scope:

This module describes the parameters to be considered in the design or selection of geographical relay interlocking systems.

NR/L2/SIG/11201, Module B7, Section 3 laid down the requirements for interlocking controls and specified their tabulation in control tables. The application of the principles and requirements to route setting systems are summarised in

NR/L2/SIG/11201, Module B7, Section 7. This module demonstrates how those controls may be provided by the use of geographical relay systems. Figures 1 to 6 identify how the standard controls are applied to some common geographical interlockings and enable a comparison with the other interlocking systems.

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 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 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 shall not take precedence

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

NOTE 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.