Self-driving cars: A level-by-level explainer of autonomous vehicles

Your guide to understanding the road to self-driving vehicles, as defined by the Society of Automotive Engineers.

Kyle Hyatt Former news and features editor
Kyle Hyatt (he/him/his) hails originally from the Pacific Northwest, but has long called Los Angeles home. He's had a lifelong obsession with cars and motorcycles (both old and new).
Chris Paukert Former executive editor / Cars
Following stints in TV news production and as a record company publicist, Chris spent most of his career in automotive publishing. Mentored by Automobile Magazine founder David E. Davis Jr., Paukert succeeded Davis as editor-in-chief of Winding Road, a pioneering e-mag, before serving as Autoblog's executive editor from 2008 to 2015. Chris is a Webby and Telly award-winning video producer and has served on the jury of the North American Car and Truck of the Year awards. He joined the CNET team in 2015, bringing a small cache of odd, underappreciated cars with him.
Kyle Hyatt
Chris Paukert
5 min read
General Motors

Here at Roadshow, we spend a great deal of time covering the rapidly growing field of self-driving car tech. Because both today's and tomorrow's vehicles offer dramatically varying degrees of automated driving, it became necessary to develop a classification system to describe the progression of these technologies, if only to use as shorthand for understanding their relative capabilities and limitations.

SAE International (aka the Society of Automotive Engineers), a professional association that often sets industry guidelines, stepped in to provide a helpful level-by-level guide. First published in 2014, these J3016 guidelines have become the industry standard, having been adopted by both the US Department of Transportation and the United Nations.

On the road to self-driving, autonomous cars, there are six levels of automation, according to the SAE, and each level has a specific set of requirements that a vehicle must meet before it can be considered to operate at that level.

It's important to note that there's still a lot of nuance and variation of vehicle abilities even within each SAE level, a reality that has given rise to more than a bit of criticism among self-driving authorities. That said, the SAE's approach to automated driving remains the industry's most widely accepted classification system, so it's still important to know and understand these levels.

2018 Honda Fit
Enlarge Image
2018 Honda Fit

Level 0 applies to all vehicles that rely solely on humans to dictate driving actions, like this trusty and affordable 2018 Honda Fit.


Level 0: No automation

A car has no automated assistance technologies, though it may feature traditional fixed-speed cruise control hardware or warn of an impending crash (without intervening). A vehicle that fits into this category relies on a human to dictate every driving action.

Examples: Your uncle Rick's 2005 is a Level 0 vehicle.

Long-Term 2018 Kia Stinger GT
Enlarge Image
Long-Term 2018 Kia Stinger GT

The Kia Stinger GT can be had with adaptive cruise control and lane-keeping technology, which makes it a Level 1 vehicle.

Steven Ewing/Roadshow

Level 1: Driver assistance

Most modern passenger cars qualify as capable of Level 1 on the SAE scale. To meet this requirement, a vehicle must have at least one advanced driver-assistance feature -- adaptive cruise control, for instance. Mobility is still supervised by a human, but for convenience, the vehicle is capable of maintaining its own speed under certain circumstances. Lane-keeping tech also falls into this category. Pretty basic stuff.

Examples: Any model with adaptive cruise control or lane-keep technology is at least a Level 1 vehicle.

Cadillac Super Cruise
Enlarge Image
Cadillac Super Cruise

The Cadillac CT6's Super Cruise system qualifies it for Level 2 classification. 


Level 2: Partial automation

A Level 2 vehicle has two or more advanced driver assistance systems (ADAS) that can at times control the braking, steering or acceleration of the vehicle. Examples of qualifying ADAS includes adaptive cruise control, active lane-keep assist or automatic emergency braking, and these technologies must be applied in a coordinated fashion.

Such individual assist features vary in sophistication, but are increasingly common, and are available on nearly all but the most budget-minded vehicles in 2018. However, it's the coordination between two or more of these assist technologies that helps them qualify for Level 2 status.

