The short answer
ISO 3691-4 is the international safety standard for driverless industrial trucks and their systems: automated guided vehicles (AGVs), load-carrying autonomous mobile robots (AMRs), tunnel tuggers and similar machines that move goods without a driver. Its full title is Industrial trucks — Safety requirements and verification — Part 4: Driverless industrial trucks and their systems. It sets the safety requirements a truck and its control system must meet, and how each requirement is verified, across the truck's life. The first edition was published in 2020 and the second, current edition in June 2023. In the European Union its EN ISO version is harmonised under the Machinery Directive, which makes it the reference most AGV and AMR makers design to worldwide.
At a glance
| Item | ISO 3691-4 |
|---|---|
| Full title | Industrial trucks — Safety requirements and verification — Part 4: Driverless industrial trucks and their systems |
| Published by | ISO technical committee ISO/TC 110/SC 2 (safety of powered industrial trucks) |
| Current edition | Second edition, June 2023 (first edition 2020). A revision, ISO/DIS 3691-4, is under development and will replace it; its draft vote closed in September 2026 |
| Covers | Driverless industrial trucks and their control systems, including AGVs, AMRs and tunnel tuggers; trucks with manual or maintenance modes and trucks that carry riders |
| Does not cover | Trucks guided only by mechanical means, remotely controlled trucks, public zones and public roads, explosive atmospheres, and several other cases listed in the scope |
| Legal status | Voluntary; in the EU, EN ISO 3691-4 gives a presumption of conformity with the Machinery Directive 2006/42/EC |
| Related standards | ISO 13849-1 (safety-related control systems), ISO 13482 (personal care robots), ANSI/A3 R15.08 and ANSI/ITSDF B56.5 (North America) |
What the standard covers
The 2023 scope applies to driverless industrial trucks, which it describes as including automated guided vehicles, autonomous mobile robots and tunnel tuggers. It also covers trucks that have an automatic mode started by an operator, trucks that carry riders, trucks with an additional manual mode and trucks with a maintenance mode. It deals with the significant hazards across the truck's life, listed in an annex, and with the truck's system: the control and fleet software that tells it where to go and the site it works in.
The scope is just as clear about what is left out. It does not apply to trucks guided solely by mechanical means, such as rails, or to remotely controlled trucks, which are not driverless. It excludes operation in public zones, where it refers to ISO 13482, and on public roads; explosive atmospheres, nuclear and military use; carrying people other than intended riders; handling dangerous loads such as molten metal; and rider positions more than 1,200 mm above the floor. Noise, vibration and radiation hazards are also outside it.
Safety is shared between maker and site
A theme running through ISO 3691-4 is that a driverless truck is only as safe as the place it runs in. The manufacturer designs the truck and its safety functions and verifies them. The operating zone, the routes, load stations, markings and who is allowed where, is prepared by the user or integrator, and an annex of the standard sets out how to prepare it so that the hazards are removed or controlled. In practice that means a site risk assessment, agreed zones and documented procedures before the trucks go live, and re-checks whenever routes, loads or software change.
Operating zones
The standard asks the site to divide the operating area into zones according to who may be there and what protective measures apply:
- Operating zones shared with people rely on the truck's own personnel detection: it must sense a person in its path and stop before contact.
- Restricted zones are areas, such as some load-transfer stations, that only trained and authorised staff may enter, under conditions set by the risk assessment.
- Confined zones are areas where people are kept out, for example by fencing, so that some of the truck's protective functions can be reduced while it works there.
Zones are marked on the floor and in the documentation, and the truck's behaviour, such as speed and which detection fields are active, changes with the zone it is in.
Personnel detection and test pieces
Where people can be in the truck's path, the truck needs a personnel detection system, usually safety-rated laser scanners, plus bumpers on some designs. Detection is verified with two standard test pieces:
| Test piece | Size | Represents |
|---|---|---|
| Vertical cylinder | 200 mm diameter, 600 mm high | The legs of a standing person |
| Horizontal cylinder | 70 mm diameter, 400 mm long, lying on the floor | A person lying down |
The truck must detect each test piece in its path and stop before touching it, at every speed and load it is allowed to run at. Protective fields therefore grow with speed: a heavier, faster truck needs a longer field because it needs more distance to stop. Where detection has to be muted or reduced, for example when docking at a station, the truck must slow right down; 0.3 m/s is the limit commonly quoted from the standard for that case.
Safety functions and performance levels
Each safety function, such as personnel detection, speed limiting, braking, steering limits, emergency stop and load handling, is implemented in a safety-related control system designed to ISO 13849-1. The standard assigns a required performance level to each function, many of them PL d. It also covers stability, braking performance, warning devices such as lights and sounds that tell people a truck is moving or about to move, battery charging, and modes such as manual and maintenance.
Verification: proving it works
The "verification" in the title means every requirement must be checked by test, measurement or inspection, and the methods are set out in the standard. In practice that covers brake tests, personnel detection tests with the test pieces, checks of protective field sets against the speed and load at each point on the route, and inspection of warning devices and emergency stops. The truck's information for use must tell the site what it has to do: how to prepare zones, which checks to run before each shift and how often to repeat tests. Changes to routes, field sets, software or loads are a reason to verify again.
