Implement safety-critical isolation using safety island architecture

How safety islands support functional safety

In automotive systems, a non-safety ECU (Electronic Control Unit) typically runs non-critical tasks such as infotainment or navigation. A safety island, by contrast, is dedicated to executing safety-critical control logic (for example, braking and steering) with strong isolation, redundancy, and determinism.

The table below compares the characteristics of an ECU and a safety island in terms of their role in supporting functional safety.

This comparison shows why safety-critical software depends on dedicated hardware domains to meet functional safety goals.

If the main processor fails or becomes inoperable, a safety island can take over critical safety functions such as deceleration, stopping, and fault handling to prevent catastrophic system failures.

Key capabilities of a safety island

• System health monitoring continuously monitors the operational status of the main processor (for example, the ADAS control unit) and detects potential errors or anomalies
• Fault detection and isolation independently detects failures and initiates emergency handling for overheating, execution faults, or unresponsiveness
• Essential safety functions continue to operate, even if the main system crashes. A safety island can execute fallback operations, such as:
  • Autonomous Vehicles → safe stopping (fail-safe mode)
  • Industrial Equipment → emergency power cutoff or speed reduction

Why a safety island matters for functional safety

A safety island provides a dedicated environment for executing critical safety functions. Its key characteristics include:

• Acting as an independent redundant safety layer

  • Operates safety logic independently of the main processor

• Supporting the ASIL-D safety level

  • Enables the system to meet the highest ISO 26262 requirements for critical operations

• Providing independent fault detection and recovery mechanisms:

  • Fail-safe: activating a minimal-risk mode, such as limiting vehicle speed or switching to manual control
  • Fail-operational: allowing high-integrity systems, such as those in aerospace or autonomous driving, to continue functioning under fault conditions

Safety islands play a key role in enabling ISO 26262 compliance by isolating safety-critical logic from general-purpose processing. They’re a proven solution for improving system determinism, fault tolerance, and fallback behavior.