Signalling Flashcards
What is the principle of absolute block signalling?
One train, one section, one time to keep trains apart and avoid collisions.
What are the drawbacks of absolute block signalling?
Capacity can be limited
What type of signals are used in absolute block signalling?
Semaphore signals or colour lights
What does a semaphore distant signal at caution look like? What does this mean?
Yellow arm with fishtail in horizontal position with yellow light.
Be prepared to stop at the next stop signal- all associated stop signals will be at danger
What does a semaphore distant signal at clear look like? What does this mean?
Yellow arm with fishtail at 45 degrees with green light.
All associated stop signals will display proceed aspects.
What does a semaphore stop signal look like at danger? What does this mean?
Red horizontal arm with red light.
You must stop at this signal
What does a semaphore stop signal look like at proceed? What does this mean?
Red arm at 45 degrees with green light.
You may proceed past this signal.
Do you get AWS magnets before semaphore stop and distant signals?
Only 180m before semaphore distant signals. Not before stop signals.
What distance are distant signals from stop signals?
Service braking distance
What are your actions if the stop signal changes from danger to proceed after receiving a cautionary distant signal?
Proceed but expect the next stop signal to be at danger.
What are station limits?
The section between the signal box’s first signal (home signal) and last signal (section signal)
What is an absolute block section?
The section between Signal Box A’s station limits and Signal Box B’s station limits
OR
The section between the section signal in rear and the home signal controlled ahead
OR
The section between the intermediate block home in rear until the home signal ahead
Who controls absolute block sections?
The signal box ahead as they have to give permission to the previous signal box to allow trains into the absolute block section once the train ahead has been confirmed to have passed the clearance point of 400m beyond the home signal complete with tail lights
Why do trains have to fully pass the clearance point before trains can be allowed into the absolute block section?
To prevent the risk of collision if a train behind were to SPAD the home signal.
What is the purpose of checking for tail lamps?
To confirm that the train hasn’t divided and full train has left the section due to lack of track circuits
If there is only one signal within station limits, what does this signal serve as?
Both the home and section signal
If a distant signal and a stop signal are on the same post, who controls these?
The distant signal is controlled by the signal box ahead and the stop signal is controlled by the signal box at that location
Why would a distant signal and stop signal be placed on the same post?
Where there wouldn’t be service braking distance before the next stop signal.
If you receive an AWS warning before a post with both a distant and a stop signal on, what does this apply to?
The distant signal only but this doesn’t mean that the stop signal is clear.
If there is a junction within station limits, what may there also be?
More than one home signal
Where would these home signals be positioned and how would they work?
One home signal protecting the station on the main line and one home signal protecting the station on the junction- once the train arriving from the main line leaves the station, the signal on the junction can clear
Can there be more than one section signal?
There must only ever be one section signal per line within station limits
What is the purpose of intermediate block sections?
These shorten AB sections to increase capacity
What is the definition of an intermediate block section if there is 1 IB section?
From the section signal in rear to the intermediate block home ahead
What is the definition of an intermediate block section if there are 2 IB sections?
From the IB home in rear to the IB home ahead
Who controls IB sections?
The signal box in rear
How are trains detected in IB sections?
Track circuits
What type of signals are used in IB sections?
Colour light signals only
Are there AWS magnets before IB signals?
Yes, 180m before them.
Do IBH signals have distant signals before them?
Yes.
How would you identify a colour light distant signal?
Triangle or ‘R’ on ID plate.
What are semaphore subsidiary signals?
A subsidiary arm that is associated with the main arm of a stop signal and located below on the same post.
What is meant if the main arm is at danger (horizontal with red light) and the subsidiary arm is horizontal?
Obey the main arm
What is meant if the main arm is at danger and the subsidiary arm is at 45 degrees with green light?
Proceed past the main arm at danger and prepare to stop short of BOTS
What is meant if the main arm is at danger and the subsidiary arm is at 45 degrees with the letter ‘C’?
Calling on- entering a platform permissively- proceed at caution and prepare to stop short of BOTS
What is meant if the main arm is at danger and the subsidiary arm is at 45 degrees with the letter ‘S’?
Shunt ahead- proceed for shunting purposes only (proceed at caution and prepare to stop short of BOTS)
What is meant if the miniature arm is offset from the main signal?
It is a shunting signal- when cleared, proceed at caution and be prepared to stop short of BOTS.
How does semaphore stepped routing work?
Left to right- furthest left signal for the route on the extreme left
Highest step is the highest speed route
Equal steps are equal speed routes
How does semaphore stacked routing work?
Top to bottom, left to right (not based on speed). Top signal applies to furthest left route.
How does semaphore route indicator routing work?
Figure or letter displayed to correspond with the route the move is signalled onto.
If the main arm is at danger, the route indicator is unlit. The arm is the authority to proceed, not the route indicator but both must be correct to proceed.
What are non-block signals?
Signals that do not control the movement of trains- their only purpose is to protect a level crossing and they are controlled by a crossing keeper or signaller.
