What are the different levels of self-driving cars?

In many ways self-driving cars are an eventuality and a reality.

As automakers approach full autonomy, several new cars now boast self-driving features that inch toward the goal of driver-less cars soon. Limited hands-free driving systems on the market now are GM’s Super Cruise, Tesla’s Autopilot, Ford’s Bluecruise, and many other ones in various stages of development. 

Many of these features can be grouped together in a uniform set of self-driving “levels,” which were defined by the Society of Automotive Engineers in 2014 and last updated in 2021.

Although many new car buyers don’t—or won’t—need to know what each level specifically means, it may be helpful to understand the basic principals to understand what system could be right—and what systems may not be allowed by law in their area.

MORE: GM’s Super Cruise sails past Ford’s Bluecruise

Here’s our primer on the SAE-accepted levels, what they mean for new cars, and some examples of systems on the road that would fall into these categories.

(Note: Although automakers tout “fully autonomous” or “Level 5” self-driving cars, those types of cars are outlawed on virtually every public road in America, and in some cases the term may be used by manufacturers or representatives incorrectly.)

SAE levels of driving automation, from none to fully self-driving

Level 0: No self-driving features, but it can have driver support systems.  Many cars on the road today would fall into this category—even when they’re equipped with safety systems such as automatic emergency braking or blind-spot monitors. Automatic emergency braking detects imminent impact and hits the brakes to mitigate or avoid the impacts of a crash. The majority of automakers complied with a voluntary pledge by Sept. 2022 to equip 95% of the cars they produce with this life-saving feature that the IIHS predicts will cut in half the number of rear-end crashes, which is the most common crash. The SAE updated this classification in 2021 to reflect the evolution of new car technology. Level 0 previously relied solely on the person behind the wheel to control the car’s functions, including steering, throttle, and brake, while the car is running.

Automatic Emergency Braking graphic

Level 1: Some driver assistance. By the book, these cars may have one or more systems that can control speed or steering—but not both simultaneously. Many new cars have available adaptive cruise control, which is an example of a Level 1 feature. Active lane control that keeps the car centered in its lane is another example.

Level 2: Even more driver assistance. Many luxury automakers are now making available Level 2 cars that can control steering and speed simultaneously, without driver interaction for short periods of time (under 1 minute, and in some cases seconds). For now, Volvo, Mercedes-Benz, and BMW all offer Level 2 features, but all three systems require a driver monitor the environment around the car. The most sophisticated is GM’s Super Cruise, thought Tesla’s Autopilot garners a lot more headlines, for better or worse. Along with Ford’s Bluecruise, these systems can drive on mapped highways for extended periods with driver supervision, and, except for Tesla, they have driver monitor cameras to ensure driver engagement.  

GM Super Cruise warning alert graphic

Level 3: Conditional autonomy. Tesla touted its Autopilot as such for being able to drive on streets and highways in stop-and-go situations, but it’s not. Unlike Level 2 cars, Level 3 autonomy can control a car in all situations and the car is constantly monitoring the road, but unlike higher levels on the SAE scale, Level 3 cars will return to human control if the system can’t function correctly. According to the SAE definition, Level 3 cars will ask drivers to intervene when the self-driving systems fail, but for many automakers that presents a safety problem for drivers who rely too much on the systems and may not be prepared to take over.

Tesla Model S owner tests Autopilot system from back seat

Level 4: Nearly autonomous. As a Level 4 car, no driver interaction is needed and the car will stop itself if the systems fail, which is an important distinction from Level 3. Automakers such as GM, Mercedes-Benz, and Tesla have already implemented systems that will slow self-driving cars to a stop and engage hazard lights if the driver doesn’t interact with the car. Does this mean you can’t drive a Level 4 car? Not necessarily. But automakers have already indicated that including self-driving features and driver-operated controls (steering wheel, gas pedal, brake pedal) is redundant and costly. Volvo has said it will make a Level 4 XC90 that includes both driver controls and self-driving autonomy, but they’re the only one so far. There are many prototypes and concepts intended as driverless shuttles. 

Zeekr shuttle for Waymo self-driving service

Level 5: Completely autonomous. The holy grail of self-driving cars might be just as hard to find. Although Level 4 to Level 5 may seem like a small step, in reality it’s a giant leap. Level 5 autonomy takes the driver all the way out of the equation. While the presence of a steering wheel, gas and brake pedals don’t preclude a car from being Level 5, they’d be useless: These cars are not supposed to be driven by people. Getting cars to read roads without clear lines, during bad weather, or in variable conditions is a huge undertaking for sensors and computing power and not likely to be done any time soon. No automaker or startup has laid out a firm timeline for Level 5 cars to hit the road, but many have said that it’s at least a decade or longer away. That’s assuming that they’re even available to the public and legal, which is still unclear.