Railway Signals and Indications

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Questions and Answers

What is the primary function of a Calling-on signal?

To call on the Loco Pilot to draw ahead with caution (correct)

To indicate a diversion in the track

To indicate to the Loco Pilot to proceed with caution

To indicate to the Loco Pilot to stop immediately

Under what conditions can a colour light Distant signal be combined with a Stop signal?

Under approved special instructions (correct)

When the train is approaching a level crossing

Only during peak hours

During maintenance operations

What type of Route Indicator is required for speeds in excess of 15 kmph?

Direction Type Route Indicator (correct)

Any Route Indicator of approved design

Route Indicator with traffic lights

Direction Type Route Indicator with LED Matrix

When two or more lines converge, where should the signals be fixed?

On separate posts Signup and view all the answers

What type of signals are recommended for shunt signals according to signalling principles?

Position Light type Signup and view all the answers

What is the primary consideration for determining the number and height of signals?

Safety and operational requirements Signup and view all the answers

What is the purpose of a Route Indicator?

To indicate the diversion in the track Signup and view all the answers

What is the significance of a Stop signal being 'ON'?

The train should stop immediately Signup and view all the answers

What is the purpose of the arrow on a signal erected on the right-hand side?

To indicate the direction of the applicable line Signup and view all the answers

Under what conditions can two or more signals be combined?

Under approved special instructions Signup and view all the answers

Why should signals be located and aligned in a specific way?

To ensure the best possible view of their aspects to the Loco Pilot Signup and view all the answers

What is the primary purpose of a Stop signal?

To bring the train to a stop Signup and view all the answers

What is the primary consideration for the uniformity of signalling at a station?

Maximum permissible speed of the section Signup and view all the answers

What is the purpose of limiting the size of lamps/LEDs of Subsidiary Signals?

To avoid confusion with Main signals Signup and view all the answers

What is the reason for avoiding the possibility of the aspect of one signal being mistaken for the aspect of another?

To improve safety and operational efficiency Signup and view all the answers

Why should Main signals be of the colour light multi-unit type?

To enhance safety and operational efficiency Signup and view all the answers

Where should the Home Signal be placed in relation to the points?

At least 180 meters in rear of the points Signup and view all the answers

What is the purpose of a Routing Signal?

To protect the adjacent running line or lines Signup and view all the answers

When is a Starter Indicator provided?

Only for long or curved platforms Signup and view all the answers

What is the minimum distance the Home Signal should be placed from the points in certain cases?

300 meters Signup and view all the answers

What is the purpose of an Intermediate Starter Signal?

To protect the points it is in rear of Signup and view all the answers

In what type of territory is the Home Signal placed at a distance of 180 meters from the points?

Single Distant territory Signup and view all the answers

What is the condition for placing the Home Signal at a distance of 300 meters from the points?

Continuous down gradient towards the station Signup and view all the answers

What is the aspect of the Starter Indicator when the concerned Starter is 'ON'?

No light Signup and view all the answers

What is the minimum distance required for the placement of an Advanced Starter Signal from the outermost points in a Single Line section?

120 meters Signup and view all the answers

What is the primary purpose of an Intermediate Block Stop (IBS) signal?

To divide the block section into near halves Signup and view all the answers

At what distance from the gate should a Gate Stop Signal be located in a MACLS territory?

180 meters Signup and view all the answers

What is the recommended spacing between Automatic Block Signals?

1 kilometre Signup and view all the answers

When a Signal is displaying the 'Stop' aspect, what is the minimum aspect that the signal next in rear should display?

Caution Signup and view all the answers

What is the purpose of a marker consisting of a yellow coloured disc with letter 'G' in black on a Gate Stop Signal?

To indicate the signal type Signup and view all the answers

What is the minimum distance required for placing a Multiple Aspect Signal that is required to display a 'Caution' aspect to a train?

1 kilometre Signup and view all the answers

What is the colour of the disc used as a marker on an Intermediate Block Stop (IBS) signal?

