Phantom braking dents tech confidence

Tesla, Honda and many other automakers that offer automated braking systems have been stung by a phenomenon known as phantom braking, which may cause vehicles to suddenly slow — or stop — in response to what the system mistakenly perceives as a obstacle.

Phantom braking, also known as unintended braking, is caused by erroneous sensor perception in systems that are now standard equipment on most new light vehicles sold in the U.S.

Among the latest developments:

• In February, it was reported Tesla faced a probe in the U.S. after authorities received more than 354 complaints for unexpected brake activation in the 2021-22 Model 3 and Model Y.
• A California owner of a Tesla Model 3 sued the electric vehicle maker in a proposed class action related to phantom braking, calling it a "frightening and dangerous nightmare," according to the lawsuit.

• Honda is under an NHTSA investigation for a phantom-braking issue affecting more than 1.7 million vehicles. NHTSA has received more than 270 complaints that allege braking incidents "occurring with nothing obstructing the vehicle's path of travel," with six people alleging they were involved in a collision resulting in minor injuries.

While the actions against Tesla and Honda put their technology under scrutiny, they are not alone and the false-positive problem is not new.

A 2017 Mercedes E-Class owner wrote NHTSA in August 2021 that "The vehicle independently came to an abrupt stop." That same month, the agency got this from the owner of a Volvo S60: "The automatic emergency braking engaged while we were traveling between 60-70 mph. … There was no apparent reason for the braking because there was no vehicle or other obstacle to trigger the braking."

NHTSA investigated a rash of false-positive incidents involving the Nissan Rogue in 2019. Nissan told the agency it received 750 vehicle complaints "relating to false-positive activation" of the automatic emergency braking system. Of these complaints, 12 said a collision resulted from the system's activation, with four people alleging they sustained injuries in those crashes.

"I have seen how these systems are being developed, and you can never make 100 percent sure these systems are going to deliver full performance across a wide variety of situations," said Adriano Palao, technical manager of ADAS and automated driving for car testing agency Euro NCAP.

Eliminating phantom braking is especially difficult in Europe "where we have a wide variety of infrastructure across countries," Palao said.

Rather than relying on a single input, one solution is to use multiple modes of sensing combinations, drawing from a mix of radar, lidar and camera inputs that are digested by artificial intelligence.

Problems start when automakers skimp on the number and performance of sensors or system training to address a particular situation, according to Gartner analyst Pedro Pacheco.

"This is, obviously, due to cost considerations," he said.

Phantom braking is "a huge problem" because it undermines confidence in what is designed to be a potentially life-saving system, Palao said. "Then the safety benefit is just gone because the driver will no longer trust the systems, and they will start switching them off," he said.

Overall, such systems are making signifcant safety contributions. Cars equip-ped with forward collision warnings and automatic braking cut rear-end crashes in half, while warnings alone reduced crashes by 27 percent, according to a study conducted by the Insurance Institute for Highway Safety. A separate IIHS study issued earlier this year found that braking systems that recognized pedestrians also reduced pedestrian-related collisions by 27 percent.

To continue improvement, Euro NCAP will devise ways to address the robustness of the technology to determine which brands offer the best solutions to a wide range of challenging real world scenarios, Palao says.

Motoring organization AAA said in September that its U.S. testing demonstrated automakers should update their systems, which were designed to limit crashes at slow speeds. AAA found at 30 mph, automatic braking prevented a rear-end collision in 17 of 20 test runs, an 85 percent success rate.

Braking reduced the impact speed by 86 percent. But at 40 mph, the system only prevented a rear-end crash in six of 20 test runs, a 30 percent success rate. In the crashes, the impact speed was reduced by 62 percent.

The systems didn't work in other types of crash tests, such as T-bone collisions and left turns in front of oncoming vehicles.

AAA tested 2022 models including the Chevrolet Equinox LT, Ford Explorer XLT, Honda CR-V Touring and Toyota RAV4 LE.

"Automatic emergency braking does well at tackling the limited task it was designed to do," Greg Brannon, director of AAA's automotive engineering and industry relations, said in a statement. "Unfortunately, that task was drawn up years ago, and regulator's slow-speed crash standards haven't evolved."

Jerry Hirsch contributed to this report.