In many ways self-driving cars are an eventuality and a reality.
As automakers approach full autonomy toward the end of this decade, several new cars now boast self-driving features that inch toward the goal of driver-less cars soon.
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.
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.
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 autonomy
SAE levels of autonomyEnlarge Photo
Level 0: No self-driving features. Many cars on the road today would fall into this category—even when they're equipped with forward collision warning or blind-spot monitors. Level 0 relies solely on the person behind the wheel to control the car's functions, including steering, throttle, and brake, while the car is running.
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. By 2021, an overwhelming majority of new cars sold in the U.S. will feature automatic emergency braking, which is also a Level 1 feature. Additionally, automakers such as Subaru are now making available active lane control on entry-level cars, which can steer a car back into a lane, but those systems aren't as prevalent as adaptive cruise control.