Where trains are worked on the Absolute Block System only one train at a time shall be allowed to occupy the block section between the adjoining two block stations, and to ensure that;
(a) No train shall be allowed to leave a block station unless Line Clear has been received from the block station in advance, and
(b) On double lines, such Line Clear shall not be given unless the line is clear of trains running in the same direction not only up to the first Stop signal at the block station granting Line Clear but also for an adequate distance of not less than one hundred eighty meters beyond it;
(c) On single line, such Line Clear shall not be given unless the line is clear of trains running in the same direction, not only up to the first Stop signal at the block station granting Line Clear but also for an adequate distance of not less than one hundred eighty meters beyond it, and is also clear of trains running in the direction towards the block station to which such line clear is given.
B - Conditions for granting Line Clear and obstruction at class 'B' Station on double line