Independent Safety Assessment -- The IEE/BCS Independent Safety Assurance Working Group -- Putting Trust into Safety Arguments -- Independent Safety Assessment of Safety Arguments -- Safety and Security -- Structuring a Safety Case for an Air Traffic Control Operations Room -- SafSec: Commonalities Between Safety and Security Assurance -- Accident Investigation -- Learning from a Train Derailment -- Accident Investigations - Meeting the challenge of new technology -- Risk and its Tolerability -- Identification of Time At Risk Periods of Significance to ALARP Justifications -- Developing and Using Risk Matrices -- Achieving and Arguing the Safety of Modular Systems -- Health Monitoring for Reconfigurable Integrated Control Systems -- Exploring the Possibilities Towards a Preliminary Safety Case for IMA Blueprints -- Modular Certification of Integrated Modular Systems -- Technologies for Dependability -- The Effects of Timing and Collaboration on Dependability in the Neonatal Intensive Care Unit -- Applying Java™ Technologies to Mission-Critical and Safety-Critical Development.Constituents of Modern System-safety Thinking contains the invited papers presented at the Thirteenth annual Safety-critical Systems Symposium, held at Southampton, UK in February 2005. The papers included in this volume bring together topics that are of the utmost importance in current safety thinking. The core of modern safety thinking and practice is a risk-based approach, and, this is not only a common thread running throughout the papers, but is also explored in two of them. Other themes considered include the safety case, safety assessment, accident investigation, and the commonality between the processes and techniques employed in safety and security engineering. Papers contain extensive industrial experience as well as recent academic research and are presented under the headings: Independent Safety Assessment, Safety and Security, Accident Investigation, Risk and its Tolerability, Achieving and Arguing the Safety of Modular Systems, and Technologies for Dependability.