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You might have heard of Tesla ’s active driving assistance suite, known as Autopilot , that can control the car’s steering and speed to assist the driver. What you might not know, however, is that most mainstream automakers now offer similar systems on their cars, and it’s quite likely that the next new vehicle you buy will be equipped with one.
To be clear, active driving assistance doesn’t make a car “self-driving,” but rather it’s intended to support the driver—a well-designed system can help relieve driver fatigue and stress, such as on long highway road trips or in stop-and-go traffic.
Lane keeping systems each can perform slightly differently, depending on the car company and model. For instance, some lane keeping systems only steer as the car leaves the lane, and others work to center the car within lane lines. But with all of them, the driver is still expected to be responsible for the primary task of driving the car. That’s why it’s important that the driver pays attention and that these systems—which are sometimes incorrectly referred to as “semi-autonomous”—are designed to make sure the driver stays engaged.
In Consumer Reports’ first-ever ranking of these systems , conducted in 2018, we evaluated systems from Cadillac, Nissan/Infiniti, Tesla, and Volvo. Over the last two years these advanced technologies have become more mainstream, and CR’s testing this year now includes 17 systems, including the original four.
MORE ON CAR SAFETY
(See below for CR's 2020 ranking of active driving assistance systems .)
Monitoring whether the driver is paying attention is a big part of the reason that Super Cruise is still tops in our ranking. The system uses a small camera facing the driver’s eyes to assess whether they are watching the road ahead. If the system determines that a driver isn’t paying attention, it delivers multiple warnings—such as bright red lights on the upper rim of the steering wheel—to grab the driver’s attention. If the driver still does not react, the system will start to slow the car down on its own, eventually bringing it to a stop. It also will call for help.
CR’s evaluations of active driving assistance systems take into account the work of the National Transportation Safety Board, the federal agency known for investigating plane crashes and other high-profile transportation safety incidents.
In studying deadly highway crashes involving the use of these systems, NTSB investigators have highlighted the risk of “automation complacency”—when people rely too much on an automated system and tune out from the driving task—as well as the foreseeable misuse of the systems in locations or conditions where they haven’t been designed to be used safely. The NTSB has issued recommendations urging the nation’s primary road-safety regulator, the National Highway Traffic Safety Administration (NHTSA), to help develop and then enforce performance standards for safety technology that would help keep drivers engaged while using active driving assistance systems. NHTSA has not yet acted on the recommendations.
“The evidence is clear: If a car makes it easier for people to take their attention off the road, they’re going to do so—with potentially deadly consequences,” says William Wallace, manager of safety policy for Consumer Reports. “It’s critical for active driving assistance systems to come with safety features that actually verify drivers are paying attention and are ready to take action at all times. Otherwise, these systems’ safety risks could end up outweighing their benefits.”
How We Rated the Systems
CR's Auto Test Center, fall 2020.
We put 17 of the newest active driving assistance systems through their paces around our 327-acre Auto Test Center track, as well as on nearby public roads, between June and September 2020. Each system was rated for its performance in 36 separate tests, such as steering the car, controlling the speed, and keeping the driver safe and engaged.
The specific vehicles we tested generally reflect the performance of other models within each automaker’s lineup, but there can be differences among models, model years, and packages that could affect some parameters of how the system operates. So make sure you look out for those potential differences when consulting our rankings as you shop for a vehicle.
Also, some automakers can change their systems software on current and future vehicles with over-the-air updates. Electric carmaker Tesla, for example, does this frequently, which means that certain aspects of its cars change often.
CR’s testers looked at the way each of the 17 systems performed in five specific categories: capability and performance , keeping the driver engaged , ease of use, clear when safe to use , and unresponsive driver .
Capability and Performance
Lane keeping assistance (LKA) provides steering support to assist the driver in preventing the vehicle from departing the lane.
Unlike advanced safety systems, such as automatic emergency braking (AEB), that step in when quick action is needed to help prevent a collision, active driving assistance systems provide features intended to make driving easier—for instance when you’re on a long, boring highway drive or when you get stuck in a barely moving traffic jam. For this category, we judged how well each system kept the vehicle in the center of the lane, as well as how smoothly and intuitively the ACC system could adjust its speed behind other cars.
When it comes to lane keeping assist, Tesla did the best in our tests. But systems from Audi , Cadillac , and Lincoln performed almost as well. A good system will assist the driver by maintaining placement in the center of the lane and keeping the vehicle well within the lane boundaries.
Systems that didn’t perform well, such as those from Buick and Mazda , attempt to assist the driver only as a lane departure occurs, and they aren’t capable of consistently keeping the vehicle between the lane lines, we found.
In response to requests for comment, GM said the system on its Buick Encore GX offers an “impressive amount” of standard active safety features that have been proved to reduce crashes. Mazda responded that its system was not designed or intended to center the vehicle in a lane and that the automaker doesn’t believe its vehicles are equipped with technology that meets the criteria CR is using in its evaluation.
‘Our experience, and the results from CR member surveys, indicate that drivers expect the systems to hold the vehicle in the center of the lane—and if it doesn't do so, they will likely simply stop using the system.’
Head of Connected and Automated Vehicle Testing for Consumer Reports
Volkswagen told us that the Passat we tested was the company’s oldest platform and that VW is beginning to launch newer systems that will do a better job of holding the car more consistently in the center of the lane. We drove the system on the Atlas Cross Sport and it performed similarly.
Systems that scored the best at controlling the car’s speed were those from Audi, Mercedes-Benz , and Porsche , which have options in the menu for drivers to select how quickly the ACC speeds up and slows down. These top-performing systems offer an ample range of following distance and do a good job mimicking natural driving behaviors.
Capabilities and Performance
Test-Drive Before You Buy
When shopping for a new car, be sure to have the salesperson walk you through the details of how these advanced technologies work and how to adjust any specific settings.
As these systems become available on more new cars, it’s important that consumers understand the systems’ limitations, meaning no matter what the automakers might imply in their marketing, none of the systems we tested here are capable of doing the driving for you.
“Automakers also need to realize that the more capable they develop a system in terms of driver assistance, the greater the chances are that the driver might tune out and try to leave the driving to the car,” says Funkhouser. “That’s why driver monitoring is so critical, and should be an essential tool of any good active driving assistance system going forward.”
CR's 2020 Ranking of Active Driving Assistance Systems