Frequently asked questions

Here you will find answers to some of the most common questions we get asked about MISRA and MISRA activities.

MISRA publications

How do the MISRA Safety Analysis Guidelines relate to ISO 26262?

ISO 26262 Road Vehicles - Functional safety is intended as an automotive interpretation of IEC 61508. As both MISRA SA and ISO 26262 are based on IEC 61508, there is a general agreement in their respective approaches. However, MISRA SA does not cover all the stages of the safety lifecycle, but rather provides a framework that can be used to introduce functional safety management, supported by an appropriate process. Within this framework, the requirements of either IEC 61508 or ISO 26262 can be met.

While ISO 26262 gives specific requirements, these are often presented without explanation or justification. MISRA SA explains and justifies specific processes and activities. For example, ISO 26262 Part 3 Clause 5 "Item Definition" contains 3 requirements expressed in 224 words. The equivalent MISRA SA activity "Model the system and environment" covers some 10 pages. Similarly ISO 26262 Part 3 clauses 7.4.1–7.4.4, which cover hazard identification, contain 9 requirements expressed in 412 words. The MISRA SA activity "Identify hazards" covers 7 pages.

Will the 1994 MISRA Guidelines be updated?

MISRA has started work on a version 2 but there are potential changes to international standards, including ISO 26262 "Road vehicles - Functional safety", and Edition 2 of IEC 61508 both of which released public drafts in 2009. We therefore plan to review the structure and content of a revised "Development Guidelines" once ISO 26262 and IEC 61508 edition 2 have been published. In the meantime MISRA SA gives some specific guidance on safety management that can be used to establish processes meeting the requirements of these standards. See also the questions relating specifically to IEC 61508 and ISO 26262.

Does MISRA offer training on the use of its documents?

Not at the present time, although some of the member companies may do.

Can I still get the 1994 MISRA Guidelines?

You can purchase a PDF version from the webstore. Alternatively ISO supply it as ISO/TR 15497.

How do the MISRA Guidelines relate to IEC 61508?

IEC 61508 Functional safety of electrical/electronic/programmable electronic safety-related systems is a generic standard. At the time of writing Development Guidelines for Vehicle Based Software IEC 61508 had not been published, although the authors did consider earlier drafts of the standard. Many of the principles of the standard are embodied in the Guidelines with an automotive focus where appropriate. The MISRA Safety Analysis guidelines provide a "mapping" between the IEC 61508 safety lifecycle and automotive product lifecycles.

Aren't the 1994 MISRA Guidelines a bit out of date?

Development Guidelines for Vehicle Based Software was published in November 1994 with an anticipated 10-year lifespan (10 years order of magnitude, not precisely 10 years).

What publications are there? What's the difference?

There are ten principal MISRA publications:

  • Development Guidelines for Vehicle Based Software - also known as "The MISRA Guidelines" - (published November 1994)
  • Guidelines for the Use of the C Language in Vehicle Based Software - also known as "MISRA C" - (published April 1998)
  • MISRA C:2004 - Guidelines for the use of the C language in critical systems (published October 2004)
  • Software Readiness for Production (MISRA SRfP) (published March 2006)
  • Guidelines for safety analysis of vehicle based programmable systems (MISRA SA) (published November 2007)
  • Modelling style guidelines for the application of TargetLink in the context of automatic code generation (MISRA AC TL) (published November 2007)
  • Guidelines for the application of MISRA-C:2004 in the context of automatic code generation (MISRA AC AGC) (published November 2007)
  • MISRA C++:2008 - Guidelines for the use of the C++ language in critical systems (published June 2008)
  • Generic modelling design and style guidelines (MISRA AC GMG) (published May 2009)
  • Modelling design and style guidelines for the application of Simulink and Stateflow (MISRA AC SLSF) (published May 2009)

There are also supporting reports for the MISRA Guidelines, a Technical Corrigendum and Exemplar Suite for MISRA-C:2004 and an introduction to the autocode guidelines (MISRA AC INT).

The MISRA Guidelines describe the approach to developing the embedded software in a safety-related automotive system. MISRA C was produced to meet a specific technical requirement of the MISRA Guidelines, namely the use of a restricted subset of a standardized structured programming language. The MISRA AC family of documents apply a similar approach to the graphical programming languagues and toolchains used in model-based development. MISRA SA extends the MISRA Guidelines, particularly in giving extended detailed advice on the sections on Integrity and Safety Analysis, as well as presenting additional advice on other parts of safety management and the safety lifecycle.