ISO 26262 – automotive functional safety

Modern vehicles are packed with electronics—from engine control systems and driver-assistance functions to sensors and actuators. Ensuring their reliable operation is critical to safety. The ISO 26262:2018 Road Vehicles – Functional Safety standard is an international benchmark that defines functional safety requirements for electrical and electronic (E/E) systems in road vehicles. It is an automotive-specific adaptation of the general standard IEC 61508 (which addresses functional safety across all industries), tailored specifically to the realities of automotive engineering. The aim of ISO 26262 is to prevent unacceptable risk arising from faulty operation of electronic systems—by defining risk assessment processes and implementing safety measures that reduce risk to an acceptable level. In other words, the standard addresses potential hazards caused by electronic failures in vehicles and explains how to mitigate them.

ISO 26262 was first published in 2011, initially limited in scope to passenger cars with a mass up to 3.5 tonnes. The second edition from 2018 introduced major extensions—covering all road vehicles (trucks, buses, motorcycles, etc., excluding mopeds) and adding new sections addressing, among other things, semiconductor components. As a result, the standard reflects the growing complexity and diversity of electronic systems in modern automotive applications, taking their specific challenges into account.

IEC 61508 as the foundation: It is worth emphasizing that ISO 26262 is derived directly from its parent standard IEC 61508, but has been tightly aligned with the needs of the automotive industry. This means the approach to risk assessment, hazard classification, and the selection of safety measures is tailored to typical vehicle operating conditions. The standard defines, among other things, a dedicated automotive safety lifecycle and introduces domain-specific concepts such as the Automotive Safety Integrity Level described below.

ISO 26262 structures the entire functional safety assurance process into a product lifecycle—from concept through design, integration, and testing, all the way to production, operation, and decommissioning. The standard indicates what activities should be carried out at each of these stages to identify potential hazards and minimize the risk of failures that could create dangerous situations.

ASIL levels – risk classification in ISO 26262

One of the core concepts in ISO 26262 is ASIL (Automotive Safety Integrity Level), i.e., the level of functional safety integrity in automotive applications. ASIL is a scale used to assess the risk associated with a potential failure of a given system—it determines how stringent the safety measures must be to reduce risk to an acceptable level. The standard defines four ASIL levels: A, B, C, D (from lowest to highest) and the QM (Quality Management) category, which indicates that no safety requirements beyond standard quality processes apply.

Determining the ASIL level: The ASIL level is established during hazard analysis and risk assessment (Hazard Analysis and Risk Assessment, HARA). For each potential hazard, three key factors are considered: Severity—the seriousness of potential consequences (e.g., injuries), Exposure—how often situations conducive to the failure occur, and Controllability—the driver’s ability to manage the situation. The combination of these factors translates into a risk classification. Levels from ASIL A to ASIL D reflect the maximum severity of failure consequences, the likelihood of injury, and the chance of controlling the event. Based on these parameters, the appropriate safety integrity level is assigned for a given hazard—or QM if the risk is low enough that normal design practices are sufficient.

The role of ASIL in risk assessment: Selecting the correct ASIL level is critical because it determines how rigorous the system development process must be. The higher the ASIL, the more stringent the requirements the design has to meet—both in terms of the hardware/software architecture and the processes for development, testing, and validation. The standard clearly requires that higher ASIL levels be supported by more detailed documentation, stricter design rules, more thorough safety analyses, and independent reviews of the work results. In practice, a high ASIL often drives the inclusion of redundancy and diagnostic mechanisms in the design so that a single fault does not lead to the loss of a safety function. For illustration: life-critical systems such as airbags, the ABS system, or electric power steering are typically classified as ASIL D, because their failure poses a serious risk to passengers. Less critical functions, such as rear position lights, may be assigned ASIL A or even treated as QM, because a potential fault does not create significant risk. This approach makes it possible to focus the greatest engineering effort where it is most needed—on systems that directly affect people’s safety.

Structure of ISO 26262:2018 – Parts 1–10

ISO 26262 (2018 edition) is divided into a series of parts, each focusing on a different aspect of the safety lifecycle. The core of the standard consists of nine normative parts (1–9) plus an additional guidance part (Part 10). The second edition also introduced Parts 11 and 12 covering specific topics (semiconductors and motorcycles, respectively); however, the discussion below focuses on the foundational Parts 1–10, which have universal applicability. The table below presents the individual parts of ISO 26262:2018 along with their titles and subject scope:

(Note: The 2018 edition also added Part 11 – Guidelines on semiconductors and Part 12 – Adaptation of ISO 26262 for motorcycles. Both are supplementary informative documents that extend the scope of the standard to cover these areas.)

As you can see, the structure of ISO 26262:2018 mirrors the individual stages and aspects of the safe-system design process. Parts 3–7 guide engineers through successive phases—from defining the concept and safety requirements, through system design and implementation at the hardware and software levels, all the way to production and product operation. Part 2 ensures that this entire process is carried out under appropriate safety management at both the company and project levels. Part 8, in turn, provides organizational and technical measures (such as configuration management or tool qualification) that support the implementation of safety requirements at every step. Part 9 provides analysis methodologies, ensuring that at no stage do we overlook factors affecting risk (ASIL) and that we identify potential common-cause or latent failures. Taken together, all these elements form a comprehensive functional safety assurance system.

ISO 26262:2018 structures the entire functional safety lifecycle in automotive—from the concept phase, through detailed design and verification, to series production, maintenance, and product decommissioning. As a result, it provides a coherent framework for manufacturers and suppliers: starting with risk analysis and the definition of safety requirements, through implementing those requirements in the designed systems and software, and ending with final testing and in-field product monitoring. Applying this standard ensures that no safety aspect is overlooked—from the highest level of project management down to the smallest technical detail. The result is vehicles equipped with advanced systems that still meet stringent safety criteria, minimizing risk to users.

We understand what ISO 26262-compliant design looks like—from risk analysis through final testing. With our knowledge and experience, we help implement the standard’s requirements at every stage of the project, so functional safety is not an add-on, but an integral feature of your product.