scope:

This instruction applies to all buffer stops which are designed to be displaced in the event of impact and which are on or adjacent to passenger lines.

Purpose of TI

An energy absorbing buffer stop (often known as a friction or sliding buffer stop) is only fully effective when the buffer stop is in its designed position. If it has been displaced along the line (past the point defined by the track engineer) then it may retard a train too rapidly (putting passengers at risk) or fail to stop the train in the available distance.

A track circuit interrupter (TCI), or other detector, shall be provided to detect that a friction buffer stop has not been moved past the point at which it remains effective.

This instruction details the minimum controls to be applied where it is detected that a buffer stop has been displaced beyond the critical point and provides an update to NR/SP/SIG/11752 pending its update.