White Signup and view all the answers

What is the primary design consideration for signal and interlocking circuits in terms of failure?

To revert to their most restrictive aspect Signup and view all the answers

What type of interlocking installation is based on the Entry/Exit principle?

Route Setting Type Signup and view all the answers

What is the purpose of providing different colours for each track circuit on the Control Panel?

To distinguish between different tracks Signup and view all the answers

What is the primary consideration for providing multiple Control Panels/Control Terminals?

All of the above Signup and view all the answers

What is the purpose of providing inter-slotting controls in installations with multiple Control Panels/Control Terminals?

To prevent simultaneous operation of points and signals Signup and view all the answers

What type of installation is required to have a Dual VDU in lieu of a Control Panel and VDU?

All future installations Signup and view all the answers

What is the primary consideration for the design of the Control Cum Indication Panel (CCIP)?

To display the layout in a well-proportioned manner Signup and view all the answers

What is the primary purpose of providing a Control Cum Indication Panel (CCIP)?

All of the above Signup and view all the answers

Where should the Home Signal be placed in relation to the points in a single distant territory?

At a minimum distance of 180 meters Signup and view all the answers

Under what condition can the Home signal be placed at a distance of 300 meters from the points?

When there is a continuous down gradient between Distant and Home signals Signup and view all the answers

What is the purpose of a Routing Signal?

To indicate the route to be taken Signup and view all the answers

When is a Starter Indicator provided?

Only where essentially required Signup and view all the answers

Where should an Intermediate Starter Signal be placed?

Clear of fouling marks in rear of the points, if any, which it protects Signup and view all the answers

What is the aspect of the Starter Indicator when the concerned Starter is 'ON'?

No light Signup and view all the answers

What is the purpose of a Starter Signal?

To protect the converging line Signup and view all the answers

What is the minimum distance the Home Signal should be placed from the points in certain cases?

180 meters Signup and view all the answers

What is the primary consideration for the uniformity of signalling at a station?

Conforming to the same type and standard as per maximum permissible speed of the section Signup and view all the answers

Why should signals be free from the possibility of phantom indication?

To prevent confusion among loco pilots Signup and view all the answers

What is the purpose of providing an arrow on a signal erected on the right-hand side?

To indicate the direction of the applicable line Signup and view all the answers

What is the primary consideration for determining the location and alignment of signals?

Displaying the best possible view of the signal's aspects to loco pilots Signup and view all the answers

Why should the size of lamps/LEDs of Subsidiary Signals be smaller than that of Main signals?

To prevent confusion between the lights of Main signals and Subsidiary Signals Signup and view all the answers

What is the primary consideration for the type of signals used at a station?

Operational requirements of the station Signup and view all the answers

Why should signals be electrically lit?

To ensure signals are free from the possibility of phantom indication Signup and view all the answers

What is the primary consideration for the number of signals and their height?

Limiting them to what is necessary for safety and operational requirements Signup and view all the answers

What is the primary purpose of slot controls on signals?

To prevent a signal from being turned off unless all controls have been exercised Signup and view all the answers

What is the condition under which the Station Master's control over Home Signals can be dispensed with?

If all reception lines are fully track-circuited from Home Signal to the corresponding Last Stop Signal Signup and view all the answers

What is the primary purpose of providing slot control to the Station Master?

To provide an additional layer of safety in the signaling system Signup and view all the answers

What happens when a controlling agency withdraws its control from a slot?

The signal is replaced to the 'ON' position Signup and view all the answers

What is the purpose of designing slot circuits to be effective for only one train?

To provide an additional layer of safety in the signaling system Signup and view all the answers

What is the significance of a slot once given?

It can only be used for a specific train Signup and view all the answers

Under what condition is the Station Master provided slot control over the Home and Last Stop Signals?

Always, as a standard practice Signup and view all the answers

What is the primary purpose of slot controls in the signaling system?

