Autonomous Driving Levels: What Do They Mean, Why Are They Important?

Mon, Oct 31, 2016 1,602

Believe it or not, self-driving cars are closer to science fact than science fiction. But because the technology is so novel, you most likely have some questions about them.

It seems as though every other day another automaker announces its future plans for autonomous vehicles, and many times it will mention what level of autonomy those vehicles’ systems will have. The problem, is they seldom explain what those levels actually mean.

To help you understand exactly what you’re reading the next time a manufacturer talks about their “Level Whatever” car, we broke down why there are levels of autonomy and what those levels denote.

Why we have levels of driving automation?
As is the case with any industry, the automotive industry needs general standards for any product or service. Having those sets forth a common language to use, offers guidelines so manufacturers can properly identify their products and gives lawmakers a framework off which they can base any regulation.

Before 2014, there were two separate sets of guidelines: One from the U.S. National Highway Traffic Safety Administration, and one from the German Federal Highway Research Institute. The problem was, the two were very different from each other. In fact, they didn’t even have the same number of levels of automation.

As a result, the Society of Automotive Engineers developed universal standards to be used across the entire industry. It did so by dissecting both the NHTSA’s and GFHRI’s existing ones, as well as research from European and U.S. independent road safety organizations. Then, in 2016, SAE revised its standards to ensure they are relevant with the latest industry advancements.

What are the levels of driving automation?
SAE divides driving automation into six levels — zero through five — with Level 0 being no driving automation and Level 5 being full driving automation. Contrary to popular belief, however, these levels measure the functionality of a vehicle’s systems, rather than of the vehicle itself.

Each level is based on how much of the dynamic driving task (DDT) — steering, accelerating, braking, monitoring the surrounding environment, execution of an appropriate response to a given scenario, planning of vehicle maneuvers and using lights/indicators when required — the system can perform for a sustained period of time. This means features such as collision avoidance braking are not classified as autonomous vehicle systems because they only momentarily intervene. The autonomous program for Levels 3 through 5 is referred to as an automated driving system (ADS), meaning it can perform at least part of the DDT for a sustained period.

We broke down and simplified each level of the SAE’s guidelines, which you can read below.

Level 0: No driving automation

–Driver completes DDT at all times.
–Level 0 may have warning systems, but they don’t intervene or offer sustained support.

Level 1: Driver assistance
–Automation system performs part of the DDT — acceleration/deceleration OR steering — and disengages upon driver’s request.
–Driver must supervise at all times and perform remainder of DDT.
–Example: Radar-guided cruise control.

Level 2: Partial driving automation
–Automation system performs part of the DDT — acceleration/deceleration AND steering — and disengages upon drivers request.
–Diver must supervise at all times and perform remainder of DDT.
–Example: Radar-guided cruise control with lane-keep assist.

Level 3: Conditional driving automation
–Driving system performs entire DDT within its given operational design domain (ODD), which could be within a specific geographic location, under a certain speed, on a certain type of road, only in daylight etc.
–User must be ready to respond to a request to intervene in the event of an automated driving system failure or if the automated system will soon exceed its parameters.
–User must also be ready to intervene in case there is a mechanical failure.

Level 4: High driving automation
–Autonomous program performs entire DDT for sustained period of time within a given situation.
–No expectation for the user to intervene. If the user doesn’t respond to system’s request to intervene, the system is capable of navigating to a “minimal risk condition,” such as pulling off to the side of the road.
–Example: Tesla’s current Autopilot software.

Level 5: Full driving automation
–Driver decides when to engage the autonomous system. Once engaged, the system performs the entire DDT under any driver-manageable conditions — it couldn’t, for example, drive in a white-out snow storm — without any expectation that the user will respond to a request to intervene.
–User may perform DDT, if they so choose, by disengaging the automated driving system.
–Example: Tesla’s proposed Enhanced Autopilot software.

Photo via Daimler AG