Importantly, in a Level 2 vehicle, a human driver must still actively monitor the vehicle's progress and be ready to intervene at any time.

Examples: Super Cruise, Distronic Plus, ProPilot Assist, Autopilot.

2019 Audi A8 Traffic Jam Assist
Enlarge Image
2019 Audi A8 Traffic Jam Assist

The 2019 Audi A8 might be the first Level 3 vehicle available for public consumption. The company's Traffic Jam Pilot tech is still awaiting approval in many countries, including the US.


Level 3: Conditional automation

The jump in complexity between Levels 2 and 3 is huge compared to the jump between 1 and 2. A Level 3 vehicle is capable of taking full control and operating during select parts of a journey when certain operating conditions are met.

For example, a vehicle that is capable of managing itself on a freeway journey, excluding on- and off-ramps and city driving, might be considered Level 3 automated. This level of automation requires advanced sensor packages, hardware backups and sophisticated software to keep occupants safe.

The driver must remain vigilant, even when the vehicle is self-driving, in the event of a failure. Even with Level 3, a driver monitor system is all but a prerequisite to ensure that the person in the driver's seat is sufficiently alert to take over when conditions dictate.

Google achieved Level 3 autonomy back in 2012 with its test vehicles, but found that human drivers were too trusting and slow to retake control from the system in the event of trouble. This observation ultimately led Google to decide against taking the tech to market, so it's pursuing full Level 5 automation through its Waymo division.

Examples: Audi aims to sell the first Level 3-capable vehicle to the public, but its Audi AI Traffic Jam Pilot system in the new A8 sedan is still awaiting legal approval in many countries, including the US.

Toyota Platform 3.0 Autonomous Test Vehicle
Enlarge Image
Toyota Platform 3.0 Autonomous Test Vehicle

Toyota tests "Chauffeur" mode in its Platform 3.0 test vehicle, which is capable of Level 4 autonomy. 


Level 4: High automation

Level 4 is where things start getting a little "Minority Report," and where bona-fide autonomous driving systems kick in. A Level 4 vehicle is capable of completing an entire journey without driver intervention, even operating without a driver at all, but the vehicle does have some constraints. As an example, a Level 4 vehicle may be confined to a certain geographical area (i.e. geofenced), or it could be prohibited from operating beyond a certain speed.

A Level 4 vehicle likely still maintains driver controls like a steering wheel and pedals for those instances in which a human may be required to assume control.

Examples: There are no Level 4 production vehicles available to consumers.

Cruise AV
Enlarge Image
Cruise AV

Level 5 vehicles have no provisions for human control, like steering wheels or pedals. 

General Motors

Level 5: Full automation

Level 5 is the ultimate goal of self-driving vehicle developers. A Level 5 vehicle is capable of complete hands-off, driverless operation under all circumstances. This is the level where there are no provisions for human control -- no steering wheel, no pedals, no joysticks. A vehicle's passenger would be able to, in theory, kick up their feet and play some Fortnite, wholly unconcerned about the act of driving.

A Level 5 autonomous vehicle is unconstrained geographically and theoretically able to travel at all speeds in safety, thanks to advanced software and vehicle-to-vehicle and vehicle-to-environment communications.

General Motors has been the most vocal about pushing for a commercially viable Level 5 vehicle in the near future, with its Cruise autonomous test vehicles. However, many in the industry are concerned that GM may have developed an Icarus complex, and is a lot further from true Level 5 autonomy than it thinks.

It's hard to imagine a world where Level 5 autonomous vehicles become the norm, available to all. If that happens, how would that change the way that we live? We'd no longer need to be anywhere near as concerned with traffic or traffic safety. We'd be able to work during commutes or dispatch vehicles to run errands for us while we did something else. We might not even need to own a car at all, since they should be easy to summon from a service.

Ultimately, it will likely be a long time before Level 5 becomes a reality, if indeed it actually happens at all. But even if it takes decades for a majority of new vehicles to feature full autonomy, it's exciting to think about right now, and it's important to understand how the level-by-level ramp-up is affecting motoring life today.