What does "self-driving" mean, exactly? Well, it depends!
SAE International, formerly known as the Society of Automotive Engineers, created guidelines for assessing automated driving features, ranging from Level 0 (no driving automation) to Level 5 (full automation).
The SAE guidelines have their critics. The terminology can be vague and confusing. The technological leap from Level 2 upward is not as linear as the guidelines suggest. Some car manufacturers have found Level 2 to be too broad and have begun referring to their cutting-edge systems as "Level 2-plus."
But nonetheless, the SAE guidelines are the broadly accepted rubric for discussing the road to full self-driving.
Here's a breakdown of SAE Levels 0-5.
Level 0 (No driving automation)
Level 0 is straightforward. The human performs all driving tasks. The car does not take over any aspect of driving. Driver assistance features like blind-sport warnings or lane departure warnings would qualify as Level 0.
Availability: On virtually every vehicle
Level 1 (Driver Assistance)
Level 1 driver assistants have the car control one aspect of the driving — either the steering or the speed. Cruise control and lane centering are prominent examples.
Availability: Most new cars
Level 2 (Partial Driving Automation)
Level 2 systems like Tesla’s Autopilot or GM’s Super Cruise control both the steering and speed and operate mostly on mapped highways. They may be hands-free and incorporate features like automatic lane changes but Level 2 systems still require complete driver attention at all times.
Availability: Some new high-end cars
Level 3 (Conditional Driving Automation)
Level 3 is the first level the SAE considers automated driving. The driver is not driving the vehicle while the system is engaged under certain conditions. The driver must still be ready to take over if the system disengages. Mercedes’s Drive Pilot is the first Level 3 system to be approved for road use in Nevada. It’s a traffic jam assist where the vehicle can drive itself! On congested highways. Below 37 mph.
Availability: Only Mercedes and only in Nevada.
Level 4 (High Driving Automation)
The driver is no longer needed at Level 4 self-driving. The vehicle may have a steering wheel and pedals for human operation but is not required to. Level 4 systems operate autonomously within a specific “geofenced area.” The vehicle is programmed to disengage and come to a stop on its own if there’s a problem. Examples could include driverless buses and taxis in a city center.
Availability: Undergoing testing in certain locations
Level 5 (Full Driving Automation)
Level 5 is full-self driving. Like Level 4, no human involvement is required beyond setting a destination. But unlike Level 4, the vehicle can operate autonomously in all locations and under all conditions. This is the full self-driving dream. And as of now, it is only a dream.