The phenomenon, known as “phantom braking,” has been a persistent issue for Tesla vehicles.

The automaker was forced to recall a version of its Full Self-Driving software in October over false positives to its automatic emergency-braking system that it said were triggered by the software update. Complaints soared after the recall and remain elevated, signaling continued owner concern.

Owner reports of phantom braking to NHTSA rose to 107 complaints in the past three months, compared with only 34 in the preceding 22 months.

In addition to the safety recall in late October, the timing of the complaints coincides with a period in which Tesla has stopped using radar sensors in its vehicles to supplement the suite of cameras that perceive their surroundings. Tesla announced last year that it would stop equipping Tesla Model Y and Model 3 vehicles built in North America with radar beginning in May 2021. Tesla’s new approach is known as “Tesla Vision.”

Tesla vehicles are equipped with eight surround-view cameras that the automaker says “provide 360 degrees of visibility around the car at up to 250 meters of range.” It also leverages 12 ultrasonic sensors to detect objects around the vehicle. Tesla eventually wants to transition its fleet to Tesla Vision, and some owners have been left wondering whether their cars’ radar sensors will be disabled.

Drivers and safety experts said they believe the systems began acting erratically after the changes.

Several of the owners who filed complaints with regulators said their cars seemed overly sensitive to trucks in the opposite lane. One owner described how around noon on a straight road, the car lurched from 50 mph to a near-stop seemingly in response to a large truck.

“[It] was scary to almost stop in the middle of my lane,” the owner wrote.

“Phantom braking is what happens when the developers do not set the decision threshold properly for deciding when something is there versus a false alarm,” said Phil Koopman, a Carnegie Mellon University professor who focuses on autonomous vehicle safety. “What other companies do is they use multiple different sensors and they cross-check between them — not only multiple cameras, but multiple types of sensors,” such as radar and lidar, a type of sophisticated sensor that uses laser lights to paint a dot matrix mapping the environment.

“With only one sensor type, it’s harder to be sure because you do not have the cross-check from a different type of sensor,” he said.

The NHTSA complaints are not individually verified by the agency. Owners submit their description of the issue, their vehicle identification number and other identifying information when they report their problems to the agency. NHTSA spokeswoman Lucia Sanchez said the agency is engaging in a dialogue with Tesla over the phantom braking reports.

“NHTSA is aware of complaints received about forward collision avoidance and is reviewing them through our risk-based evaluation process,” she said. “This process includes discussions with the manufacturer, as well as reviewing additional data sources, including Early Warning Reporting data. If the data show that a risk may exist, NHTSA will act immediately.”

Tesla, which disbanded its public relations department in 2020, did not respond to a request for comment. The automaker has contended in the past that its driver-assistance feature suite, Autopilot, is safer than typical driving when crash data is compared. Autopilot is a system primarily intended for highway use, so the data cannot be directly compared with vehicle crashes overall. Tesla’s chief executive, Elon Musk, has called Autopilot “unequivocally safer.”

But the company faces mounting scrutiny from regulators, including recalls and safety investigations that called into question the responsibility and performance of its driver-assistance approach.

Tesla initiated a safety recall of its Full Self-Driving driver-assistance software late last month because of a feature than enabled it to conduct “rolling stops,” proceeding through intersections with stop signs without fully halting. Tesla had met with NHTSA officials twice in January to discuss the issue, part of growing safety concerns about the cars’ automation-targeted software. NHTSA opened a safety investigation in August over about a dozen reports of crashes with parked emergency vehicles while Autopilot was activated.

The Post analysis covered more than a year of data for Tesla vehicles from the four most recent model years.

Owners of the 2022 Tesla Model 3 complained 20 times about the issue known as phantom braking, where the car suddenly slows or stops with no external cause, out of 22 total complaints involving the model.

The events are typically triggered by false positives of the forward collision warning and automatic emergency-braking systems. Owners often cited their use of Tesla’s Autopilot driver-assistance system or traffic-aware cruise control in their complaints. They also commonly referred to issues on two-lane highways, where the system was triggered by an oncoming truck in the opposite lane.

The bulk of the complaints recently about Tesla cars have been related to the phantom braking issue — 107, or 57 percent, out of 189 complaints since November about the 2020 through 2022 Tesla Model Y and Model 3, along with the 2019 Tesla Model 3.

Some drivers recalled instances of phantom braking even when they were not using Autopilot. Other owners said in complaints to NHTSA that they were shaken by the incidents and feared being rear-ended.

“These events are hair raising for me and passengers, let alone for a driver behind me,” one owner wrote in a report to the agency. “If he/she does not pay attention at that very moment, the result could even be disastrous. I would never have expected such a serious safety issue with a Tesla.”

Owners also said they experienced the phenomenon one or multiple times while on extended trips. Some said their road trip experiences were marred by the brakes suddenly triggering or the frequency jolts made by their cars.

“My wife has requested that I don’t use cruise control or autopilot while she’s in the car, as we experienced an unwarranted, aggressive automatic braking episode which caused great pressure against her pregnant belly on a previous road trip,” one owner said in a report.

Owners’ comments reflected apparent exasperation with the recurrence of the problem and a seeming inability to get it fixed.

“[These] things are happening with NOTHING present in front of my vehicle, and sometimes with nothing around me at all,” one wrote.

Luis Fernandez, who drives a 2022 Tesla Model Y, said he was at Taylor Street and Pine Street in San Francisco recently when his car spotted a plastic bag several feet in front of him. The bag didn’t pose a hazard and was soon out of his view, said Fernandez, who uses the vehicle to drive for Uber.

But his car jolted him from 25 mph to 15 mph before he could intervene.

“Suddenly the car kind of locked, but it immediately released because the plastic bag moved away. . . . The car just completely took precaution,” he said. “Automatically, it braked.”

A 2021 Tesla Model Y owner, Ben Morris, confirmed that he was one of the people who filed a complaint with NHTSA. He said this was his third Tesla, and the issues presented themselves more than ever before on his other models.

“We primarily drove the car on two-lane highways, which is where the issues would show themselves consistently,” he said in an email. “Although my 2017 Model X has phantom braked before, it is very rare, the vision-based system released May 2021 is night and day. We were seeing this behavior every day.”

He recalled an instance when his wife was driving at highway speeds of 55 to 60 mph and “it slammed on the brakes hard, sending our children’s booster seats slamming into the front seats.”

Thankfully, he said, the children weren’t in the car.

Chris Alcantara contributed to this report.