ISO 19725:2026

Overview

ISO 19725:2026 - Road vehicles - Steer-by-wire systems - System safety guidelines provides essential safety requirements for the implementation of steer-by-wire (SbW) systems in passenger cars and light commercial vehicles intended for series production. This international standard, developed by ISO, sets out a framework to help vehicle manufacturers and system suppliers manage the unique safety challenges associated with SbW technology. While it outlines necessary, but not sufficient, requirements, ISO 19725:2026 is designed to complement - not replace - the ISO 26262 series of functional safety standards. The document addresses manual driving modes where the driver retains physical control via the steering wheel and does not cover automated lateral vehicle control or hands-free misuse.

Key Topics

• System Boundaries and Definitions

  • Establishes clear boundaries for SbW systems, focusing on road wheel actuators (RWA), hand wheel actuators (HWA), and driver input via a steering wheel.
  • Provides terminology and concepts for consistent application across manufacturers.

• Safety Goals

  • Defines critical safety objectives for SbW systems:
    • Preventing self-steering while driving
    • Maintaining steerability at all times
    • Ensuring continuous feedback torque to the driver
    • Avoiding unintentional blocking of the steering wheel
    • Preventing loss of synchronization between driver input and actuator response

• Controllability and Fault Management

  • Outlines requirements for driver controllability following the first detected fault, including system responses and fault-tolerant operation.
  • Introduces degradation concepts and transitions to manage system performance and safety after faults occur.

• System Availability

  • Specifies minimum performance and availability criteria, including the use of redundancies and mechanisms to maintain safety in case of electrical or mechanical failures.

• Testing and Assessment

  • Describes procedures for assessing vehicle controllability and lateral performance through defined maneuvers and test sequences, especially under degraded or faulted conditions.

Applications

ISO 19725:2026 is invaluable for the design, validation, and safety assurance of steer-by-wire systems in modern vehicles. Its practical applications include:

• Vehicle Design and Engineering: Provides guidelines for integrating SbW systems while ensuring maintainable safety across all operational modes.
• System Supplier Development: Helps component suppliers to align their products with international safety expectations and OEM requirements.
• Product Verification and Testing: Supports OEMs and testing organizations in validating the controllability, feedback, and reliability of SbW-equipped vehicles.
• Regulatory Compliance: Assists manufacturers in demonstrating due diligence regarding system safety, especially in alignment with ISO 26262 functional safety processes.
• Risk Assessment: Encourages comprehensive hazard analysis and risk assessment for all SbW failure modes, including electrical and mechanical faults.

Related Standards

To ensure complete coverage of functional safety for road vehicles, ISO 19725:2026 should be used in conjunction with other core automotive standards, including:

• ISO 26262 series: Road vehicles - Functional safety (essential for full safety lifecycle management)
• ISO 15037-1: Road vehicles - Vehicle dynamics test methods - Part 1: General conditions for passenger cars
• UN Regulation No. 79: Provisions concerning steering equipment

By following ISO 19725:2026 along with these related standards, manufacturers and suppliers can achieve robust, internationally recognized safety levels for steer-by-wire systems, supporting market trust and regulatory approval for next-generation vehicle steering technologies.