Automated driving is usually described with the six levels of SAE J3016, but those levels are an engineering vocabulary, not a legal test. A fleet buyer, product manager or insurer who treats “Level 3” as a statement of what the law allows will draw the wrong conclusion about who is responsible when the system is engaged.
This explainer sets out what each SAE level means, the terms that sit underneath them (the dynamic driving task, the operational design domain and fallback), how UN Regulation No. 157 approves one type of system, and how Great Britain’s Automated Vehicles Act 2024 sorts vehicles into categories of its own. Status is given as of November 2026.
The vocabulary behind SAE J3016
SAE J3016 is a recommended practice published by SAE International. Its current edition, J3016_202104, was announced on 3 May 2021 after work with ISO’s intelligent transport systems committee, and SAE’s release said the underlying taxonomy was unchanged from the 2019 version. The levels rest on a few defined terms, summarised in ANSI’s overview of J3016:
- Dynamic driving task (DDT): the real-time operational and tactical functions needed to drive in traffic, including steering, speed control and object and event detection and response.
- Operational design domain (ODD): the specific conditions under which a feature is designed to work, such as road type, speed range, weather or time of day.
- Fallback: what happens when the feature can no longer continue, either a human taking over or the system bringing the vehicle to a minimal risk condition.
The 2021 edition also groups Levels 1 and 2 as driver support features and Levels 3 to 5 as automated driving systems, and it excludes warning and momentary intervention systems from the levels altogether. For how to turn an ODD into something a supplier can be held to, see our guide to making the operational design domain a working contract.
Automated driving levels 0 to 5 compared
| Level | Name | Who performs the DDT | Human role |
|---|---|---|---|
| 0 | No driving automation | Human | Drives at all times |
| 1 | Driver assistance | Human, with steering or speed support | Drives and supervises |
| 2 | Partial driving automation | Human, with steering and speed support | Supervises constantly and responds to events |
| 3 | Conditional driving automation | System, within its ODD | Must be ready to take over when asked |
| 4 | High driving automation | System, within its ODD | Not expected to take over |
| 5 | Full driving automation | System, without an ODD limit | Not expected to take over |
The practical dividing line sits between Levels 2 and 3. At Level 2 the person in the seat is still driving, because they must monitor the road and respond. At Level 3 the system performs the whole driving task within its ODD, and the person becomes what SAE calls a fallback-ready user. Level 4 removes the expectation that a human will respond at all, but only inside a defined domain; Level 5 removes the domain limit.
ALKS and UN R157: approving automated driving on motorways
Levels describe capability; type approval decides whether a specific system can be sold. UN Regulation No. 157 on Automated Lane Keeping Systems, published in the EU’s Official Journal on 9 March 2021 and in force from 22 January 2021 according to the EUR-Lex text, was the first binding international rule for this kind of system. As originally adopted it covered passenger cars at up to 60 km/h. Its main safeguards include:
- a driver availability recognition system that checks the driver can resume control;
- a transition demand, the structured request for the driver to take back the driving task, with time allowed for a safe handover;
- a minimum risk manoeuvre, which the system carries out if the driver does not respond or a severe failure occurs;
- a data storage system for automated driving that records events.
UNECE announced an amendment that raised the maximum speed to up to 130 km/h on motorways, allowed system-initiated lane changes and required those lane changes to be recorded, entering into force in January 2023 for contracting parties that apply it. An R157 approval is evidence about a defined system, not a legal classification on its own; our article on why a standard reference does not settle the legal question explains the distinction.
How UK law categorises automated driving
British law does not use SAE levels as legal categories. The Law Commissions’ joint report of 26 January 2022 recommended a self-driving test written into law, with a bright line separating it from driver support features. The Automated Vehicles Act 2024, which received Royal Assent on 20 May 2024, adopts that approach.
- Self-driving test: under section 1, a vehicle meets the test if a feature lets it travel autonomously, safely and legally. Autonomously means controlled by the vehicle’s equipment with no individual monitoring it for immediate intervention.
- User-in-charge features: the explanatory notes describe features that drive for part of a journey, such as a motorway chauffeur, with a person present to drive the rest. Under section 46 that person is the user-in-charge while the feature is engaged.
- No-user-in-charge features: features that drive for a whole journey, such as an airport shuttle, overseen by a licensed operator. Section 53 creates an offence of using a vehicle with no one in control unless such a feature and operator are in place.
- Immunity: the explanatory notes state that a user-in-charge is not liable for offences arising from how the vehicle drives itself, but that protection ends if they fail to respond to a valid transition demand.
Anything that does not meet the self-driving test remains driver assistance in law, and the human remains the driver. That covers every Level 2 system, whatever its marketing name.
Status of UK automated driving rules in November 2026
Most of the 2024 Act is not yet in force. Legislation.gov.uk marks sections 1 and 46 as prospective. Under the earlier Automated and Electric Vehicles Act 2018, section 1 requires the Secretary of State to list vehicles that can safely drive themselves, but the GOV.UK list states that no self-driving vehicles are listed. The government’s implementation programme says the Act is being implemented in 2027. Recent steps include:
- 22 May 2026: applications opened for the automated passenger services pilot for taxi and bus-style services.
- 17 June 2026: consultation on a draft statement of safety principles, which closed on 9 September 2026.
- 1 July 2026: SI 2026/731 was made, bringing the marketing restrictions in Part 4, including section 78, fully into force on 7 January 2027.
When the government announced Royal Assent on 20 May 2024, it said vehicles would need to be at least as safe as careful and competent human drivers.
Key points for fleet and product teams
- SAE levels describe how driving is shared; they do not decide liability in Great Britain.
- Levels 0 to 2 are driver support: the human is driving and responsible.
- At Level 3 and above the ODD and the fallback arrangements determine what the system can be trusted to do.
- UN R157 approves a specific motorway system with defined handover and minimum risk behaviour.
- UK law uses the self-driving test and the user-in-charge and no-user-in-charge categories; most of those provisions await commencement.
- Test supplier claims against the approval and the ODD, as our guide to ADAS scenario test coverage describes.
This article is general information, not tax, legal or financial advice.
Sources
- SAE International via PRWeb: SAE International and ISO collaborate to update and refine SAE Levels of Driving Automation
- ANSI Blog: SAE Levels of Driving Automation, J3016 2021
- EUR-Lex: UN Regulation No 157, Automated Lane Keeping Systems
- UNECE: UN Regulation extends automated driving up to 130 km/h in certain conditions
- Law Commission: Automated vehicles project
- legislation.gov.uk: Automated Vehicles Act 2024
- legislation.gov.uk: Automated Vehicles Act 2024, section 1
- legislation.gov.uk: Automated Vehicles Act 2024, section 46
- legislation.gov.uk: Automated Vehicles Act 2024, section 53
- legislation.gov.uk: Automated Vehicles Act 2024, section 78
- legislation.gov.uk: Automated Vehicles Act 2024 explanatory notes, commentary
- legislation.gov.uk: The Automated Vehicles Act 2024 (Commencement No. 3) Regulations 2026
- legislation.gov.uk: Automated and Electric Vehicles Act 2018, section 1
- GOV.UK: Self-driving vehicles listed for use in Great Britain
- GOV.UK: Automated Vehicles Act implementation programme
- GOV.UK: Passengers one step closer to booking taxi and bus-style self-driving vehicles
- GOV.UK: Public invited to have their say on self-driving vehicle safety
- GOV.UK: Self-driving vehicles set to be on roads by 2026 as Automated Vehicles Act becomes law
Sources checked in November 2026. Rules, rates and schemes can change after publication, so check the linked official pages before acting.
