Railway Signaling Systems

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Questions and Answers

What is the primary requirement for all signals according to 7.1.2?

All signals shall be electrically lit and free from the possibility of phantom indication.

Describe the uniformity requirement for signalling at all stations as stated in 7.1.4.

The signalling at all stations and interlocked level crossing gates must conform to the same type and standard based on the maximum permissible speed for the section.

According to 7.1.5, where should the signals normally be located in relation to the line they apply to?

Signals shall normally be on the left of, or above the line they apply to.

What does 7.1.6 specify about the design and location of signalling equipment?

All equipment must be designed, located, and secured to minimize the possibility of outside interference. Signup and view all the answers

How should non-operational signals be identified according to 7.1.7?

Non-operational signals shall be distinguished by two crossed bars, each at least one metre long and 10 cm wide, and they shall not be lit. Signup and view all the answers

What is the minimum block overlap distance for multiple-aspect signalling as mentioned in 7.1.8?

The block overlap shall not be less than 180 metres. Signup and view all the answers

What stipulation is made regarding the size and brightness of subsidiary signals compared to main signals in 7.1.5?

The size of lamps/LEDs of subsidiary signals shall be smaller than that of main signals, and subsidiary signals shall not be brighter than main signals. Signup and view all the answers

What precaution is mentioned regarding the alignment of signals in 7.1.5?

Signals should be aligned to display the best possible view of their aspects and to avoid confusion between different signals. Signup and view all the answers

What is the minimum adequate distance for two-aspect signalling?

400 metres. Signup and view all the answers

For multiple-aspect signalling, what is the minimum adequate distance required?

180 metres. Signup and view all the answers

What is the minimum signal overlap required beyond a Home signal?

120 metres. Signup and view all the answers

Under what condition can a Home signal be taken 'off' without the train coming to a stop?

If the line is clear for an adequate distance beyond the Starter. Signup and view all the answers

What is the required visibility distance for a Distant Signal?

400 metres. Signup and view all the answers

What aspect does a Distant Signal display for the 'Caution' indication in single distant territory?

A yellow light in the 'ON' position. Signup and view all the answers

What is the visibility requirement for All Stop Signals?

200 metres. Signup and view all the answers

What does a signal displaying a red light indicate?

Stop. Signup and view all the answers

What aspect should an Inner Distant signal show for the 'Caution' indication?

A yellow light in the 'ON' position. Signup and view all the answers

What additional requirement is there if continuous visibility of 400 metres is not achievable?

A suitable speed restriction may be imposed. Signup and view all the answers

In a Class C station, what indicates that the line is clear?

The whole of the last preceding train must have passed at least 400 metres beyond the home signal. Signup and view all the answers

What is required for a Home signal to be taken 'off' after a train has stopped?

The line must be clear up to the Starter. Signup and view all the answers

What aspect do Stop Signals display for the 'Proceed' indication?

A green light. Signup and view all the answers

What does a yellow light indicate when displayed by a Stop Signal?

Caution. Signup and view all the answers

What is the minimum distance a Distant Signal should be placed in rear of the first Stop Signal in Single Distant Territory?

Not less than 1 kilometre. Signup and view all the answers

In Double Distant territories, how far should the second Distant Signal be from the first Stop signal?

At least 2 kilometres. Signup and view all the answers

What type of marker identifies Distant and Inner Distant Signals?

A white coloured disc with the letter 'P' in black. Signup and view all the answers

How far should the Home Signal be placed in rear of the points it protects?

Not less than 180 metres. Signup and view all the answers

Under what condition can the Home Signal be placed at a distance less than 180 metres?

If there is a continuous down gradient steeper than 1 in 260. Signup and view all the answers

What is the purpose of a Routing Signal?

To protect the points it refers to. Signup and view all the answers

When should an Advanced Starter Signal be located at a distance of not less than 120 metres?

In the case of Single Line sections. Signup and view all the answers

What is the minimum spacing requirement for Automatic Block Signals?

Typically one kilometre from each other. Signup and view all the answers

What aspect must the signal next in rear of a displaying 'Stop' aspect show?

It must not display a less restrictive aspect than 'Caution'. Signup and view all the answers

What condition applies to Multiple Aspect Signals displaying a 'Caution' aspect?

They should normally be placed at a distance of not less than 1 kilometre from the next Signal in advance. Signup and view all the answers

In case the adequate distance for a 'Caution' aspect is not possible, what must the next signal in rear display?

'Attention'/'Caution' aspect. Signup and view all the answers

What does the Intermediate Block Stop (IBS) signal signify?

It is the Home signal provided at an Intermediate Block post. Signup and view all the answers

What type of marker does a Gate Stop Signal have?

A yellow coloured disc with the letter 'G' in black. Signup and view all the answers

What must be done if the signal cannot be placed sufficiently in rear of the 'STOP' signal protecting diverging lines?

The 'Attention'/'Caution' aspect must be repeated back on successive signals in rear. Signup and view all the answers

What is the role of a Starter Signal in rail signaling?

It protects the adjacent running line or lines when placed correctly. Signup and view all the answers

What must the next signal in rear display when the adequate distance cannot be provided?

The next signal in rear must display the 'attention/caution' aspect. Signup and view all the answers

What is the maximum type of signal aspects that a combined signal can display?

A combined signal can display any or all of the following aspects: Stop, Caution, Attention, and Proceed. Signup and view all the answers

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

A Direction type Route Indicator is required for up to 3 diversions on any side of the main line. Signup and view all the answers

What does a Calling-on signal indicate to the Loco Pilot when taken 'OFF'?

