What are all these autonomous car levels?

Source: Dllu via Wikipedia CC BY-SA 4.0

With increasing demands for automation, autonomous cars will inevitably clog the road system in the next few decades. Marques such as Audi and Tesla have rolled out their respective self-driving machines, which had been labelled as Traffic Jam Pilot for the former and Autopilot for the latter.

If you've been following the development of autonomous cars, you will surely have come across phrases such as Level 2, 3 and 4 autonomous levels. What do these categories tell the consumers?

Autonomous Levels

In a bid to dispel confusion over a car's level of self-driving capability, SAE International has drawn up its standard in categorising driving automation of on-road vehicles.

In SAE's standard, 6 levels of automation level ranging from 0-5 tells consumers the range of autonomous ability from no automation to full automation. Compiled below is the lists of defined sets of SAE standards in classifying driving automation:

Level 0: This is obviously a car that requires a driver's full control at all times, the kind of cars we're all familiar with and learn to drive in. Drivers are responsible for handling every aspects of driving dynamics, even when equipped with warning systems. Say your car has reverse sensor fitted. It merely warns you audibly you're reversing into an obstacle but the onus is entirely on you to avert collision. The car won't save you if you bungle.

Level 1: Assistance from driver assist systems that either automates steering or acceleration/deceleration aspects, but not both simultaneously, using information about the driving environment. Drivers are still responsible for handling all remaining aspects of driving dynamics. Cars equipped with, but not limited to, adaptive cruise control and lane keep assist fall in this level.

Level 2: This basically means a car can handle both steering and acceleration/deceleration aspects simultaneously. These cars have the ability to stay within lane marking and even apply the brakes for you. However, this only works in certain conditions and drivers still need to remain fully alert. 

Level 3: Conditional automation to use SAE International's terminology. Drivers can hand over control fully to the car, but must be prepared to take control when requested by the car once the factors enabling it to function ceases. As an example, Audi's Traffic Jam Pilot, introduced on the A8, only works during nose-to-tail traffic congestion, at speed of 60 kph (37 mph) and below, and presence of physical barrier separating opposite lane. As long these conditions are met, drivers can relax and let the car handle the rest. Outside the stipulated conditions and the driver must resume responsibility.

Level 4: Ahh the gate towards full automation. In this level, driving dynamics is handled by the car in most conditions. Whether drivers are still required to take the wheel if the car exceeds its operational design domain or the car can automatically stop if drivers fail to interact is up for debate. Some publications, such as Clean Technica and The Drive, believe it's the former, while Autoweek and The Washington Post believe in the latter notion. I would agree with Clean Technica and The Drive viewpoint as it wouldn't be Level 4 if the car can handle everything independent from the driver, which segues to the next and final category of driving automation.

Level 5: Well, to sum this level up, "Dude, your car can drive itself. Throw the steering and pedals away!". Yeah, the car can handle itself in all conditions without needing any help from the drivers. Just get your ass in the car, tell it where to go and whatsapp your GF while the car speeds down the freeway by itself.