The safety case (SC) is one of the railway industry's most important deliverables for creating confidence in their systems. This is the first book on how to write an SC, based on the standard EN 50129:2003. Experience has shown that preparing and understanding an SC is difficult and time consuming, and as such the book provides insights that enhance the training for writing an SC. The book discusses both "regular" safety cases and agile safety cases, which avoid too much documentation, improve communication between the stakeholders, allow quicker approval of the system, and which are important in the light of rapidly changing technology. In addition, it discusses the necessity of frequently updating software due to market requirements, changes in requirements and increased cyber-security threats. After a general introduction to SCs and agile thinking in chapter 1, chapter 2 describes the majority of the roles that are relevant when developing railway-signaling systems. Next, chapter 3 provides information related to the assessment of signaling systems, to certifications based on IEC 61508 and to the authorization of signaling systems. Chapter 4 then explains how an agile safety plan satisfying the requirements given in EN 50126-1:1999 can be developed, while chapter 5 provides a brief introduction to safety case patterns and notations. Lastly, chapter 6 combines all this and describes how an (agile) SC can be developed and what it should include. To ensure that infrastructure managers, suppliers, consultants and others can take full advantage of the agile mind-set, the book includes concrete examples and presents relevant agile practices. Although the scope of the book is limited to signaling systems, the basic foundations for (agile) SCs are clearly described so that they can also be applied in other cases.

This book aims to facilitate and improve development work related to all documents and information required by functional safety standards. Proof of Compliance (PoC) is important for the assessor and certification bodies when called up to confirm that the manufacturer has developed a software system according to the required safety standards. While PoC documents add functionality to the product neither for the developer nor for the customer, they do add confidence and trust to the product and ease certification, and as such are important for the product's value. In spite of this added value, the documentation needed for PoC is often developed late in the project and in a haphazard manner. This book aims at developers, assessors, certification bodies, and purchasers of safety instrumented systems and informs the reader about the most important PoC documents. A typical PoC documentation encompasses 50 to 200 documents, several of which are named in the safety standards (e.g., 82 documents in IEC 61508:2010 series, 101 documents in EN 5012X series and 106 work products in ISO 26262:2018 series). These documents also include further references, typically one to twenty of them, and the total number of pages developed by the manufacturer varies between 2000 and 10000 pages. The book provides guidance and examples what to include in the relevant plans and documents.

This book addresses the development of safety-critical software and to this end proposes the SafeScrum (R) methodology. SafeScrum (R) was inspired by the agile method Scrum, which is extensively used in many areas of the software industry. Scrum is, however, not intended or designed for use with safety-critical systems; hence the authors propose guidelines and additions to make it both practically useful and compliant with the additional requirements found in safety standards. The book provides an overview of agile software development and how it can be linked to safety and relevant safety standards. SafeScrum (R) is described in detail as a useful approach for reaping the benefits of agile methods, and is intended as a set of ideas and a basis for adaptation in industry projects. The book covers roles, processes and practices, and documentation. It also includes tips on how standard software process tools can be employed. Lastly, some insights into relevant research in this new and emerging field are provided, and selected real-world examples are presented. The ideas and descriptions in this book are based on collaboration with the industry, in the form of discussions with assessment organizations, general discussions within the research fields of safety and software, and last but not least, the authors' own experiences and ideas. It was mainly written for practitioners in industry who know a great deal about how to produce safety-critical software but less about agile development in general and Scrum in particular.

The safety case (SC) is one of the railway industry's most important deliverables for creating confidence in their systems. This is the first book on how to write an SC, based on the standard EN 50129:2003. Experience has shown that preparing and understanding an SC is difficult and time consuming, and as such the book provides insights that enhance the training for writing an SC. The book discusses both "regular" safety cases and agile safety cases, which avoid too much documentation, improve communication between the stakeholders, allow quicker approval of the system, and which are important in the light of rapidly changing technology. In addition, it discusses the necessity of frequently updating software due to market requirements, changes in requirements and increased cyber-security threats. After a general introduction to SCs and agile thinking in chapter 1, chapter 2 describes the majority of the roles that are relevant when developing railway-signaling systems. Next, chapter 3 provides information related to the assessment of signaling systems, to certifications based on IEC 61508 and to the authorization of signaling systems. Chapter 4 then explains how an agile safety plan satisfying the requirements given in EN 50126-1:1999 can be developed, while chapter 5 provides a brief introduction to safety case patterns and notations. Lastly, chapter 6 combines all this and describes how an (agile) SC can be developed and what it should include. To ensure that infrastructure managers, suppliers, consultants and others can take full advantage of the agile mind-set, the book includes concrete examples and presents relevant agile practices. Although the scope of the book is limited to signaling systems, the basic foundations for (agile) SCs are clearly described so that they can also be applied in other cases.