ISO 21448 (SOTIF) Article 3 — SOTIF Principle 4 Scenario Area categories and Sense-Plan-Act Model(2/2).

4 SCENARIO AREAS CATEGORIES

The Scenarios Which are part of relevant use case are classified into four areas

• Area 1 = Known and Not hazardous.
• Area 2 = Known and Hazardous.
• Area 3 = Unknown and Hazardous.
• Area 4 = unknown and Not Hazardous.

Few examples of unknown areas are given below

• Potential triggering conditions are identified but behaviour of the system is unknown.
• Black Swan event (rare and unpredictable event that has a huge impact).

Area 1 (Known and Not Hazardous)

• System behaves safely No action required.

Area 2 Known and Hazardous

• Unsafe system behavior, which is known and requires design improvements and user warnings.

Area 3 Unknown and Hazardous

• Unsafe System behavior and Scenario is unknown, lot of validation and exploration is required.

Area 4 Unknown and hazardous

• System behaves safely, Through testing move this scenario to Area 1.

Goal of SOTIF Activities is

• Perform the risk acceptance evaluation in area 2 based on analysis of intended functionality and convert area 2 to area 1 by fixing the issue.
• Reduce the probability of the unknown scenarios causing the potential hazardous behavior in area 3, to acceptable criterion through adequate verification and validation strategy.

Sense Plan Act Model

Possible Hazardous behavior are closely related to the ability of the system to create sufficiently accurate Environmental Model (Sense), make right decisions (Plan) and Execute control Actions (Act).

Sense:

Perception, the system perceives the environment using Sensors.

Examples:

• Radar detects distance to other vehicles.
• Camera sees traffic signs or pedestrians.
• Lidar creates a 3D map of surroundings.

Plan:

The system process the Sensor data to derive the control Actions.

Examples:

• Decides to brake because an object is in the path.
• Chooses to slow down for merging traffic.
• Plans lane change based on GPS and map data.

Act:

Execute the control Action.

Examples:

• Sends brake command to reduce speed.
• Turns steering wheel slightly for lane centering.
• Activates warning sound for the driver.

Based on Sense Plan Act model, Suitable and capable system architecture to ensure SOTIF can be Selected, So that overall capability and corresponding activities can takes place both at early stages and throughout whole functional development Lifecyle.