Autonomous driving levels explained

When the first internal combustion engines became available to the general public, their acceptance was slow-going. The path of progress is often misunderstood.

Similarly, autonomous vehicles of the modern era are also viewed with hesitance. While there are many levels of autonomous driving, most “self-driving” cars on the road today aren't considered fully autonomous but rather "semi-autonomous." More technically speaking, they have Level 2 or 3 autonomy.

Many automotive companies are competing to be the first with a Level 5 "fully autonomous" car, but we may never actually see a company achieve it.

The 6 levels of vehicle autonomy

The Society of Automotive Engineers (SAE) defines the levels of vehicle autonomy as follows:

Level 0: The vehicle has zero computer-assisted driving technology. In short, all automobiles made before the mid-1990s were Level 0 autonomous.

Level 1: The vehicle has either braking/acceleration assistance or steering assistance. A Level 1 autonomous vehicle could have either adaptive cruise control or lane-centering steering assistance, but not both.

Level 2: The vehicle has braking/acceleration assistance and steering assistance. A Level 2 autonomous vehicle could have adaptive cruise control and lane-centering steering assistance.

Level 3: When the autonomous feature is turned on, the vehicle is no longer primarily piloted by a human driver. Level 3 autonomous features can fully pilot the vehicle, but only in qualifying conditions like sitting in traffic or driving down a highway. When acceptable driving conditions aren't met, the car will request that a human take over driving.

Level 4: Level 4 autonomous features can fully pilot the vehicle and will not request that a human take over driving the car. The human driver still has the ability to manually override the computer.

Level 5: Level 5 autonomous vehicles are fully piloted by a computer and can operate in all conditions, anywhere.

For Levels 0-2, the vehicle is still piloted by a human driver. The autonomous vehicle feature is merely assisting them, and the vehicle is under constant supervision of the driver. The critical distinction for autonomy Levels 3-5 is that the car is not being piloted by a human when the autonomous driving features are engaged.

To learn more about what autonomy levels vehicles have today, check out our article, 5 Levels of Autonomous Driving Technology.

What is a level 5 autonomous car?

Level 5 autonomous cars can drive in all driving conditions, anywhere. This implies that autonomous cars are able to drive in the middle of a blizzard at night in a remote place without cellular service.

While this may be possible in theory, we must ask ourselves if it's even necessary. Is Level 4 autonomy all we need as a civilization? A vehicle with Level 4 autonomy features would be able to drive in most conditions and will never require a human to take control of driving the car.

In reality, humans prefer to only drive in favorable conditions; for example, if it snows 5 feet (152 cm), humans generally choose not to drive and stay inside where it's safe. Level 4 autonomous vehicles would be required to do the same.

If the driving conditions are deemed unsafe, a Level 4 autonomous vehicle would simply not pilot the car until the driving conditions improve. For this reason, perhaps Level 4 autonomous vehicles are all modern society needs.

If a professional driver with lightning-speed reflexes deems driving conditions unsafe, should the road even be driven?

Is level 5 vehicle autonomy necessary?

Of course, a vehicle that can safely drive in any and all conditions may be valuable. But a Level 4 autonomous vehicle is sufficient for the vast majority of everyday drivers. Ultimately, this should come as good news, as some companies claim they're nearing Level 4 autonomy very soon.

In an interview with podcaster Lex Fridman in December 2021, Tesla CEO Elon Musk said Tesla would achieve Level 4 autonomy "next year," given that they already sell Level 3 autonomous cars. Learn more about how Tesla is building an engine to achieve next-level autonomy.

If this feat is achieved, Level 4 autonomous cars may truly revolutionize personal transportation and increase road safety, even for those not driving in autonomous vehicles. Incredible progress has been made on the technology used for all autonomous vehicle levels. Still, we may never see Level 5 autonomous cars on the road, as they may never really be needed.

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