Mainstream vehicles are inching closer to autonomy as driver assistance systems trickle down through many automakers' lineups. These systems are not all equal, however, and the Insurance Institute for Highway Safety is creating a consumer ratings program to test them. The agency's early take on the new tests is that none of the systems should be considered a substitute for a human driver.
In creating the program, IIHS began testing two popular systems — adaptive cruise control and active lane-keeping systems, which assist with steering, speed control and following distance, but the human driver is still in charge and must stay alert to intervene. On SAE International's autonomy scale of zero to Level 5 full autonomy, a vehicle with both systems is rated Level 2.
The agency tested several Level 2 vehicles - the 2017 BMW 5 Series with Driving Assistant Plus, 2017 Mercedes-Benz E-Class with Drive Pilot, 2018 Tesla Model 3 and 2016 Model S with Autopilot (software versions 8.1 and 7.1, respectively), and 2018 Volvo S90 with Pilot Assist — with mixed results related to each system.
How Adept Is Adaptive Cruise Control?
In testing adaptive cruise control — which maintains a set speed and following distance from the vehicle in front and may or may not be able to come to a full stop depending on the vehicle and traffic situation — engineers evaluated the systems on the road and track to see how they handle stopped lead vehicles and vehicles exiting the lane, as well as how the systems accelerated and decelerated.
During a test that involved the vehicles following a lead vehicle going 31 mph, which then changed lanes to reveal a stationary inflatable target in its path, none of the vehicles crashed, and the 5 Series, E-Class and Teslas all braked earlier and gentler than the S90. Results were more mixed when speeds rose.
In several tests, the S90's braking proved to be harsher and more jarring than in the other vehicles. The Model 3 was also dinged for its braking behavior, with engineers noting unnecessary or overly cautious braking. In a 180-mile test, the Model 3 unexpectedly slowed down 12 times; seven of those times were for tree shadows.
While IIHS believes adaptive cruise control systems are a bonus in terms of comfort and safety, the agency concluded that they aren't ready to handle speed control in all traffic situations.
"The braking events we observed didn't create unsafe conditions because the decelerations were mild and short enough that the vehicle didn't slow too much," Jessica Jermakian, IIHS senior research engineer, said in a statement.
"However, unnecessary braking could pose crash risks in heavy traffic, especially if it's more forceful.
"Plus, drivers who feel that their car brakes erratically may choose not to use adaptive cruise control and would miss out on any safety benefit from the system."
In testing active lane-keeping systems, which look at road markings or the vehicle ahead and automatically provide steering input to stay in the lane, engineers zeroed in on two challenging areas for the systems: hills and curves, both of which can obscure road markings. Each vehicle was tested on a road course that included three hills with different slopes. The E-Class and Model 3 stayed in the lane the most, and their systems continuously provided steering support without erratic moves when lane lines weren't visible.
The others struggled. The 5 Series steered toward or across the line frequently, requiring much correction from the driver; the car failed to stay within the lane in every trial. The Model S was able to stay in the lane only five out of the 18 trials and regularly veered into the wrong lane. Engineers also noted its unsettling tendency to swerve left and right until it was able to determine the correct place in the lane. The S90 stayed in the lane nine out of 16 times; its system tended to automatically disengage when it crested hills and then re-engage when it once again detected the lane markings.
Despite the systems' faults, IIHS says their merit is clear: The agency's research shows that preventing lane departure crashes could save nearly 8,000 lives a year. However, IIHS is stopping short at recommending which vehicle or automaker does it best, and further cautions drivers about the danger of overreliance on such systems.
"We're not ready to say yet which company has the safest implementation of Level 2 driver assistance, but it's important to note that none of these vehicles is capable of driving safely on its own," David Zuby, IIHS chief research officer, said in a statement. "A production autonomous vehicle that can go anywhere, anytime isn't available at your local car dealer and won't be for quite some time. We aren't there yet."
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