals compared to the adjacent line;

d) any extended distance between reverse direction signals compared to the adjacent line, including the reduction in ability to stop trains using signals;

e) lamp out in any main colour light not protected by AWS;

f) overrun by a train towards a route where the entrance signal is at an extended spacing;

g) the increased risk from a safety critical failure;

h) exposure of lineside workers;

i) signaller error, particularly during degraded operations.

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Railway Group Standard GK/RT0035 Issue Two Date October 1999 Page 13 of 13

References

GA/RT6001 Railway Group Standards Change Procedures

GK/RT0016 Automatic Warning System of Train Control (AWS)

GK/RT0031 Lineside Signals and Indicators

GK/RT0032 Lineside Signal Aspect Sequences

GK/RT0033 Lineside Signs

GK/RT0034 Lineside Signal Spacing

GK/RT0037 Signal Sighting

GK/RT0038 Speed Restrictions

GK/RT0041 Track Circuit Block

GK/RT0042 Absolute Block

GK/RT0044 Controls for Signalling a Train onto an Occupied Line (see current Railway Group Standard catalogue for issue status) GK/RT0051 Single Line Control

GK/RT0054 Radio Electronic Token Block

GK/RT0078 Overrun Protection and Mitigation

GO/RT3000 Master Rule Book

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