What is Level 2 Autonomous Driving?


If level 1 of autonomous driving can be thought of as “driver assistance,” then level can be referred to as “partial driving automation.”

At level 2, the car’s systems offer the human driver sustained assistance in both controlling the cars steering and acceleration and braking — simultaneously.

Take a minute to consider the sentence above. The car itself decides how it moves both forward and backward and from side-to-side in space.

It’s easy to think that level 2 out of 5 is nothing to get excited about, but cars that operate at this level are actually quite impressive. Yes, we’re all looking forward to a time when a car arrives on its own to pick us up, takes care of every aspect of the ride itself, drops us off at our destination, and then speeds away on its own, but that shouldn’t stop us from marveling at what level 2 cars can do on the road today.

Obviously, this is relative. To some, power steering, power windows, power anything was a huge breakthrough in their driving experience. To others, those capabilities arrived in cars without much notice. In 2019, an even larger group of drivers have never driven a car without those now-standard features, but that doesn’t mean they should be glossed over. Level 2 autonomy is no different. And, because it’s so new, I don’t think it’s in danger of being overlooked. (At least I hope we haven’t collectively lost that sense of childlike wonder.)

Importantly, in level 2, the human driver is still responsible for monitoring the environment at all times, even if she is not physically manipulating the controls in any way. In fact, the human driver is still responsible for all other aspects of the dynamic driving task (DDT). This is especially crucial as is relates to DDT-fallback.

What is DDT-fallback?

When putting together the hierarchy of driving autonomy, SAE International recognized that there will be moments when a vehicle’s systems fail to do what they’re supposed to do. This happens in two ways:

  1. The car’s systems are attempting to perform the DDT but are unable to for some reason. (An example would be if a lane-centering system is unable to perceive the lane lines because the road is snow-covered.)
  2. The car leaves the zone where it is meant to operate. (A car that is only meant to drive itself on the highway, for example, might make its way onto side streets, which would necessitate a fallback.)

How the DDT-fallback is handled is one of the major delineating factors between levels of automation from 2 to 5.

So, the DDT-fallback is the plan for what happens when something goes wrong in order to minimize the possibility of a crash.

In both of the cases list above, the DDT-fallback in a level 2 vehicle would be for the human driver to take over. For example #1, the human driver would resume the task of centering the car in the lane. For example #2, the human driver would also resume the part of the DDT which the car can no longer accomplish because it’s operating outside of its intended domain. See ODD in the article on level 1 automation for more about this.

What are some systems available today that represent level 2 automation?

I’ll list some current systems below along with some current models that include those systems. Of course, the names of these technologies will evolve, and they will also become more widely available in additional models soon, so links are provided for full context.

