The Insurance Institute for Highway Safety (IIHS) has been releasing some information about their autonomous driver assist level 2 system tests in some premium sedans and they found that the Tesla Model 3 has the best lane-keeping with Autopilot’s Autosteer, but they had some issues with other aspects of Autopilot and its active safety features of both Model S and Model 3.

They tested the automatic emergency braking of the 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”.

In the test with a stationary vehicle target, they said that only the two Tesla vehicles failed to avoid the target:

“One series involved driving at 31 mph toward a stationary vehicle target with ACC off and autobrake turned on to evaluate autobrake performance. Only the two Teslas hit the stationary target in this test.”

Update: Tesla says that while the cars didn’t completely stop to avoid the target, they still slowed down to mitigate the crash as their automatic emergency braking system is designed.

With Adaptive Cruise Control (ACC) activated, which Tesla calls Traffic Aware Cruise Control (TACC), Tesla vehicles performed much better:

“With ACC active, the 5-series, E-Class, Model 3 and Model S braked earlier and gentler than with emergency braking and still avoided the target. The cars slowed with relatively gradual decelerations of 0.2-0.3 gs, braking in the same manner no matter the distance setting. Braking before impact was earlier for the Teslas than for the 5 series and E-Class.”

As far as lane-keeping, IIHS was impressed with the Model 3’s Autosteer. Not so much with the Model S’, but they hadn’t updated the vehicle’s software for over 2 years.

They said about the Model 3:

“Curves and hills can challenge active lane-keeping systems. The Tesla Model 3 performed well in these on-road tests.”

IIHS compared the Model 3 Autopilot’s Autosteer to Mercedes-Benz’s Drive Pilot:

“The E-Class stayed in its lane in 15 of 18 trials and on the line in one trial, continuously providing steering support without erratic moves when lane lines weren’t visible. The Model 3 also stayed in the lane in all but one trial, when it hugged the line.”

They also liked TACC:

“Out on the road, engineers noted instances in which each vehicle except the Model 3 failed to respond to stopped vehicles ahead.”

But they found it to be over-cautious on a few occasions:

“Unnecessary or overly cautious braking is an issue IIHS noted in the Model 3. In 180 miles, the car unexpectedly slowed down 12 times, seven of which coincided with tree shadows on the road. The others were for oncoming vehicles in another lane or vehicles crossing the road far ahead.”

As usual, keep in mind that Tesla’s Autopilot, like any other level 2 system, requires the driver to always stay attentive and be ready to take control.

Here’s IIHS’ full report:

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