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