  • Acura’s AcuraWatch
    Acura uses Traffic Jam Assist to employ Adaptive Cruise Control (ACC) along with its Lane Keeping Assist System (LKAS). The system is able to come to a complete stop at low speeds. Models that currently have Traffic Jam Assist include the RLX and RLX Sport Hybrid.
  • Audi’s Traffic Jam Assist
    Note: This is supposedly available on the Audi A8, but the webpage link is currently broken, so I couldn’t verify it.
  • BMW’s Extended Traffic Jam Assistant
    BMW states that both Extended Traffic Jam Assistant and their remote-controlled parking function represent level 2. The latter allows a car to pull into a parking spot without the need for a human driver to intervene at all.
  • Ford’s Co-Pilot 360 Assist+
    Ford uses ACC with Stop-and-Go along with Evasive Steering Assist to accomplish level 2. You could argue that this doesn’t meet the criterion of being a sustained driving feature, but it feels borderline, so I’ve included it here. Co-Pilot Assist 360 Assist+ is available on the Ford Edge.
  • General Motors’ (Cadillac) Super Cruise
    The most advanced version of this technology is available on the 2019 Cadillac CT6. It is also noteworthy that this technology works at highway speeds (whereas many others are only available at lower speeds). That said, it is also only meant to operate on certain mapped highways and can be enabled only when the systems recognize that you’ve entered an approved zone.
  • Honda Sensing
    The Honda Sensing suite includes ACC and LKAS on several models. Vehicles that can be equipped with both include the Accord, Civic, Clarity, CR-V, Insight, Odyssey, and Passport.
  • Hyundai’s SmartSense
    The Hyundai NEXO is a dedicated hydrogen fuel cell electric vehicle and has Smart Cruise Control with Stop-and-Go along with Lane Following Assist.
  • Infiniti’s ProPILOT Assist
    ProPILOT assist uses Advanced Intelligent Cruise Control and Lane Keep Assist to achieve level 2. These are available in combination on the QX50.
  • Lexus’ Safety System+ 2.0
    Lexus combines Dynamic Radar Cruise Control and Lane Tracing Assist for level 2 automation. These are available on LS, ES, and UX models.
  • Lincoln’s Co-Pilot 360 Plus
    ACC with Stop-and-Go along with lane centering in the Lincoln Nautilus.
  • Maserati’s Highway Assist System
    The system combines ACC with Stop-and-Go and LKA. Available on the Ghibli, Levante, and Quattroporte.
  • Mercedes-Benz’s Drive Pilot
    Drive Pilot combines Active Distance Assist DISTRONIC PLUS and Active Steering Assist to achieve level 2 automation. Active Parking Assist also qualifies as level 2 automation. These features are currently available on CLA-Class vehicles.
  • Nissan’s ProPILOT
    Nissan’s ProPILOT Assist, which is part of Nissan Intelligent Mobility, represents the company’s level 2 offering. Current vehicles that are equipped with this technology include the Rogue, Rogue Sport, Leaf, and Altima.
  • Tesla’s Autopilot
    Tesla’s Autopilot is actually broken down into “Autopilot” and “Full Self Driving Capability.” The latter is a bit of a misnomer, but the available features are impressive. Autopilot includes Autosteer and Traffic-Aware Cruise Control. You can read more about the features that fall under “Full Self Driving Capability” via the Autopilot link above, but they include:
    • Navigate on Autopilot (Beta)
    • Auto Lane Change
    • Autopark
    • Summon
    • Smart Summon
  • Porsche’s InnoDrive
    InnoDrive use ACC and Active Lane Keep to achieve level 2. These are available on the Cayenne.
  • Toyota’s Safety Sense 2.0
    The system combines Full-Speed Range Dynamic Radar Cruise Control with Lane Tracing Assist. This seems to be available on the RAV4 and Corolla, but it’s worth checking on any model that has “2.0” after “Safety Sense.”
  • Volvo’s Pilot Assist
    Pilot Assist handles lane-centering/steering in conjunction with ACC to achieve level 2. Active Park Assist could also be considered level 2. These features are available on many new models.

It’s worth noting that most of the technologies above require the car’s systems to sense hands on the steering wheel, even though the human driver is not actually steering. This is to help ensure that the human driver is still paying attention to what the car is doing and the environment, since that responsibility still falls to the human in level 2.

So far, BMW’s Extended Traffic Jam Assistant and Cadillac’s Super Cruise are the only level 2 systems that will operate with “hands-free” steering. In both cases, those systems use other technology to make sure that the human driver is paying attention. BMW and Cadillac models use a driver-facing camera to track the driver’s eyes to accomplish this. Cadillac specifically names this technology the “Driver Attention Camera system.”

Why do I keep hearing about Level 2+?

Level 2+ is an intermediary stage that is used (and will start to be used more) to signal that level 2 cars will have expanded capabilities, while not yet achieving level 3 status.

While level 2 cars are aware of what’s happening in front of them, level 2+ cars are better at perceiving everything that is around the car on all sides. Some more advanced versions of driver monitoring are also branded as level 2+ (using a driver-facing camera rather than detection of hands on the steering wheel, for example.) Like any terminology, how helpful level 2+ actually is will likely determine its usage moving forward.

What would push a car to level 3 driving autonomy?

There is a very clear delineation between level 2 and level 3 cars. Cars with level 3 automation perform the entire dynamic driving task (DDT) themselves.

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