Driverless cars remain a rare novelty, but it might surprise motorists to discover that much of the technology that will make them work is already available in the new cars they’re buying today.

In setting out recommendations for a new driverless-vehicle policy, the National Highway Traffic Safety Administration listed four levels of automation:

Level One: “Function-Specific Automation.” This includes technology that enables a vehicle to assume control of a critical function like steering, braking or the throttle. These have become more common in recent years as companies have rolled out options like adaptive cruise control, which can automatically increase or decrease speed based on traffic. Electronic stability control, which helps keep drivers in a straight line by adjusting steering in a slipping situation, is now mandatory for new vehicles sold in the U.S.

Level Two : “Combined Function Automation.” This includes technologies that combine automation on two or more critical functions but still rely on the motorist to actually do the driving and pay full attention to the road. While the NHTSA says it is just starting to work on evaluating the potential safety benefits of such technology, automakers are already pushing ahead with development, adding new offerings that, for example, help drivers keep their cars centered in highway lanes while cruise control is activated.

Levels Three and Four: “Limited Self-Driving Automation” and “Full Self-Driving Automation.” Designers are still working on perfecting technology that will allow automated cars to adapt to the many unexpected hazards of real-life driving. That’s the big difference between these two levels — Level Three technology means a car can drive itself under ideal circumstances but would have to revert to “manual mode” when encountering such conditions as construction zones. Level Four vehicles would truly offer a “sit back and relax” experience.

NHTSA says it expects to begin research into safety of these levels of technology as they’re further developed with already-in-use offerings from the lower tiers.