To increase the safety of the signaling system Signup and view all the answers

What is the prerequisite for commissioning of Electronic Interlocking?

Completion of Outdoor signalling works and System Integrity Tests Signup and view all the answers

What is the purpose of Annexure 7-A1 in IRSEM?

To provide extracts from Rules for Opening of Railway Lines for Isolation Signup and view all the answers

What is the minimum permissible speed for STD IV interlocking?

Up to 160 Kmph Signup and view all the answers

What type of point operation is required for STD III interlocking?

Point Machine Signup and view all the answers

What is the requirement for train detection in STD I interlocking?

On all running lines Signup and view all the answers

What is the requirement for block working in STD IV interlocking?

Permitted, excluding token Signup and view all the answers

What is the requirement for double distant/automatic signalling in STD II interlocking?

Required, except on sections with emergency braking distance of more than 1 km Signup and view all the answers

What is the requirement for mobile train radio communication in STD IV interlocking?

Required Signup and view all the answers

When is a short dead end siding not long enough to permit of vehicles being stabled thereon?

Ordinarily, as it is not designed for stabling vehicles Signup and view all the answers

What is the minimum distance required for a trap to be placed on a dead end siding from the starter signal?

180 meters Signup and view all the answers

When can a train be admitted on to the running line?

When the trap is set and locked against vehicles occupying the further part of the dead end siding Signup and view all the answers

What is the purpose of a sand hump of approved design?

To substitute for adequate distance as provided in rule 3.40(4) of the Indian Railways (Open Lines) General Rules, 1976 Signup and view all the answers

What is the minimum length of a siding required when a sand hump is used?

One rail length Signup and view all the answers

When is Method C used?

When a trap is used Signup and view all the answers

What is the condition for setting the points of the dead end siding for the across over and against the siding?

Before a train is admitted on a line trapped by Method B Signup and view all the answers

What is the primary consideration when using Method B or Method C?

To ensure that trains are not derailed Signup and view all the answers

Study Notes

Signals in General

Multiple Aspect Colour Light Signalling (MACLS) is covered in this chapter.
All signals shall be electrically lit and free from the possibility of phantom indication.

Types of Signals

Main signals: colour light multi-unit type
Shunt signals: Position Light type
Calling on signals: may be provided as per operational needs

Uniformity of Signalling

It is desirable that signalling at all stations and interlocked level crossing gates in a section conforms to the same type and standard as per maximum permissible speed of the section.
Signalling at a station at either end shall also be uniform as far as possible.

Signals Location

Signals shall normally be on the left of, or above the line to which they apply, unless authorized by special instructions to the contrary.
Where signals are erected on the right-hand side, they shall be provided with an arrow, pointing towards the applicable line.
Signals shall be located and aligned to display the best possible view of their aspects to the Loco Pilot of approaching trains.
Signals shall avoid confusion between the lights of Main signals and the lights of Subsidiary signals or any other lights.

Combined Signals

When owing to their location, it is necessary to combine any two signals, one Stop Signal only may be provided under approved special instructions, capable of displaying any or all the following aspects:
- Stop
- Caution
- Attention
- Proceed

Distinction between Signals

Diverging lines: a route indicator of approved design shall be provided, unless otherwise permitted by approved special instructions.
Converging lines: unless otherwise permitted by approved special instructions, the signals shall be fixed on separate posts.

Subsidiary Signals

Calling-on signal: when taken 'OFF' calls on the Loco Pilot of a train to draw ahead with caution, after the train has been brought to a stop even though the Stop Signal above it is at 'ON'.
Advanced Starter Signal: shall be placed outside all connections on the line to which it applies, at a distance of not less than 120 meters from the outermost points in the case of Single Line section.
Gate Stop Signal: shall be located at not less than 180 meters in rear of the gate, which it is protecting.
Intermediate Block Stop (IBS) signal: is the Home signal provided at an Intermediate Block post on a Double Line or Single Line.
Automatic Block Signals: shall be normally located with a spacing of one km from each other, subject to other criteria and headway required.