What would you expect to see if a non-block crossing fails?
A green hand signal as authority to pass over a crossing if the non-block signal protecting the crossing fails. This tells you that the crossing is safe and you have permission to pass the signal at danger.
How do you find out the locations of non-block crossings?
In the Sectional Appendix
What are your actions if a green hand signal is shown at other locations?
Only the crossing is safe but you do not have permission to pass the protecting signal. You must wait for the signal to clear before proceeding.
How are semaphore distant signals replaced?
2 aspect colour lights (yellow/green) with ‘R’ or triangle on ID plate
How are semaphore stop signals replaced?
2 aspect colour lights (Red/green)
When semaphore stop signals are replaced, do they still serve as home and section signals?
Yes
When semaphore signals are replaced with colour lights, does this mean that track circuits are also present?
No
When semaphore stop signals are replaced with colour lights, do they get fitted with AWS magnets?
No, you still won’t receive AWS warnings for stop signals
What is the default position of semaphore signals?
Horizontal until cleared (fail safe)
At what point can distant signals clear?
When all associated stop signals have cleared first
How must you always treat the next stop signal?
Based on what the distant is showing, even if you see the stop signal ahead to be clear.
If you are expecting to work permissively but cannot see another train, what does this mean?
The train has already left and the proceed signal doesn’t apply to you. Wait for the signal to show danger and clear again.
What are your actions if you are unsure of the aspect shown?
Treat as most restrictive and contact signaller.
If the distant signal shows a proceed aspect but you receive an AWS horn, what are your actions?
Treat as cautionary unless the signal clears after passing the AWS magnet or if there is a warning board/emergency indicator positioned at the signal.
What is track circuit block?
The use of track circuits to trace trains and signals that operate with the passing of trains
How are sections in TCB separated?
By insulated block joints to separate sections and set the previous signal to danger when passed.
How do track circuits fail safe?
By displaying a danger aspect.
What is the overlap section?
The portion of line immediately after a signal that must be unoccupied before the next signal in rear can change
What is the overlap in 4 aspect signalling?
200yds overlap
What is the overlap in 3 aspect signalling?
300yds overlap
What is the overlap in 2 aspect signalling?
400yds overlap
How are the aspects controlled in 4 aspect signalling?
IBJ and overlap of 200yds control the aspects
What is the signal section in 4 aspect signalling?
Signal to signal
Where are AWS magnets located in 4 aspect signalling?
Before each signal
How do the aspects change in 4 aspect signalling?
As the trains move through each section, the previous signals change through the sequence, red, single yellow, double yellow, green.
Where is 4 aspect signalling usually located?
Usually on high speed lines with long sections
How are the aspects controlled on 3 aspect signalling?
IBJ and overlap of 300yds
What is the signal section on 3 aspect signalling?
Signal to signal
Where are AWS magnets located on 3 aspect signalling?
AWS magnets before each signal
What is the sequence in 3 aspect signalling?
Green, single yellow, red
What is removed in 3 aspect signalling?
Double yellows
Where is 3 aspect signalling usually located?
On lower speed lines than 4 aspect signalling
How are the aspects controlled in 2 aspect signalling?
Via the IBJ and overlap of 400yds
What is the signal section in 2 aspect signalling?
Stop signal to stop signal
Where are AWS magnets located in 2 aspect signalling?
Before every signal (unlike AB just before distant signals)
What type of signals are utilised in 2 aspect signalling?
Stop (red/green) and distant (yellow/green)
Are home and section signals utilised in 2 aspect signalling?
No, distant and stop signals alternate
How are distant and stop signals arranged?
Distant and stop signals alternate to fit the 2 aspect sequence
When do distant signals turn yellow?
Only when the train passes the IBJ and overlap of the next stop signal.
Do distant signals have an IBJ and overlap?
No - the signal section is stop signal to stop signal.
What is a controlled signal and how would you identify one?
Set and cleared by the signaller. Identified by a black backplate on the ID.
What aspect will be shown on a controlled signal until cleared by the signaller?
Red
Where are controlled signals usually located?
In high risk locations
What are automatic signals and how would you identify one?
Controlled by the passing of trains and may not be able to be overridden or controlled by the signaller. Identified by horizontal black line on white backplate.
What will automatic signals always try to show?
The least restrictive aspect
Where are automatic signals usually located?
In low risk locations
What are junction indicators and where would they be found?
On controlled signals- they show that trains are being signalled to the left or right of a straight route via a line of 5 white lights in 6 possible positions that are read top to bottom (bottom is furthest left or right)
If you are continuing on the straight route, what will the junction indicator show?
No indicator
If there is no obvious straight route, which routes will have junction indicators?
All routes
If there are diverging routes of equal speed, which routes will have junction indicators?
Both routes
Which routes do junction indicators usually apply?
To lower speed routes, even if this is the straight route.
What is an associated position light?
A position light that is positioned below the main aspect on the same post- it is associated with the main aspect.
If the associated position light is unlit, what does this mean?
