Book excerpt: System safety is the application of engineering and management principles, criteria, and techniques to optimize safety within the constraints of operational effectiveness, time, and cost throughout all phases of the system life cycle. System safety is to safety as systems engineering is to engineering. When performing appropriate analysis, the evaluation is performed holistically by tying into systems engineering practices and ensuring that system safety has an integrated system-level perspective.The NASA System Safety Handbook presents the overall framework for System Safety and provides the general concepts needed to implement the framework. The treatment addresses activities throughout the system life cycle to assure that the system meets safety performance requirements and is as safe as reasonably practicable.This handbook is intended for project management and engineering teams and for those with review and oversight responsibilities. It can be used both in a forward-thinking mode to promote the development of safe systems, and in a retrospective mode to determine whether desired safety objectives have been achieved.The topics covered in this volume include general approaches for formulating a hierarchy of safety objectives, generating a corresponding hierarchical set of safety claims, characterizing the system safety activities needed to provide supporting evidence, and presenting a risk-informed safety case that validates the claims. Volume 2, to be completed in 2012, will provide specific guidance on the conduct of the major system safety activities and the development of the evidence.