Aspects-Sequence

When a Signal is displaying the 'Stop' aspect, the signal next in rear shall not display a less restrictive aspect than 'Caution'.
Every Multiple Aspect Signal, which is required to display 'caution' aspect to a train, shall normally be placed at an adequate distance from the next signal in advance.

Operation of Signals & Points - Control Panel

The Interlocking installations are of two types: Route Setting Type i.e.on the basis of Entry/Exit principle, Non-route Setting Type i.e.Route is set with individual operation of points.
The points and Signals shall be operated from a Control panel for Relay Interlocking or Control panel and/or Control Terminal (Video Display Unit (VDU)) for Electronic Interlocking.

Essentials of Signalling

Signals in General

Multiple Aspect Colour Light Signalling (MACLS) is covered in this chapter.
All signals must be electrically lit and free from phantom indications.
Main signals shall be colour light multi-unit type, and shunt signals shall be of the Position Light type.
Calling on signals may be provided as per operational needs.
It is desirable to have uniformity of signalling at all stations and interlocked level crossing gates in a section.

Signals - Location

The number of signals and their height shall be limited to what is necessary for safety and operational requirements.
Signals shall normally be on the left of, or above the line to which they apply, unless authorized by special instructions to the contrary.
Where signals are erected on the right-hand side, they shall be provided with an arrow pointing towards the applicable line.
Signals shall be located and aligned to:
- Display the best possible view of their aspects to the loco pilot of approaching trains.
- Avoid the possibility of the aspect of one signal being mistaken for the aspect of another.
- Avoid confusion between the lights of Main signals and the lights of Subsidiary signals or any other lights.
The size of lamps/LEDs of Subsidiary Signals shall be smaller than that of Main signals.

Home Signal

The Home Signal shall be placed at not less than 180 meters in rear of the points up to which the line may be obstructed, after line clear has been granted to the station in rear.
Exceptions:
- Where there is a continuous down gradient towards the station steeper than 1 in 260 between Distant and Home signal in single distant territory and between Inner Distant and Home Signal in Double Distant territories.
- The Home signal may be placed at a distance of sum of Block Overlap and Signal Overlap from BSLB (Block Section Limit Board) or the outermost Facing Point.

Other Signals

Routing Signal: A Routing Signal shall be placed in rear of the Points, which it protects.
Starter Signal: When one Starter Signal is provided for each converging line, it shall be so placed as to protect the adjacent running line or lines.
Intermediate Starter Signal: An Intermediate Starter Signal shall be placed clear of fouling marks in rear of the points, if any, which it protects.

Slot Controls on Signals

Where a signal is controlled through slots, it shall not be possible to take 'off' a signal unless all the controls have been exercised by the controlling agencies.
Slot circuits shall be so designed that a slot once given is effective for only one train and a fresh slot has to be given for a subsequent train.
Station Master's Slot Control on Reception & Dispatch signals.

Commissioning of Electronic Interlocking

On completion of Outdoor signalling works and Electronic Interlocking works, System Integrity Tests (SIT) shall be done before commissioning.
Drawings for Guidance on Installation are given at Appendix II.
Maintenance Schedules are given at Appendix I for various signalling equipments.

Important Minimum Signalling Features

Minimum signalling features shall be provided at various stations based on the standard of interlocking.
The features include:
- Maximum permissible speed
- Isolation
- Point Operation, Locking, and Detection
- Train Detection
- MACLS Signalling, Movement authority
- Block Working
- Double Distant/Automatic Signalling
- Last Vehicle verification
- Relay/Electronic Interlocking
- Mobile Train Radio Communication (MTRC) or LTE or any other Technology
- ATP (ETCS/TCAS/TPWS) with Cab Signalling for SPAD mitigation
- Centralised Traffic Control (CTC)

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This quiz covers the rules and aspects of combined railway signals, including stop, caution, attention, and proceed signals.