(Motor Authority) – Self-driving cars are part of an uncertain future, but automakers have signaled that they are steadily heading towards a day when at least some of us won’t be driving at all.
Along the way, automakers will offer different levels of self-driving capability. What are these levels and how are they defined? We are here to help.
While levels of self-driving sophistication can vary widely between brands, the defined limits of those levels are relatively fixed.
In 2014, the Society of Automotive Engineers adopted a common taxonomy for self-driving cars that defined six levels, from level 0 to level 5, of automated driving. The limitations are quite obvious. Level 0 was unassisted and Level 5 was fully self-contained. SAE updated its levels in 2021, and while Level 5 remains entirely self-contained, Level 0 has changed to include some active safety features that have become in recent years.
It’s important to note that automakers have described some self-driving features as “fully autonomous” or “Level 5” (notably Tesla), but fully autonomous cars are banned from virtually all roads in the United States. States, and the terms and levels are not interchangeable. Most car self-driving functions hover around level 2 or level 3, but the road to levels 4 and 5 remains unclear. Fully self-driving, Level 5 cars are at least a decade away – and it’s entirely possible they won’t be initially available to consumers when they arrive, if ever.
So what do these levels mean?
Level 0: No self-driving function. Drivers are responsible for steering, throttle and braking control. They are also responsible for monitoring all around the car. Level 0 has been updated to include features that provide warnings and temporary assistance, including automatic emergency braking, blind spot monitors and lane departure warnings. The vast majority of cars on the road today fall into this category.
SAE levels of driving automation, from zero to fully autonomous
Level 1: Some driving aids are authorised. In cars equipped with level 1 automation, the car can take control of the steering Where accelerator/brake in certain situations, but it relies on the driver to take over immediately if these systems fail. Many newer cars have adaptive cruise control that can slow the car to a stop, which falls into this category. Some cars are equipped with active lane control systems (also called lane departure prevention) which allow for limited periods of driving without intervention.
Cadillac’s Super Cruise system being tested.
Level 2: More driving assistance. Level 2 automation differs from Level 1 automation in the number of systems used to assist drivers, but the two levels are identical in requiring drivers to take over immediately if these systems fail or stop working . Level 2 allows simultaneous use of adaptive cruise control and active lane control. Several automakers offer systems that will take over throttle/brake and steering control for a limited time, but require driver interaction or these systems shut down, usually with multiple warnings to the driver. (What happens when they turn off is important in distinguishing between level 2 automation and higher levels.) Some of today’s most sophisticated systems can handle all the commands at full speed on highway, but still require the driver to watch the road ahead. The best of these is GM’s Super Cruise. Ford’s Bluecruise and Tesla’s Full Self-Driving are also eligible here.
Volvo Drive Me self-driving car pilot project Gothenburg, Sweden
Level 3: Level 3 remains theoretical. It consists of conditional automation. Many automakers have said they will ignore Level 3 automation because it can be dangerous to immediately hand over all driving duties to a human who is not required to pay attention to the road. Level 3 automation can handle all driving situations in certain situations and constantly monitors the road, unlike Level 2 cars. Limited testing has shown that these systems may not be safer than no automation, but most experts stop short of saying that level 3 cars should be banned. While SAE’s chart says “traffic jam driver” qualifies for this level, no car on the road has it, even cars with systems labeled traffic jam assist. These systems, which typically handle the controls in low-speed traffic jam situations, still require the driver to monitor the system.
Level 4: Almost autonomous. Most automakers are targeting Level 4 automation for several reasons. First, it’s likely to be cheaper because Level 4 self-driving cars may not require driver controls such as a steering wheel, throttle, or brake pedals. Building a car with redundant driver controls and autonomous systems would be expensive and complicated. Second, Level 4 differs from Level 3 mainly because it does not require human intervention in the event of failure of autonomous driving systems. GM’s Cruise Automation is one of many entities that operate limited local fleets of driverless cars that fall into this category.
Level 5: Fully autonomous. It might seem like a logical small step from Level 4, but for most automakers, Level 5 autonomy is a giant leap for self-driving cars. Level 5 cars would be self-driving, anytime, anywhere. Since most roads in the country are not pencil straight highways on a sunny day, the final SAE level would require extensive testing for sensors that cannot yet read road lines in bad weather, low light , on dirt roads or countless other varying circumstances. While having a steering wheel and pedals does not prevent a car from being level 5, to earn the designation those controls would be unnecessary: level 5 cars are not driven by humans under any circumstances.
