scope:

The contents of this module supports RSSB documents GK/RT0055 and GK/GN0655 and applies to all single lines and bi-directional lines where trains are controlled in accordance with the following methods:

• Absolute Block, Interlocked System;

• Tokenless Block System;

• Electric Token Systems;

• No-Signaller Token, Remote System;

• One-train Staff System;

• One-train System Without Staff.

The following methods of control are excluded and are the subject of other NR/L2/SIG/30009 modules and Railway Group Standards:

• Track Circuit Block, with and without additional directional or acceptance controls;

• Radio Electronic Token Block (refer to GK/GN0554 Iss 2; this Railway Group Standard does not reflect changes made to RETB since 2013);

• Staff and Ticket working (these installations are subject to an individually determined specification to suit local requirements).

For comparative purposes they are however included in Table B1 - Tabulation of Key Features.

This module applies to all new provision and, subject to consideration of "using reasonable opportunity" and practicability, all alterations to signalling where the changes appreciably alter the layout risk associated with any of the signals within the scheme. Where the content of application standards (such as NR/L2/SIG/11201, SSI8003, CAT0005) are different to the requirements described in this module, this module takes precedence.

Changes to layout risk are likely when any of the following apply:

a) alterations are made to a layout;

b) lines or sidings become designated as passenger lines;

c) layouts are re-signalled or relocked (or re-controlled, though it is recognised that the opportunity to mitigate existing risk is generally limited);

d) additional routes are provided;

e) a platform is added;

f) permissible or attainable speeds are changed, raised or lowered;

g) an overrun or timetable risk assessment (or similar) identifies the need to review protection.

It is not intended to be applied to minor signalling alterations where the scope of the scheme does not make any material impact to layout risk on any of the signals within the scheme.

Purpose

The purpose of this module is to define the signalling requirements for the safe movement of trains on single lines and equivalent bi-directional lines.

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

It details Network Rail's requirements for the provision of block controls and interlocking between signals, movable infrastructure such as points and other parts of the signalling system to control the risk of:

a) failure of moving infrastructure to establish a wheeled path;

b) collision between a train and another train legitimately present;

c) the issuing of a movement authority to the train driver and its subsequent removal.

This module comprises mandatory sections and guidance. The guidance is to be followed unless an alternative can be demonstrated to be beneficial and no less safe.

It satisfies the relevant parts of the IRSE Fundamental Requirements for Train Control Systems, see Appendix 1 for extract.