Track Circuit Block Flashcards
(28 cards)
What is Track Circuit Block Signalling
Track Circuit Block Signalling is the main type of Signalling found on the Northern Network. It is separated into Block Sections by Insulated Block Joints (IBJs) and the signals are colour light signals.
What is the principle of Track Circuit Block Signalling?
One train, in one SIGNAL section, at one time.
What is an aspect and how many aspects can a colour light signal have?
An aspect is a colour light. You can find single, or 2, 3 and 4 aspect signals across the Northern network.
What does a green aspect mean?
Proceed: be prepared to find the next signal at proceed.
What does a double yellow aspect mean?
Preliminary Caution: be prepared to find the next signal displaying a single yellow aspect.
What does a single yellow aspect mean?
Caution: Be prepared to stop at the next signal.
What does a red aspect mean?
Danger. Stop.
What is an IBJ?
An insulated block joint. Signal sections are separated by IBJs as low voltage runs between each section.
Once a train enters that signal section, the circuit is broken, the presence of a train is known so the signal at the rear reverts to danger.
What is overlap after a signal?
After a train has passed a signal and entered that section, the signal reverts to danger. However, the signal before that will still be on danger until the train passes the overlap. The overlap distance depends on how many aspects the signal may have.
2 aspect or AB: 440 yards
3 aspect: 300 yards
4 aspect: 200 yards
What is an OFF indicator?
Conductors must have clear sight of the signal they are dispatching against. In locations where sight is difficult, an off indicator may be present.
They will be positioned where it is clear for the conductor to see during dispatch.
If the OFF indicator is illuminated, it means the corresponding signal is at proceed. If it is NOT illuminated, the signal will be at DANGER.
What is a Co-Acting Signal?
A co-acting signal is a duplicate signal and is used where the main signal is obscured. It enables the conductor to carry out dispatch duties safely. It can be found in the ground or positioned above / opposite side of the track.
What is a banner repeater signal?
A banner repeater signal is found trackside or on platforms and indicates the signal associated with the banner repeater is obscured - so the banner repeater gives advance notice of what the signal is showing. There are 2-state and 3-state banner repeaters.
What is a SPAD Indicator?
SPAD indicators are placed at high-risk SPAD locations e.g entrance to a single line, at a junction or main stations. They are blue-bordered and usually placed 50m beyond the signal they are associated with.
What aspects show if a SPAD Indicator has been activated?
The top and bottom aspects show flashing red, and the middle aspect stays a steady red with the word STOP inside.
Position Light Signals - what are they?
Position light signals are the triangle shaped position lights independent of a main aspect. They are normally used for shunt movements.
What lights would come on a Red Aspect Position Light Signal at Danger?
Two red OR One red, One white in Horizontal Postion
What lights would come on a Red Aspect Position Light Signal at Proceed?
Two White lights at 45 degrees - proceed at caution to the next signal and be prepared to stop short of any obstruction.
What do Yellow Aspects mean on Position Light Signals?
2 yellow or 1 yellow, 1 white horizontal: Danger - Stop HOWEVER you may proceed at caution if the movement is being made toward the shunt neck or siding and not the running line
2 white lights - proceed at caution to the running line.
Position Lights can also be found under main aspects with which type of working / platforms?
Permissive working / Permissive Platforms.
If position light unlit, obey main signal. If two white lights at 45 degrees, proceed at caution.
Limit of Shunt signals - what are they and how do you draw them?
Limit of Shunt Signals - they are another type of stop signal during shunt movements. Drivers use these to determine how far they may shunt their train. If a train passes a shunt signal or indicator, this is classed as a SPAD.
Limit of Shunt - Red writing, circle white background
Shunt Limit - Red Writing, Square Background
Position Light with two red lights horizontally - also known as devil eyes
Junction Indicators: What are they?
Junction Indicators show a train is being signalled either to the left or right of the straight route. A junction indicator will display a line of 5 WHITE Lunar Lights when a proceed aspect is displayed.
If a junction indicator is showing less than 3 lunar lights, what is this known as?
A signal irregularity.
What are the position numbers for multiple junction indicators, and how many could you find on a single signal? Draw if possible.
1,2,3 on the left going down, 4,5,6 on the right going down. You can have a maximum of 6 junction indicators on a single signal.
Flashing Yellow Aspects on a Main Aspect - what do they mean?
Flashing yellow aspects are used to warn drivers they are approaching a diverging junction where the speed of the train MUST be reduced.
The sequence goes Green - Flashing double yellow - Flashing single yellow - Single Yellow Steady with Junction Indicator.