ISO 3691-4 and other standards
| Standard | What it covers | Who it is for |
|---|---|---|
| ISO 3691-4 | Safety requirements and verification for driverless industrial trucks and their systems | Manufacturers, with duties for the site preparing the operating zone |
| ANSI/A3 R15.08-1 | US safety requirements for industrial mobile robots, published 2020 | Manufacturers |
| ANSI/A3 R15.08-2 | Integrating IMRs into systems and applications, including interaction with workstations and chargers, published 2023 | System integrators; a Part 3 for users is planned |
| ANSI/ITSDF B56.5 | US safety standard for driverless, automatic guided industrial vehicles and automated functions of manned trucks | Manufacturers and users in North America |
| ISO 13482 | Safety of personal care robots, including mobile servant robots | Robots in public and personal settings, outside ISO 3691-4 |
None of these is a communication standard. Interfaces such as VDA 5050, Open-RMF and the MassRobotics interoperability standard say how robots and fleet systems exchange orders and status; they leave safety to each vehicle and to standards such as ISO 3691-4.
What to ask a supplier
- Which standard and edition? Ask whether the truck is designed and verified to ISO 3691-4:2023 or the 2020 edition, and for the declaration or test report that says so.
- Which zones does it assume? Ask which zone types the risk assessment expects at your site and what the truck's speed and detection settings are in each.
- Field sets and stopping distances. Ask for the protective field sizes at each speed and load, and how they were verified.
- Site checks. Ask which checks the information for use requires before each shift and at intervals, and who does them after handover.
- Public areas. If robots will work where the public can walk, as in malls, hotels or hospitals, ask which standard the maker applies, since ISO 3691-4 does not cover public zones.
- UAE approvals. Safety standards are separate from import and radio approvals. See robot import approvals in the UAE.
Where HORMĒ fits
HORMĒ is a Behavioral Intelligence platform for autonomous machines, based in Dubai, United Arab Emirates. Its behavior layer sits above the vendors' own systems and connects machines through VDA 5050, Open-RMF, ROS 2 or a connector written against the manufacturer's own interface, so machines from different vendors run as one fleet under one site model and one set of rules. It does not replace a truck's safety-rated functions, which stay in the vehicle and are verified by its maker under standards such as ISO 3691-4. See what Behavioral Intelligence is, robot fleet management, pricing, and the machines this most often applies to: warehouse robots and autonomous forklifts.
Frequently asked questions
What is ISO 3691-4?
ISO 3691-4 is the international safety standard for driverless industrial trucks and their systems, such as automated guided vehicles (AGVs), autonomous mobile robots (AMRs) that carry loads, and tunnel tuggers. It sets safety requirements and the means of verifying them. The first edition was published in 2020 and the current second edition in June 2023.
Does ISO 3691-4 apply to autonomous mobile robots?
Yes. The 2023 edition names autonomous mobile robots alongside automated guided vehicles and tunnel tuggers as examples of driverless industrial trucks in its scope. It does not cover trucks guided only by mechanical means, remotely controlled trucks, or trucks working in public zones or on public roads.
Is ISO 3691-4 mandatory?
ISO standards are voluntary. In the European Union, the EN ISO 3691-4 version is harmonised under the Machinery Directive 2006/42/EC, so a truck designed to it is presumed to meet the matching essential requirements of the law. From 20 January 2027 the EU Machinery Regulation (EU) 2023/1230 replaces the directive. Other countries and individual buyers may reference it in contracts or local rules.
What test pieces does ISO 3691-4 use for personnel detection?
Personnel detection is verified with two test pieces: a vertical cylinder 200 mm in diameter and 600 mm high, representing a person's legs, and a horizontal cylinder 70 mm in diameter and 400 mm long lying on the floor, representing a person lying down. The truck must stop before it touches either one.
What is the difference between ISO 3691-4 and ANSI/A3 R15.08?
ISO 3691-4 is the international standard for driverless industrial trucks. ANSI/A3 R15.08 is a US standard for industrial mobile robots: Part 1 (2020) sets requirements for manufacturers and Part 2 (2023) for system integrators, with a Part 3 for users planned. In North America, ANSI/ITSDF B56.5 also covers driverless and automated guided industrial vehicles.
Does ISO 3691-4 cover delivery robots in malls and hotels?
No. ISO 3691-4 excludes trucks operating in public zones and points to ISO 13482, the safety standard for personal care robots, for those settings. Robots in hotels, malls and hospitals open to the public are usually assessed against other standards, depending on the robot and the site.
This page explains the standard in general terms and is not a substitute for the standard itself or for a site risk assessment. Check the current documents before relying on any detail. Sources: ISO 3691-4:2023 on iso.org, ISO/DIS 3691-4 revision status, ISO 3691-4:2023 scope (iTeh preview), A3 on ANSI/A3 R15.08 Parts 1 and 2, Regulation (EU) 2023/1230 on machinery.
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