NR NR/L2/SIG/11201/MOD B7 ISSUE 9 PDF

Signalling Systems (Types)

This module provides application guidance to the design of interlockings (including ground frames) to meet NR/L2/SIG/30009/(all modules) Interlocking Principles through the following:

a) mechanical signalling systems (see also NR/L2/SIG/11201, Module B8);

b) electro-mechanical signalling systems;

c) electro-pneumatic signalling systems;

d) all-electric non-route setting signalling systems;

e) free-wired route setting signalling systems (see also applications in NR/L2/SIG/11201, Module B9);

f) geographical route setting signalling systems (see also NR/L2/SIG/11201, Module B10); 

g) electronic signalling systems [see also NR/L2/SIG/11201, Module B11 and for GB Solid State Interlockings NR/L2/SIG/17002 and SSI8003]. 

Hybrid combinations of the above systems are likely to require a ‘per site’ justification of the safety architecture. 

NOTE: Where appropriate, reference to “signals and routes” should be understood to apply to movement authorities within cab signalling systems whether or not lineside signals are also provided. 

The examples shown in this Standard are based on the signalling layout and control table illustrations given in NR/L2/SIG/11201, Module A5-3. 

Presentation and Production Processes 

This module does not cover the presentation and production processes for design details. For the presentation and use of mechanical locking charts, interlocking circuit diagrams and central interlocking data listings within the design process, see NR/L2/SIG/11201, Module A4-1 to 4-8 and NR/L2/SIG/11201, Module A5-2. Documentary requirements for control tables are given in NR/L2/SIG/11201, Module A5-3. 

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. 

This Network Rail standard contains requirements and general guidance on signalling engineering applications. The content supports the specific and general requirements described in Railway Group Standards and Railway Industry Standards. Additionally, it records the approach of legacy installations where thecurrent Network Rail Signalling Principles Handbook [NR/L2/SIG/30009] is not universally applicable. 

NOTE: 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 30009 shall take precedence, subject to the provisions required for consistency, described in this introduction. 

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

NOTE: Use of designer notes on drawings (also known as Y-Notes, also 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. 

Consistency 

Where greenfield new works abut existing installations, it is important to consider whether the use of best practice current principles would either be confusing or incompatible with the existing practice at the adjacent installation. This 11201 module has sections which describe historic network-wide practice. It should not be presumed that adoption of the latest principles should supersede or replace the existing application design; this has to be a reasoned judgment which, for each project, is recorded in the Reasonable Opportunity assessment, see NR/L2/SIG/ 30009/E810. The boundaries between, and overlapping of, differing practices within installations and at their boundaries, including during staged/phased change, should be chosen to provide justifiably safe and economically viable compromises.