It indicates that the Loco Pilot should draw ahead with caution after stopping, despite the Stop Signal being 'ON'. Signup and view all the answers

How many lights does a Position Light Shunt Signal display in the 'ON' position?

A Position Light Shunt Signal displays two horizontal lights in the 'ON' position. Signup and view all the answers

What functionality does a Shunt Signal provide in terms of track safety?

A Shunt Signal locks and detects all the points in the route and ensures the tracks are clear. Signup and view all the answers

What is required of Calling-on Signals regarding level crossing gates?

All level crossing gates in the route must be closed and locked against road traffic. Signup and view all the answers

What aspect does a Calling-on signal display when it is in the 'ON' position?

It displays no light in the 'ON' position. Signup and view all the answers

What should a Shunt Signal show when placed below a Stop Signal?

The Shunt Signal should show no light in the 'ON' position. Signup and view all the answers

When should track circuits be provided for Calling-on Signals?

Track circuits should be provided at a suitable distance to ensure the train has stopped before the Calling-on Signal is taken 'OFF'. Signup and view all the answers

What should be included in the concerned Station Working Rules for Calling-on Signals?

Provision for manual replacement of Calling-on signals should be included. Signup and view all the answers

What happens to a Calling-on Signal when it is below a Stop Signal?

It cannot be operated at the same time as the Stop Signal above it. Signup and view all the answers

What distinguishes converging lines in terms of signal placement?

Signals must be fixed on separate posts unless otherwise permitted by approved special instructions. Signup and view all the answers

What is a feature of a colour light Calling-on signal in the 'OFF' position?

It displays a miniature yellow light in the 'OFF' position. Signup and view all the answers

Study Notes

Multiple Aspect Colour Light Signalling (MACLS)

All signals must be electrically lit, eliminating phantom indications.
Main signals are multi-unit colour light; shunt signals are position light. Calling signals are optional based on operational needs.
Signal types and standards should be uniform across stations and level crossings within a section, matching the section's maximum permissible speed. End-station signaling should be consistent as much as possible.
Signal numbers and heights should be kept to a minimum necessary for safety and operation.
Signals are typically on the left or above the relevant track; right-hand signals have directional arrows.
Signal placement and alignment prioritizes: clear visibility for approaching locomotives; minimizing the chance of one signal aspect being confused with another; and avoiding confusion between main, subsidiary, or other lights. Subsidiary signal lamp size/LEDs should be smaller than main signals and not brighter.

Signal Location and Spacing

Block overlap must be at least 180 meters for MACLS.
Signal overlap must be at least 120 meters. Method of reckoning is detailed.
Overlap beyond the IB signal (Class C station) must be at least 400 meters beyond the IB home signal. Specific rules are defined.
Signals must offer minimum visible distance: 400 meters for distant signals; 200 meters for stop signals. Visible distance limitations should be accompanied by speed restrictions. Inner distant signals visible from 200 meters.

Signal Aspects

Distant signal aspects differ in single and double distant territories.
- Single distant: yellow (bottom) for caution; two vertical yellow lights for attention; green for proceed.
- Double distant: two vertical yellow lights for attention; green for proceed. Inner distant signal displays aspects as in single distant territory. Special instructions may allow combining the distant signal with other signals.
Stop signal aspects: red for stop; yellow for caution; two vertical yellow lights for attention; and green for proceed.
Typical station signal aspects are outlined. Detailed descriptions are given for different situations (e.g., main line, loop line).

Distant signals are placed a considerable distance behind the first stop signal (at least 1 kilometer in single distant, 2 kilometers for doubled distant and 1 kilometer distance for inner) in consideration of emergency braking distances.
Home signal placement is behind any track connections, at least 180 meters from the furthest obstructed point after line-clearance is granted. Special considerations apply for gradients.
Routing signals are placed behind points that control routing.
Starter signals (one per converging line) protect adjacent lines.
Starter indicators (optional) repeat starter aspects.
Intermediate and advanced starter signals placement criteria are detailed for single and double line sections.
Gate stop signals are placed at least 180 meters behind the gates they protect.
Intermediate Block stop signals are at an intermediate block post on double or single line, and are spaced to divide the block section roughly in half.
Automatic signals are spaced approximately one kilometer apart.

Signal Sequence & Coordination

When a stop signal is displayed, signals further back cannot show a less restrictive aspect than caution.
Multiple aspect signals displaying caution must be adequately spaced from the next signal ahead—at least 1 kilometre. Caution aspects are repeated on successive signals for closer distances.
For metro, distances accommodate maximum emergency braking and ruling gradients. Special consideration is provided when signals lack adequate distance in double distant territories.
Combined signals (allowing stop, caution, attention, and proceed aspects) may be provided under special instructions.
Special consideration is given to diverging and converging lines.

Subsidiary Signals

Calling-on signals caution trains to proceed ahead cautiously after stops, even if signals are green. Calling-on signals are indicated by yellow light instead.
Shunt signals control shunt movements. Lights are white and horizontally aligned in the 'ON' position, and diagonal in the 'OFF' position. Signals can be located separately or below stop signals.
Installation methods for calling-on and shunt signals are included.
Detailed rules about timing and operation of signalling for calling-on signals are listed (including train stops and track circuits).

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Description

This quiz covers the fundamentals of Multiple Aspect Colour Light Signalling (MACLS) used in railway systems. It highlights the importance of uniform signal standards, visibility, and safety in signal placement. Test your knowledge on the operational needs and types of signals in railway networks.