Scope and Tailoring
The applicability path through ISO 26262: does the standard govern your product, which parts bind your role, and how much of the lifecycle you may tailor away - with the rationale to defend it.
- Chapters
- 14
- Chapters
- Worked product examples
- 7
- Worked product examples
- ISO 26262 parts mapped
- 12
- ISO 26262 parts mapped
- Decision checklist
- 1
- Decision checklist
Quick answers
- What is tailoring in ISO 26262?
- Tailoring is the controlled adaptation of the ISO 26262 safety lifecycle to a specific project: under ISO 26262-2 §6.4.5, planned safety activities may be omitted or performed differently, provided a rationale shows the adaptation is appropriate and sufficient to achieve functional safety. Tailoring is not an exemption - the rationale is itself a work product, recorded in the safety plan and examined during the functional safety assessment. Legitimate drivers include the development context, reuse of proven elements, and the nature of the item; convenience and schedule pressure are not rationales an assessor will accept.
- Does ISO 26262 apply to prototypes and low-volume vehicles?
- The standard targets series-production road vehicles, which gives prototypes and special-purpose vehicles genuine arguments for doing less - but each argument is worth less than teams hope. The course examines three such arguments and their limits: a prototype still creates real risk the moment it drives on public roads among other people, low volume changes exposure but not hazard severity, and special-vehicle carve-outs are narrower than their reputation. What survives is a tailored lifecycle with a written rationale, not a blanket exemption.
Why it pays for itself
Answer applicability once, defensibly
The scope gate plus the neighbours map gives you a written yes-or-no on whether ISO 26262 governs your product, with the border to SOTIF, security, and quality drawn explicitly.
Tailor without an assessor fight
Learn the §6.4.5 permission and its limits: what may be omitted or performed differently, what rationale clears the appropriate-and-sufficient bar, and where the tailoring record must land.
Read only the parts you owe
The twelve-parts map filtered by role tells an OEM system engineer, a supplier software lead, or a hardware developer exactly which clauses bind them - and which are guidance.
What you’ll be able to do
Decide Applicability Defensibly
Run any product through the scope gate and answer whether ISO 26262 governs it, with the reasoning written down.
Navigate the Twelve Parts
Know which parts and clauses are binding for your role and which are guidance, so you read what you owe and skip what you do not.
Classify the Development Context
Distinguish in-context development, SEooC on assumptions of use, and pre-existing elements, and pick the matching lifecycle entry point.
Tailor Within the Rules
Use the §6.4.5 permission correctly: omit or adapt activities with a rationale that is appropriate and sufficient to achieve functional safety.
Handle QM Verdicts Correctly
Treat QM as a managed outcome with coexistence criteria instead of an exemption from the standard.
Write a Rationale That Survives Assessment
Document scope and tailoring decisions in the safety plan so an assessor can follow the argument years later.
Chapter by chapter
- 01
Start Here
Three different questions usually asked as one: does ISO 26262 apply at all, which parts matter to you, and how much of the lifecycle you must actually perform.
- Three questions
- Applicability path
- How to read the standard
- 02
The Scope Gate
Does the standard govern this product at all: series-production road vehicles, safety-related E/E systems, hazards caused by malfunctioning behaviour, and the explicit exclusions and adaptations.
- Series production
- Malfunction focus
- Exclusions
- 03
The Neighbours
What ISO 26262 is deliberately not about and which discipline owns it instead - performance limitations, security, quality - so scope arguments stop at the right border.
- Neighbouring standards
- Ownership map
- Border discipline
- 04
The Item Boundary
The item definition as the decision that quietly sets every other decision: boundary, interfaces, and assumptions that HARA and the whole safety case inherit.
- Item definition
- Boundary choices
- Downstream inheritance
- 05
The Twelve Parts Map
What is in the box: all twelve parts of ISO 26262 mapped, and which bits are actually binding requirements versus guidance you may consult.
