ASCAD Manual

The Adelard Safety Case Development (ASCAD) Manual

In support of the safety community Adelard has decided to make the manual publicly available.

While now available free of charge to individuals, copyright is retained by Adelard. Conditions of use are:

  • The manual may only be used by the individual who downloads the document. It may not be passed on to anyone else without permission from Adelard. Other interested parties should download the document from our website. Anyone who has difficulty downloading the document should contact Adelard to discuss other options.
  • The manual may be used freely by registered users, both for commercial and non-commercial use.
  • While Adelard believes the content to be accurate, it accepts no responsibility for any consequence of use, either direct or indirect. Use of the manual implies acceptance of this and all other conditions.
  • The content of the manual may not be reproduced in any format (other than for backup purposes) without agreement from Adelard in writing.
  • The document may be used in support of both academic teaching and research, and in both cases some of the above restrictions may be waived.
  • The document is available free of charge in softcopy only, which can be requested after filling out the form below. Hard copy versions are available at a nominal reproduction charge.

Why a Safety Case Manual?

A safety related system must have a safety case; this is explicitly required by licensing regulations in a wide range of industries and equivalent requirements are given in many standards such as IEC 61508. The safety case should:

  • demonstrate an adequate level of safety
  • ensure safety is maintained throughout the lifetime of the system
  • minimise project risk

Despite these requirements, there is little published guidance on developing safety cases.

Adelard has now written a manual describing how to define and develop a safety case. This manual is based on many years of experience of developing safety cases, and on assessing safety cases as Independent Safety Assessors. The technical basis of the manual is the product of CEC and industry sponsored research.

This manual will be useful to: safety case developers both experienced and new; assessors and evaluators of safety related systems; project managers and procurers of safety related systems; designers of safety related systems; and anyone with an interest in the safe operation of a safety related system.

Scope of the Adelard Safety Case Development Manual

ASCAD defines a generic approach which is applicable across a wide range of technologies. The details of the approach are concerned with safety cases for computer based command, control and protection systems. The manual covers constructing a safety case for a new system and retrospective development of a safety case for an existing system. The use of COTS (commercial off-the-shelf software) in a safety related system is also covered.

Safety Case Definition

Adelard defines a safety case as:

A document body of evidence that provides a demonstrable and valid argument that a system is adequately safe for a given application and environment over its lifetime.

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