What is the difference between functional safety and Sotif?

In the field of automotive development, two crucial concepts that manufacturers and engineers should be familiar with are functional safety (FuSa) and Safety of the Intended Functionality (SOTIF). While both strive to ensure the safety of vehicles and their occupants, they address different aspects of vehicle safety. In this article, we will explore the differences between functional safety and SOTIF.

Functional Safety (FuSa)

Functional safety, also known as FuSa, focuses on designing and implementing systems that prevent or mitigate hazards resulting from malfunctions or failures in safety-related functions. The goal of functional safety is to ensure that these safety functions operate correctly, even in the presence of faults or errors.

FuSa primarily aims to reduce the risk of hazardous events caused by hardware failures, software errors, or human mistakes. This involves the use of safety principles, safety goals, risk assessment methods, and implementing safety measures throughout the entire product lifecycle.

Safety of the Intended Functionality (SOTIF)

While functional safety concentrates on potential hazards due to system malfunctions, Safety of the Intended Functionality (SOTIF) addresses hazardous situations arising from the limitations of the system's intended functionality and design.

SOTIF takes into account scenarios where the system operates as intended but may encounter uncertain conditions or mismatches with the surrounding environment. These situations can result in unsafe outcomes, even though no obvious failures or malfunctions have occurred.

To achieve SOTIF, engineers must consider environmental factors, external influences, and potential human-machine interactions. It requires extensive analysis of possible edge cases, such as complex traffic situations, unexpected road conditions, or sensor limitations.

Differences and Complementarity

While functional safety and SOTIF address different aspects of vehicle safety, they are complementary to each other. FuSa aims to ensure that the system performs its intended safety functions even in the presence of faults, errors, or failures. On the other hand, SOTIF focuses on scenarios where the system may not encounter any faults, but still presents potential safety risks due to ambiguous or uncertain situations.

In practice, achieving optimal safety requires considering both functional safety and SOTIF. Manufacturers must implement robust functional safety measures to detect and mitigate potential failures, while also accounting for possible hazards related to system limitations and environmental influences.

By integrating both approaches, automakers can enhance the overall safety of vehicles, providing better protection to occupants and improving the reliability of advanced driver-assistance systems (ADAS) and autonomous driving technologies.

In conclusion, functional safety and SOTIF are critical components of automotive safety. While functional safety emphasizes mitigating hazards caused by system failures, SOTIF focuses on the system's limitations and the potential risks they might introduce. Achieving comprehensive vehicle safety requires an integration of both approaches to minimize accidents and maintain passenger well-being.