This document provides requirements and guidance of the Independent Safety Assessor for Railway Systems Accreditation Sub-program that SCC operates and is a companion to ISO/IEC 17020. It outlines unique Canadian requirements of the SCC Accreditation Sub-program for Independent Safety Assessors (ISAs) that carry out independent safety assessments of the suitability and application of both the risk management process and its results for changes to a Railway System, and that carry out independent assessments of system assurance processes for a Railway System.