Mobile Robot Safety Standards: Understanding ISO 3691-4 and ANSI/RIA R15.08 Implementation

Mobile robots are transforming logistics and manufacturing, but their proximity to human workers introduces new safety challenges. Traditional methods like fencing off machines don't work when AGVs and IMRs need to move through shared, dynamic spaces.

Enter ISO 3691-4 and ANSI/RIA R15.08—two complementary safety standards that provide a robust framework for enabling safe, intelligent mobile robot deployment. As of 2025, ISO 10218 explicitly defers to ISO 3691-4 for mobility behaviors in mobile manipulators, underscoring its relevance.

1. A Shifting Landscape in Safety Standards

While CE marking in Europe leans on ISO/IEC/EN standards, ANSI/RIA standards guide North American compliance. Increasingly, U.S. buyers are demanding ISO 3691-4 alignment due to its stricter provisions—especially for “gray area” robots like autonomous forklifts.

Standards like ANSI/ITSDF B56.5 once applied to AGVs, but ISO 3691-4 now dominates for intelligent mobile robots (IMRs).

2. Evolution from EN 1525 to ISO 3691-4

Where EN 1525 was a guideline, ISO 3691-4 is a full safety architecture. Key components include:

Primary Safety Control (PLd)

• Requires PLd-rated systems (ISO 13849) for functions like personnel detection
• Necessitates redundant controllers, fault detection, and independent monitoring

Zone Management

Three zones with specific safety provisions:

• Operating Zone: Full detection and restart protocols
• Restricted Zone: Speed-limited operation and warnings
• Confined Zone: Physical barriers and interlocks

Vendors like 3Laws Robotics support mathematical zone mapping for dynamic reconfiguration.

3. ANSI/RIA R15.08: Complementary Framework for IMRs

R15.08 goes beyond 3691-4 by addressing IMR-specific use cases through three parts:

R15.08-1: Base Robot Requirements

• Hazard identification and risk reduction
• Emergency stop protocols
• Safety-rated monitored stop functions
• System architecture and stability monitoring

R15.08-2: System Integration

• Deployment design, traffic management, and facility safety system coordination
• Multi-robot coordination strategies

R15.08-3: Application-Specific Requirements

• Special applications, environmental considerations, and safeguarding strategies

4. Risk Assessment in R15.08-1

The standard emphasizes a comprehensive approach to hazard analysis:

Key Considerations

• Intentional Interactions: Teaching, loading, tool change
• Unintentional Interactions: Pedestrian safety, path conflicts
• Environmental Hazards: Floor grates, tight corners
• Failure Modes: Loss of localization, control system faults
• Foreseeable Misuse: Unauthorized software changes, operator errors

Risk Reduction Process

1. Elimination by Design
2. Substitution and Engineering Controls
3. Protective Devices
4. Administrative Controls
5. Validation and Continuous Improvement

📌 Saphira AI can assist with hazard identification and suggesting mitigation measures tailored to your design.

5. Severity Classification in R15.08

R15.08 introduces a four-tier severity system:

• S1: Minor injuries
• S2: Reversible injuries
• S3: Permanent injury
• S4: Fatal/life-threatening

This nuanced framework enables more granular risk modeling than the simpler S1/S2 tiers in ISO 13849-1.

6. Fleet-Level Safety Assessment

Additional IMR fleet safety concerns include:

• Coordinated E-stop response
• Traffic orchestration across robots
• Compatibility with fleet management software

📎 See Chris Soranno’s SICK presentation for detailed fleet safety guidelines in R15.08-2.

7. Harmonization Between Standards

ISO 3691-4 and R15.08 work together seamlessly:

Safety Functions

• Shared emphasis on personnel detection and emergency stops
• R15.08 expands on ISO’s baseline with additional interpretive flexibility

Risk Assessment

• R15.08 uses advanced severity + exposure + avoidance scoring
• ISO maintains foundational simplicity with consistent evaluation processes

System Integration

• Compatible architecture and validation strategies
• Harmonized safety documentation

Operations

• Unified treatment of modes, maintenance, and emergency response

8. Practical Implementation

Combined Approach:

• ISO 3691-4 = foundational safety layer
• R15.08 = robot-specific implementation and deployment guidance

This combo yields a scalable, certifiable framework for IMR safety at both the system and fleet level.

9. The Path Forward

These standards don’t just ensure safety—they enable innovation.

By aligning with ISO 3691-4 and R15.08:

• You reduce liability
• Accelerate deployment
• Enable true human-robot collaboration

🌟 The convergence of global standards is paving the way for smart, responsive, and safe industrial automation.

---

Ready to Streamline Your Compliance?

Need help performing HARA, generating Safety Requirements Specs, and building a complete Compliance Case for certification? 🛠️ Saphira AI can coordinate your entire ISO 3691-4 and R15.08 workflow—from risk assessment to final report generation.

📩 Contact us at contact@saphira.ai to get started!