Current ACC Too “Dangerous” for Road, Say Insurers

A study has found current adaptive cruise control (ACC) technology is unsafe for consumers.

The report by the Insurance Institute for Highway Safety (IIHS) tested several premium car manufacturers’ products concluding some were “irksome” while others were downright “dangerous”. Its study examined the 2017 BMW 5-series’ Driving Assistant Plus system, the 2017 Mercedes-Benz E-Class’ Drive Pilot, the 2018 Tesla Model 3 and 2016 Model S’ Autopilot versions 8.1 and 7.1 respectively plus the 2018 Volvo S90’s Pilot Assist.

While all of those automatic emergency braking systems are rated ‘superior’ by IIHS, only the two Tesla models passed a test that involved driving towards a stationary vehicle target with ACC off and autobrake turned on. The same test was repeated with ACC switched on and then the 5-series, E-Class, Model 3 and Model S braked earlier than with emergency braking, avoiding the target. However, the owner’s manuals for all these vehicles warn ACC may not brake when it encounters stationary vehicles entering its sensor range.

Worst of all, the test engineers noted instances of each vehicle except the Model 3 failing to respond to stopped vehicles. IIHS senior research engineer Jessica Jermakian says when she was testing the Mercedes-Benz’ ACC, it briefly detected a stopped pick-up truck but then lost sight of it and sped ahead until she braked. She says: “At IIHS we are coached to intervene without warning but other drivers might not be as vigilant. ACC systems require drivers to pay attention to what the vehicle is doing at all times and be ready to brake manually.”

The IIHS also found the Tesla Model 3 braked unnecessarily. Over 180 miles, the car unexpectedly slowed down 12 times, seven of which were for tree shadows on the road. The others were for oncoming vehicles in other lanes or vehicles crossing the road far ahead. Jermakian warns: “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.” Overall, the tests suggest current ACC systems aren’t ready to handle speed control in all traffic situations.

The organisation then tested the systems’ active lane-keeping capabilities. Only the Tesla Model 3 stayed in lane on all of its trials. The Model S performed similarly but over-corrected on one curve, causing it to cross the line on the inside of the curve in one trial. None of the other systems tested provided enough steering input on their own to consistently stay in lane.

The Mercedes-Benz stayed in lane 9 out of 17 times and strayed to the lane marker in five trials. The system disengaged itself in one trial and crossed the line in two. The BMW stayed in lane just 3 out of 16 times, and was more likely to disengage than steer outside the lane. The Volvo stayed in the lane 9 out of 17 times and crossed the lane line eight times.

When testers intervened to avoid potential trouble, the active lane-keeping systems of the BMW, Volvo and Tesla Model S all disengaged and steering assistance only resumed after drivers re-engaged Autopilot. Another issue they noted was a tendency in some of the cars to follow a lead vehicle into the exit lane in slow-moving traffic.

Chief research officer David Zuby said it shows “none of these vehicles is capable of driving safely on its own. 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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