Signalling Flashcards
What is the main principle of Absolute Block Signalling?
Ensuring that there is only ever one train in one section at any one time. This is to keep trains apart and prevent collisions.
What are the limitations of absolute block signalling?
Long sections covered by absolute block which can make it difficult to increase capacity on these lines.
What type of signals are relied upon within absolute block signalling?
Semaphore signals mainly but colour light aspects can also be used in sections of intermediate block signalling.
How can you identify that a semaphore signal applies to you?
It should be red and white or yellow and black when facing the signal (not black and white as this is the colour of the back of the signal and will apply to trains on the opposite line). Signals that apply to you should also be pointing left with the signal post on the right.
What is meant by a red and white semaphore signal that is in the horizontal position or featuring a red light at night?
Signal at danger/ stop.
What is meant by a red and white semaphore signal that is tilted at 45 degrees and features a green light at night?
Proceed.
Which signals within absolute block signaling will you also receive an AWS signal with?
Just distant signals, not stop signals. You will receive AWS warnings for both distant and stop signals within an intermediate block section.
How far in advance of a distant signal will you receive an AWS warning?
180 metres before the distant signal.
What is the purpose of a backing plate behind a semaphore signal?
To make the signal clearer.
What are distant signals?
Signals that cannot show a stop/danger aspect or indication.
What is meant by a black and yellow semaphore signal that has the arm in the horizontal position and features a yellow night at light?
Proceed at caution. Be prepared to stop at the next stop signal or other specified place to which the distant signal applies. Any associated stop signals that are controlled by the same signal box will be displaying a danger aspect.
What is meant by a black and yellow semaphore signal where the arm is raised or lowered 45 degrees and a green light is displayed at night?
All associated stop signals worked by the same signal box will be clear (displaying a proceed aspect).
How far from stop signals are distant signals placed?
Within service braking distance.
What is service braking distance?
This is calculated based on line speed and the worst performing train’s braking ability.
What should your actions be as a driver who has received a cautionary distant signal but upon approaching the stop signal the danger aspect changes to a proceed aspect?
You may proceed past this signal but you must be prepared to stop at the next stop signal that is controlled by the same signal box.
In an area that a signal box controls, what is the name of the first signal?
The home signal.
In an area that a signaller controls, what is the final signal before leaving that area called?
The Section Signal.
What is the section between the home signal and the section signal referred to as?
Station limits.
Can stations be included within a signaller’s station limits?
Yes but they don’t have to contain a station.
What is the area between Signal Box A’s Section Signal and Signal Box B’s Home Signal called?
The Absolute Block Section.
Who needs to give permission for a train to move into the Absolute Block Section and why?
Signal Box A must seek the permission of Signal Box B for a train to move into the Absolute Block Section. Whilst Signal box B doesn’t control the Absolute Block Section, they will be able to visually see whether the train in front has left the absolute block section and passed the clearance point.
When a train passes the home signal, what is the signaller looking to determine? How does he do this?
Whether the train is fully within his station limits. He does by looking for taillights once the train has passed the Clearance Point.
What is the clearance point?
400m or 1/4 of a mile past the home signal.
Why does the signaller look for taillights?
To see that the train has fully left the section prior to his station limits. If there are no visible taillights, the train could have separated and part of it could be in the previous section.
How might the clearance point be used to prevent SPADs?
When a train is approaching the home signal, there may already be a train within that signaller’s station limits. The signaller can use the clearance point to determine that the train in front is definitely out of the way, in the event that the train behind passes the home signal at danger. This prevents collision.
When a signaller only has one stop signal within his station limits, is this considered to be the home signal or the section signal?
It is considered to be both.
Where there is only one stop signal within a signaller’s station limits that is considered to be both the home and the section signal, what would you expect to see before it?
A distant signal with AWS magnet to tell you whether this stop signal is displaying a danger or a proceed aspect.
If a danger aspect is initially showing on a single stop signal that then changes to a proceed aspect what does this tell you in terms of the signal itself and what are your actions as the driver?
When the single stop signal is initially showing a danger aspect, it is considered to be the home signal and you must stop at this. When this changes to a proceed aspect, the stop signal then becomes the section signal and you may pass the signal to leave that signaller’s station limits and enter the absolute block section.
