scope:

The requirements of this Code of Practice apply to electro-mechanical relays that form part of the infrastructure based railway signalling control system, and which are used in safetycritical or safety-related applications.

Risk assessment results for specific interlocking types are recorded in Codes of Practice. Further risk assessment results may be issued as Codes of Practice upon demonstration of requirement and robust assessment.

Purpose

This Code of Practice defines a process to assess the risks presented by failure of specific applications of signalling control relays. By applying the process it is possible to determine which relays (if any) may be exempt from routine replacement for a specific interlocking design.