Question

In the context of ISO 26262, what is the formal definition of &#x27;Single-Point Fault Metric&#x27; (SPFM) required to achieve an ASIL D rating?

Accepted Answer

The Single-Point Fault Metric (SPFM) is a numerical measure used in ISO 26262 to verify that a hardware design can effectively handle hardware failures, specifically those that could lead directly to a hazardous event without any other intervening faults. A single-point fault is a failure in a hardware component that is not covered by a safety mechanism and leads directly to a violation of a safety goal, which is a high-level objective to prevent hazardous behavior by the vehicle. To achieve an ASIL D rating, which is the most stringent automotive safety integrity level representing the highest risk, the SPFM must be greater than or equal to 99%. Think of the SPFM like a safety net percentage: if 100 random parts of your system were to break, the SPFM tells you how many of those failures would be caught or controlled by your safety systems, such as alarms or backup circuits, ensuring the car remains safe even when things go wrong. Mathematically, it is defined as one minus the sum of the failure rates of all single-point faults not detected by safety mechanisms, divided by the sum of all hardware failure rates. By requiring at least 99% coverage, the standard ensures that essentially every potential single-point failure is identified and mitigated to protect the driver and passengers in the highest-risk scenarios.

Home → All Courses → Engineering and Technology Courses → "Electric & Autonomous Vehicles" → Flashcard

In the context of ISO 26262, what is the formal definition of 'Single-Point Fault Metric' (SPFM) required to achieve an ASIL D rating?