scope:

Requirements in this module apply to layouts when infrastructure layout changes take place:

a)  resignalling;

NOTE 1  Whilst a relock or recontrol would be unlikely to provide the opportunity to change the physical track layout, it might be practicable to implement updated controls or enable the removal of trapping protection which is no longer justified.

b)  alterations are made to an existing layout;

c)  renewals of infrastructure where there are points or derailers that provide trapping protection;

d)  the designated purposeof lines and sidings are changed including:

•    when changes are made to the use of reception lines, sidings and adjacent facilities, especially at the boundary with other administrations

•    when the change of use relates to the stabling of trains.

This module does not cover points provided on a running line to derail a portion of a divided train on a falling gradient (run back catch points).

NOTE 2: Such points should not be retained because these points stem from a time of loose coupled freight trains where the risk from dividing was materially larger; fully fitted trains are designed to arrest themselves. Where gradient is particularly steep the higher consequence or perceived risk could warrant their consideration.

NOTE 3: The term trap points does include a set of points provided at the entrance to a loop or goods line to protect a running line where unattended vehicles could roll out onto the line (often called worked catch points).

Where trap points form a part of an overlap the requirements of NR/L2/SIG/30009/A450 and D450 additionally apply.

Purpose

This module forms part of the Signalling Principles Handbook (NR/L2/SIG/30009) and is to be read in conjunction with the other sections of the handbook.

It describes appropriate measures of trapping protection to control the consequences of vehicles running away and of signal overrun from non-signalled movements.