What does it mean if a distant signal is on the same post as a stop signal?
The stop signal is worked by the signal box at that location and the distant signal is worked by the signal box ahead.
Why might a distant signal that applies to a stop signal ahead be located on the same post as the previous stop signal?
Because there is no service braking distance for the next stop signal so this is the only suitable location for the distant signal.
What does it mean if the stop signal is at danger (horizontal) and the distant signal is at caution (horizontal) on the same post?
You must obey the most restrictive aspect and stop at this signal. The stop signal ahead (and any associated signals) will also be showing a danger aspect.
What does it mean if the stop signal is at proceed (45 degrees) and the distant signal is at caution (horizontal) on the same post?
You may proceed past this signal but the stop signal ahead (and all associated signals) will be showing a danger aspect.
What does it mean if the stop signal is at proceed (45 degrees) and the distant signal is also at proceed (45 degrees) on the same post?
You may proceed past this signal and the stop signal ahead (and any associated signals) will be showing a proceed aspect.
What does a white diamond denote on a signal post?
That area is track circuited and the signaller knows of your presence even though he cannot see you from his signal box.
How long must you wait before contacting the signaller when stopped at a signal post displaying a white diamond?
Up to 10 minutes.
Where there are a number of junctions in and out of a signaller’s station limits, how many home signals can there be and how many section signals can there be?
There is no limit to the number of home sections that can exist within a signaller’s station limits but there can only be one section signal in the direction of travel to signify the end of the station limits (one per line if two or more running lines).
Explain how the home signals would work to allow one train from a running line into a station within the signaller’s station limits whilst holding another train, joining from a junction, outside of the station?
The home signal on the main line would allow a train into the station. A separate home signal would then hold another train joining from a junction and prevent them from coming into the station as there is already a train within that section (one train in one section at one time).
What is the definition of an Intermediate Block Section?
The area from the section signal in rear until the intermediate block home ahead (where there is one intermediate block section) or the area from the intermediate block home in rear until the intermediate block home ahead (where there is more than one intermediate block section).
What is the purpose of Intermediate Block Sections?
As some areas of absolute block can be particularly lengthy, intermediate block sections allow for these to be shortened to allow more trains over this portion of line but whilst adhering to the principle of ‘one train in one section at one time’. This allows for greater capacity on these lines.
How are Intermediate Block Sections controlled?
These sections are track circuited and are controlled by the previous signal box.
What type of signals exist within intermediate block sections?
Colour light signals.
Do intermediate block signals and any associated distant signals contain AWS magnets and would you receive any cab warnings for these?
Yes, both intermediate block home signals and associated distant signals will contain AWS magnets unlike signals within normal absolute block signalling where only the distant signals are fitted with AWS. As such, you will receive cab warnings for both intermediate block home signals and associated distant signals.
For any type of distant signal, how far in advance of the signal would the AWS magnet be located?
180 metres
Describe the signal post sign that denotes a signal is an intermediate block signal?
White background with black vertical line.
What signal post sign would be located on a distant signal within an intermediate block section?
A triangle symbol or the letter ‘R’ to denote that it is a distant signal.
Where an intermediate block section exists, what does this change the definition of an absolute block section to?
The section between the intermediate block home in rear to the home signal ahead.
What is a semaphore subsidiary signal?
Semaphore subsidiary signals are always associated with the main arm of the semaphore stop signal and will always be located below the main arm on the same post.
What is meant when the subsidiary arm is in the horizontal position or a red, white or no light is showing?
Obey the main arm.
What is meant when the subsidiary arm is at 45 degrees or a green light is shown?
This should be read as a proceed aspect and authorises the driver to pass the main arm at danger and proceed at caution towards the next train, signal or buffer stop and to be prepared to stop short of any obstruction.
What is meant by a subsidiary arm that is displaying the letter C?
Calling On. This authorises the driver to pass the main arm at danger and proceed at caution towards the next train, signal or buffer stop and be prepared to stop short of any obstruction (likely to mean that you are calling at a station where a train is already at a stand and you will be entering permissively).
What is meant by a subsidiary arm that is displaying the letter S?
Shunt Ahead. This authorises the driver to pass the main arm at danger and proceed at caution for shunting purposes only.
What does a miniature arm offset from the main signal tell you?
