Absolute Block Signalling Flashcards
Draw the main features of ABS.
What is absolute block signalling?
A method that allows only one train in a block section at a time
What is a block section?
A section of track between two signal boxes under the control of absolute block signalling
When can a train enter a block section under absolute block rules?
Only when the section is confirmed clear by the next signal box
What ensures a block section is clear before a train enters?
Communication between signallers using block instruments and bell codes
What is the purpose of absolute block signalling?
To prevent more than one train being in the same section, ensuring safety
Who authorises a train to enter a block section?
The signaller at the rear, after receiving clearance from the forward signal box
What must happen before a signaller can offer a train forward?
They must ensure the line is clear up to the section signal
What does the term ‘line clear’ mean?
Confirmation from the next signal box that the block section is clear for a train to enter
Can absolute block be used during degraded working?
No – other forms of signalling or procedures (e.g., pilotman working) are used instead
What type of lines typically use absolute block?
Conventional lines controlled by signal boxes with mechanical or traditional signalling systems
