scope:

This module details the action to be undertaken when undertaking detailed design at existing signalling installations. When alterations are undertaken on existing signalling installations, the infrastructure controller should consider whether certain retrospective safety work should be carried out: both on the parts of the installation being altered and on those parts directly associated with the installation being altered.

Purpose and Introduction

This module forms part of the Signalling Design handbook (SDH: NR/L2/SIG/11201) and is to be read in conjunction with the other modules of the handbook and reference documentation

It contains requirements and guidance on signalling engineering applications. The content supports the specific and general requirements described in Railway Group Standards and the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009].

NOTE 1: Where there is a conflict between this standard and a Railway Group Standard or the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009] then this standard does not take precedence

Decisions made by a competent person should be supported by appropriate evidence or documentation.

NOTE 2: Use of designer notes on drawings (see HSE CDM guidance) will generally suffice as may Design Log entries.

Any adoption of alternative solutions requires an assessment commensurate with the significance of the proposed change and which follows the guidance provided by the Common Safety Method for Risk Evaluation and Assessment [CSM-RA]; Network Rail's adopted method for the control of safety risks.