- All 12 parts
- Binding vs guidance
- Reading order
- 06
Your Role, Your Parts
The same map filtered down to what you personally owe - which parts and clauses bind an OEM system engineer, a supplier software lead, or a hardware developer.
- Role filter
- What you owe
- Part relevance
- 07
Development Contexts
In context, out of context, or something that already exists: SEooC development on assumptions of intended use, and the Clause 15 and 16 interfaces for out-of-scope and external systems.
- SEooC
- Assumptions of use
- Clauses 15-16
- 08
Tailoring: Rules and Limits
The §6.4.5 permission to omit or perform activities differently, the rationale bar of appropriate and sufficient to achieve functional safety, and where tailoring stops.
- §6.4.5 permission
- Rationale bar
- Hard limits
- 09
QM, ASIL and the Grey Zone
QM is not an ASIL and not an exemption: what a QM verdict actually requires, coexistence criteria, and how sub-elements inherit ASIL without them.
- QM is not exemption
- Coexistence criteria
- ASIL inheritance
- 10
Tailoring for Change and Reuse
Almost nothing is a clean sheet and the standard knows it: impact analysis for modifications, carryover of proven elements, and tailoring a lifecycle around the delta.
- Impact analysis
- Carryover
- Delta-driven lifecycle
- 11
Prototypes, Low Volume and Special Vehicles
Three arguments for doing less and what each one is actually worth - including why a prototype driving on public roads changes the calculation.
- Prototype caveat
- Low volume
- Special vehicles
- 12
Worked Examples
Eleven chapters of theory applied to seven real products, from a body control module to a cloud-connected feature, each run through the whole applicability machine.
- Seven products
- Full applicability runs
- Common pattern
- 13
Documenting the Rationale
Where the decisions land and who reads them: the safety plan, the tailoring record per 6.4.5 to 6.4.13, and writing rationales for the assessor rather than the drawer.
- Safety plan
- Tailoring record
- Assessor audience
- 14
Pitfalls and the Decision Checklist
Everything above turned into something you can use on Monday: the recurring scope and tailoring mistakes plus a decision checklist for your own product.
- Common pitfalls
- Monday checklist
- Decision flow
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Expert plan pricingSeven Products Through the Whole Machine
Chapter 12 applies the full applicability path - scope gate, item boundary, context, tailoring, rationale - to seven real product types, then draws out what they all have in common.
- A body control module - in-context development with freedom-from-interference questions
- A radar sensor - a perception component at the SOTIF border
- An electric parking brake actuator - actuator safety with a clear item boundary
- A software library - pre-existing software heading for qualification
- An SoC or an IP block - SEooC development on assumptions of use
- A test bench or a flashing tool - tool confidence instead of item scope
- A cloud-connected feature - deciding where the vehicle item ends
Unlock in course
Who this guide is for
- Engineers facing ISO 26262 for the first time on a concrete product
- Safety managers writing the safety plan and its tailoring rationale
- Startups and prototype teams deciding how much lifecycle they owe
- Suppliers developing SEooC elements on assumptions of use
Frequently Asked Questions
Common questions about Scope and Tailoring
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Where this topic leads next.
- FoundationsDevelopment Interface AgreementLearn how to define clear safety responsibilities and evidence exchange between OEM and supplier per ISO 26262-8. Covers DIA content structure, RASIC matrix, lifecycle from initiation to production, and assessment coordination.
- FoundationsISO 26262 vs Other Safety StandardsLearn how ISO 26262 compares with IEC 61508, DO-178C, EN50128, ISO 13849, and SOTIF across key dimensions. Covers risk classification differences, lifecycle approaches, V&V strategies, and multi-standard compliance.
- Concept phaseItem Definition & Concept-Phase InitiationGet the first ISO 26262-3 step right: define the item boundary, interfaces, operating modes, and assumptions of use that HARA, safety goals, and the whole safety case inherit from the concept phase.