A brief guide to the SAE Levels of Driving Automation 2021
With so many self-driving articles quoting the SAE Levels of Driving Automation, we delve into the benchmarks, and consider how they inform both the industry and the wider public.
Launched in 2014 by US-based SAE International, formerly the Society of Automotive Engineers, the document in question is SAE J3016 Recommended Practice: Taxonomy and Definitions for Terms Related to Driving Automation Systems for On-Road Motor Vehicles.
The most recent version, published in May 2021, uses a six-level scale ranging from zero, “no driving automation”, up to five, “full driving automation”.
We’ll dig deeper into that in a moment, but it is important to note that most people get no further than the headline graphic. This oft-shared image sets out the responsibilities of “the human in the driver’s seat” at each level.
Levels of automation
For levels 0-2, it says: “You are driving whenever these driver support features are engaged – even if your feet are off the pedals and you are not steering” and “You must constantly supervise these support features; you must steer, brake or accelerate as needed to maintain safety”. Basically, you’re still a driver.
Expectations for levels 4-5 are straightforward enough too: “You are not driving when these automated driving features are engaged – even if you are seated in the driver’s seat” and “These automated driving features will not require you to take over driving”. Basically, you’re now a passenger.
Which leaves Level 3, and the instruction: “When the feature requests, you must drive”, applicable to features such as “traffic jam chauffeur”. This is the most controversial part of the guidance, with some experts vehemently opposed to systems which rely on the handing over and/or retaking of control.
Earlier this year, Bill Gates, noted: “Right now, we’re close to the tipping point – between levels 2 and 3 – when cars are becoming available that allow the driver to take their hands off the wheel and let the system drive in certain circumstances. The first Level 3 car was recently approved for use in the United States, although only in very specific conditions.”
That was Mercedes’ Drive Pilot, available on 2024 S-Class and EQS Sedan models. “Certification in Nevada marks the start of its international rollout and, with it, the dawning of a new era,” said Mercedes-Benz CTO, Markus Schäfer.
On this side of the pond, in April, The Department for Transport approved the use of Ford’s BlueCruise system on parts of our motorway network – the first time any UK driver can legally take their hands off the wheel. Ford, Government ministers, Thatcham, and others, emphasised it is Level 2 driver assistance, but that didn’t stop the media from misleadingly describing it as self-driving.
Expert comment
And here’s the crux. As Professor Nick Reed, of Reed Mobility, told the Transport Select Committee recently, the SAE levels “…work from an engineering perspective, but they don’t work very well from a communications perspective.” That’s not a criticism of the SAE, which describes itself as a “standards developing organization for engineering professionals”.
David Wong, senior technology manager at The Society of Motor Manufacturers and Traders (SMMT), told the Committee: “A self-driving vehicle is a vehicle that’s fitted with an automated driving system capable of performing the entire dynamic driving tasks without human intervention within an Operational Design Domain (ODD).”
The ODD differentiates level 4 from 5, with BSI’s CAM vocabulary telling us this can include environmental factors, time-of-day restrictions, and road characteristics. At Level 5, automated systems “can drive the vehicle under all conditions”.
In world-leading testing, Level 4 buses are currently being trialled on UK public roads, with a safety driver. For example, by First Bus at Milton Park, and Stagecoach’s CAVForth. Last year, Oxa (previously Oxbotica), said its zero-occupancy trial was facilitated by a new kind of insurance. That’s telling. For car manufacturers, the leap to Level 4 is now as much about regulation as it is technology.
Please note: a version of this article was first published in the Institute of the Motor Industry’s MotorPro magazine.