Governing Standards
ISO 3691-4:2023
The dominant international standard. Updated from 2020 edition.
- Scope: Driverless industrial trucks and their systems. Covers AGVs, AMRs, and AGCs.
- Size: 82 pages, 6 sections, 5 annexes
- Status: Current edition. U.S. buyers increasingly demand ISO 3691-4 alignment over ANSI B56.5.
- Key requirement areas: Speed control, braking systems, personnel detection, operating zones, safety function performance levels
ANSI/ITSDF B56.5-2024
U.S. national standard. Updated 2024.
- Scope: Driverless automatic guided industrial vehicles and automated functions of manned industrial vehicles
- Covers: Design, operation, maintenance requirements
- Relationship to ISO 3691-4: ISO 3691-4 now dominates for intelligent mobile robots. B56.5 applies to the broader AGVS category. U.S. market is converging toward ISO 3691-4 for stricter provisions.
EN 1525:1997 — European Status (September 2026)
EN 1525:1997 remains the only CEN-published standard for driverless industrial trucks in Europe; no replacement CEN standard had been formally issued as of September 2026. Key context:
- EN 1525 was listed for presumption of conformity under the old Machinery Directive (98/37/EC) only — it was never a harmonised C-type standard under the current Directive (2006/42/EC), meaning there has been no harmonised European standard for new AGV/AMR deployments.
- ISO 3691-4 adoption path at CEN: After ISO 3691-4:2020 was published, CEN experts assessed it as requiring redraft before adoption as prEN ISO 3691-4. That process is ongoing. prEN ISO 3691-4 is in CEN draft status; no adoption date was published as of September 2026.
- ISO/DIS 3691-4 is a further revision of ISO 3691-4:2023 in ISO draft-international-standard stage; expected to supersede the 2023 edition when finalized.
- Practical implication: EU-deployed AGV/AMR projects should reference ISO 3691-4:2023 for technical requirements (it is used as a de facto reference by AHJs and notified bodies) while noting that no harmonised CEN standard currently exists. Do not cite “EN 1525:1997 (current)” in client deliverables — it predates all modern AGV navigation and safety technology.
Key Technical Requirements
Detection Zones (Safety Laser Scanners)
Safety laser scanners create layered detection zones:
| Zone | Trigger | Description |
|---|---|---|
| Warning field | Deceleration | Outer zone; vehicle slows |
| Safety/protective field | Full stop | Inner zone; vehicle stops |
| Monitored area | Combined | Total perimeter of detection |
- Minimum clearance: 0.5m (19.7 inches) between AGV/load and external structures
- Protective fields must adapt to vehicle speed and load condition
- Scanner cost: ~$2,500–$3,500 each (2024 market estimate; pricing varies with detection range and field-set count)
- Field sets per scanner: 4 (standard) to 32+ (advanced models)
- Systems typically use at least 2-3 safety fields simultaneously
Speed Limits by Zone
| Zone Condition | Maximum Speed |
|---|---|
| No laser detection coverage | 0.3 m/s |
| Hazard zone with active scanner | 1.2 m/s |
| Standard operating zone | 2 m/s (typical maximum) |
| Restricted zone (ISO 3691-4 higher-speed exception) | Higher speed allowed with detailed hazard analysis and additional measures |
Emergency Stop Requirements
- E-stop device required on every AGV
- Must be clearly visible, distinguishable, and accessible from any side
- Located within 600mm reach from any side of the vehicle
- Number and position determined by vehicle shape and dimensions
Bumper Requirements
- Mechanical bumpers cover areas not monitored by safety laser scanners
- Contact speed at bumper: maximum 0.3 m/s (18 m/min)
- Must safely stop vehicle within the bumper’s collapsible range
Braking Systems
- Must activate automatically on power supply interruption
- Must stop the truck within the operating range of the personnel detection zone
- Must function under all load conditions and gradients
Safety Function Performance Levels
ISO 3691-4 defines performance levels (PLd or higher) for key safety functions including:
- Personnel detection
- Speed monitoring
- Braking initiation
- Zone transitions
Compliance Responsibility Framework
ISO 3691-4 assigns shared responsibility:
- Manufacturer: Design and build to standard requirements
- Integrator: System design, hazard analysis, site-specific configuration
- Operator: Ongoing safe operation, maintenance, restricted zone access control
Practical Implications for Specifying
- Confirm CE marking (Europe) or UL listing (U.S.) for the vehicle
- Request ISO 3691-4:2023 compliance documentation from vendor
- Site hazard analysis required before installation (integrator responsibility)
- Restricted zone access controls (barriers, light curtains) are site scope, not vehicle scope
- Safety scanner field sets must be configured per final layout - not pre-configurable from catalog
Autonomous Reach-Truck Safety Certification (TWA project spec, 2024)
Source-derived from the Third Wave Automation product safety documentation (v5.0); see third-wave-automation. A worked example of the certification stack for a shared-autonomy autonomous forklift:
- End-product: ANSI/ITSDF B56.5-2019 (driverless/automated industrial vehicles), ISO 3691-4, UL 583 Type E (electrical).
- Functional safety: ISO 13849-1/-2 at Performance Level d, Category 3 (the machinery-directive PL/CAT framework, not an IEC 61508/62061 SIL rating; PL d roughly maps to SIL 2 but is a different regime). No CE mark (US-market: FCC Part 15 Class A, no EU cert).
- Cybersecurity: IEC 62443. Laser (LiDAR): IEC 60825-1. Lighting: OSHA 29 CFR 1910.178(h)(2), >= 2 lumens/sq ft.
- Sensing/stopping: three 3-D LiDARs, 360-degree obstacle detection to ~5 m; braking distance 2.5 m (8 ft) at max velocity (level/dry/clean, 4,000 lb); three wired cab e-stops + deadman + mechanical parking brake.
[!practitioner-note] Documented “cannot detect” limits become the customer’s administrative burden The product explicitly does not track humans/objects under a raised carriage, does not predict an oncoming vehicle’s path (manual operators must yield to the robot), and does not detect another truck’s low forks. The OEM offloads these onto ~18 mandatory customer administrative safety policies. And the multi-layer safety relies on a constant Wi-Fi UDP heartbeat that keeps the truck moving - so Wi-Fi coverage is a safety-critical dependency, not a convenience. When comparing vendors, do not treat “PL d Cat 3” and “SIL 2” as interchangeable.