This is a shunting signal and not a subsidiary arm.
What is permissive working and give an example of where this might be done on a day-to-day basis?
Where more than one train is allowed into a section at any one time. Pulling into a station where a train is already at a stand is an example of permissive working.
Name the three ways in which routing can be done with semaphore signals?
Stepped, stacked and route indicator
What is stepped routing in semaphore signalled areas?
The highest step denotes the highest speed route. The lowest step denotes the lowest speed route. If two steps are the same height, these individual routes will share the same speed. The signals will also be ordered from left to right to help drivers identify which route is theirs (the first signal on the left will apply to the furthest left route).
What is stacked routing in semaphore signalled areas?
Displays signals from top to bottom on the signal post and this corresponds the running lines from left to right (the top signal applies to the furthest left route).
How is a route indicator used to route trains in semaphore signalled areas?
A figure or letter will be shown on the signal itself which will contain a semaphore arm to show which route the movement is being signalled onto. When the signal is at danger, the route indicator will be unlit. When the signal is cleared, the route indicator will illuminate.
What are your actions as a driver if the route indicator becomes lit but the signal arm remains at danger?
You do not have authority to proceed. You must wait for the signal arm to clear. The signal arm should ways be your indication to proceed, not the route indicator.
What does an illuminated route indicator tell you about the points for the route you are about to take?
These are all set correctly.
If the semaphore arm clears but you do not receive an illuminated route indicator, what are your actions and why?
Do not proceed and contact the signaller. The points for your route may not be set.
What is a non-block signal?
Non-block signals aren’t used for the usual purpose of signals within absolute block signalling to keep trains apart or control movements and aren’t constricted to absolute block rules (one train, one section, one time). However, non-block signals could be in place to protect something else such as a level crossing.
Who would normally control a level crossing that falls within a signal box’s station limits?
Could be controlled by that signal box but is more likely controlled by a separate crossing keeper.
What might you expect to see if a non-block signal fails at a level crossing, where this signal purely protects the level crossing, and what would your actions be as a driver?
You may receive a green hand signal (green flag is waved) from the Crossing Keeper to tell you that the crossing is clear.
Where can drivers find the locations where a green hand signal/flag may be shown in the event of a non-block signal failure?
The Sectional Appendix.
What are your actions if you receive a green flag at a level crossing that is not listed in the Sectional Appendix as an area where a green flag can be shown in the event of a non-block signal failure and where that signal is a normal block signal?
You must ensure that you have a proceed aspect on the applicable signal before proceeding over the signal as the green hand signal does not replace the normal block signal that falls before the level crossing. If you pass a signal due to receiving a green flag when the signal itself is not clear, this would be considered as a SPAD.
When the railway is updated, how might a semaphore distant signal be replaced?
With a 2 aspect colour light head that can show either a green or yellow aspect. The signal ID plate would still contain a triangle or the letter ‘R’ to denote that it is a distant signal.
When the railway is updated, how might a semaphore stop signal be replaced?
With a 2 aspect colour light head that can show either a red or green aspect. These can still be either a home or a section signal.
Is it possible for absolute block signalled areas to contain colour light signals and semaphore signals?
Yes.
Where there are colour light signals in an absolute block signalled area, does this mean that the section is track circuited?
No.
Do colour light stop signals receive AWS warnings?
No, you would only receive AWS warnings for distant signals irrespective of whether they are semaphore or colour light. The only time you would get AWS warnings for both stop and distant signals is in an intermediate block section.
What is the normal position for a semaphore stop signal and why?
The normal position for a semaphore stop signal is always horizontal/danger until it is cleared. If this signal fails, it will always fail safe in the horizontal position.
How can distant signals be cleared?
Distant signals cannot clear until all associated stop signals are cleared. This means that if all the stop signals are at danger, the distant cannot clear until all stop signals have changed to a proceed aspect. Therefore, the distant will always be the last to clear.
If you are acting permissively and you are signalled to ‘call on’ and expect to see another train but do not, and the signal ahead is displaying a proceed aspect. What must your actions be as a driver?
Do not assume that the proceed aspect is for you. The train that you were going to be acting permissively with has most likely already left and the signal was for them but this signal has not cleared yet. You must wait for the signal to display a danger aspect and then wait for it to clear again before proceeding.
