ADAPTIVE CRUISE CONTROL

Adaptive cruise control, active lane-keeping, and other automated features can all be useful in preventing crashes. But the Insurance Institute for Highway Safety is reminding drivers that they should continue to be vigilant behind the wheel, since these systems aren't yet reliable enough to take over driving tasks.

IIHS recently completed several tests on both public roads and tracks in its efforts to develop a ratings system for advanced driver assistance systems. The systems showed variable reliability, exhibiting behaviors ranging from overly cautious braking to veering toward the shoulder when lane markings could not be detected.

Advanced driver assistance programs are part of automakers' efforts to develop fully self-driving vehicles, which are defined as Level 5 on a scale developed by SAE International. IIHS looked specifically at vehicles with a combination of adaptive cruise control and active lane-keeping systems, which are considered to be at Level 2. While the systems can assist with driving tasks, human drivers are still in charge of safely operating the vehicle.

The testing comes in the midst of greater scrutiny of advanced driver assistance programs, particularly the Autopilot system developed by Tesla. Earlier this year, two American consumer rights groups accused the system's name of being "deceptive and misleading," causing several drivers to rely too heavily on the system.

Tesla has stressed that drivers need to remain focused while using the system, a small number of crashes and incidents have occurred while Autopilot was activated. The National Transportation Safety Board said a fatal 2016 crash involving a Tesla was due in part to the driver's "inattention due to overreliance on vehicle automation," and a British man had his license suspended earlier this year after he was caught riding in the passenger seat while the Autopilot system was activated.

"Designers are struggling with trade-offs inherent in automated assistance," said David Zuby, chief research officer at IIHS. "If they limit functionality to keep drivers engaged, they risk a backlash that the systems are too rudimentary. If the systems seem too capable, then drivers may not give them the attention required to use them safely."

"The new tests are an outgrowth of our research on Level 2 autonomy," said Jessica Jermakian, senior research engineer at IIHS. "We zeroed in on situations our staff have identified as areas of concern during test drives with Level 2 systems, then used that feedback to develop road and track scenarios to compare vehicles."

Researchers used a 2016 Tesla Model S and 2018 Tesla Model 3, each equipped with Autopilot, as well as a 2017 BMW 5-series with Driving Assistant Plus, a 2017 Mercedes-Benz E-Class with Drive Pilot, and a 2018 Volvo S90 with Pilot Assist for the testing.

Adaptive cruise control systems adjust a vehicle's speed to maintain a following distance from a lead vehicle. The IIHS tests evaluated how the different systems reacted in a variety of common scenarios.

Each vehicle decelerated smoothly when the lead vehicle slowed to a stop before accelerating. Most vehicles also had a smooth deceleration when the adaptive cruise control system was set to differing following distances, although the S90 braked more forcefully. This vehicle also decelerated more aggressively in a test where a lead vehicle changed lanes to reveal a stationary inflatable vehicle target ahead, with 4.3 seconds to react before a collision.

Researchers noted how track tests can differ from real world performance, citing the reaction of adaptive cruise control to stopped vehicles as an example. Each of the test vehicles' owners manuals warn that the system may