Obey the main aspect
If the associated position light has 2 whites at 45 degrees with a main aspect showing red, what does this mean?
Proceed past the main aspect at caution and prepare to stop short of BOTS (permissive).
What is a route indicator?
A number or letter corresponding with a route.
If you are entering an intermediate platform, how would the route indicator and main aspect work together?
The aspect shown controls movements onto intermediate platforms whilst the route indicator tells you the platform number.
Eg: (7a, 7b, 7c- if single yellow and number 7, red is at 7a. If green and number 7, red at 7c)
What are outer distant signals and where would they be located?
Usually on high speed lines or before signals with poor sighting- outer distant signals give more notice of an upcoming aspect
How would outer distant signals be denoted on their ID plate?
RR
What aspect would an outer distant show in the signalling sequence?
Double yellow to allow for a single yellow at the distant to follow.
How may the signalling used alternate to allow for an outer distant signal?
May alternate between 4 and 2 aspect to allow for an outer distant.
What are permanent yellows and reds and where might they be found?
At gates/buffers etc as these can never be passed. May have permanent yellow before them to fit the sequence- neither can be cleared.
If transitioning from 3 to 2 aspect, what must the first signal in 2 aspect show?
Either red or green- the first signal must be a stop signal.
If leaving 3 aspect on a green, what must the first signal show in 2 aspect?
Green
If leaving 3 aspect on a single yellow, what must the first signal show in 2 aspect?
Red but could be green
When transitioning from 3 aspect signalling to 4 aspect signalling, what must the first signal in 4 aspect show?
It must fit a 3 aspect sequence
If leaving 3 aspect on a green, what must the first signal in 4 aspect show?
Least restrictive aspect is single yellow- if this clears to green, the following signal could then show a double yellow
When transitioning from 4 to 3 aspect signalling, what could the first signal in 3 aspect signalling show?
Single yellow
What is the risk of transitioning from 4 to 3 aspect signalling?
Lose double yellows- could cause you to approach too quickly if anticipating double yellows.
What is the purpose of flashing yellows?
Confirm the diverging slower speed route is set ahead. These may slow you before the junction even if the junction is clear.
What is a 3 aspect flashing yellow sequence?
Green, Single flashing yellow, steady single yellow before junction, red after junction
What is a 4 aspect flashing yellow sequence?
Green, double flashing yellow, single flashing yellow, steady single yellow before junction, red after junction
What must you always be prepared to do after passing a single steady yellow at a junction?
Be prepared to stop at the red on the junction
What does it mean if the signals are steady when you expect them to be flashing?
Route is not set.
What does it mean if a flashing double yellow is followed by a steady single yellow? What are your actions?
Route no longer set- you will be brought to the junction at danger. Contact signaller as potential for wrong routing
What classifications of trains are there?
Class 0- Light locomotive
Class 1- Express pax
Class 2- Stopping pax
Class 3- ECS specially advised
Class 5- ECS train
What is permissive working?
Where more than one train is signalled onto an occupied line
What classification of train can you work permissively with?
0, 1, 2, 3 & 5
What must you do if asked to work permissively at an unusual location?
Always ask the signaller what you are working permissively with
At what locations is permissive working permitted?
At locations specified in the Sectional Appendix
How must you proceed when working permissively?
At caution and being prepared to stop short of BOTS.
In pax service, how are you signalled?
Signalled to final destination (eg: platform)- main aspect with associated position light
If ECS, how are you signalled?
Position light to position light as lower priority
Can class 1 and 2 trains enter goods loops?
Only with permission
Can class 1 and 2 trains enter pax loops?
Yes
Can class 3 & 5 trains enter goods loops?
Yes- they can work permissively with freight
What does it mean if you are entering a goods loop via main aspect with an unlit position light?
No one else is in the loop
What must you leave a station under the authority of?
A main aspect- must never leave on authority of a position light
In what circumstances can you leave the station under authority of a position light?
Shunting- working position light to position light
If you are ECS to another location via main line, can you leave on authority of a position light?
No, you must still receive a main aspect to depart the station.
Where might position lights that aren’t associated with a main aspect be located?
At ground level or on a stick
When you are proceeding on the authority of a main aspect, what will happen to any GPLs along the route?
These will clear
What may GPLs contain to confirm which line they apply to?
Arrows
What does a GPL showing stop/danger look like?
2 horizontal reds or 1 red and 1 white light horizontal
What does a yellow GPL showing stop/danger look like and what is the difference between this and a red GPL?
2 horizontal yellows or 1 yellow and 1 white horizontal. Yellow GPLs can be passed if showing danger if proceeding for shunting purposes but not making movement towards main line.
If making movement towards main line, you must stop.
What does a GPL showing 2 whites at 45 degrees mean?
Authority to proceed at caution and be prepared to stop short of BOTS
What does a GPL associated with a route indicator confirm?
Confirms the route the movement is signalled onto.
How would you know that a colour light signal is not in use?
Black bag with white X on it.
