U.S. Transportation Secretary Pete Buttigieg said Tuesday there are concerns about the interaction between Tesla's advanced driver assistance system Autopilot and drivers that is the subject of an ongoing government investigation.

Since August 2021, the National Highway Traffic Safety Administration (NHTSA) has been investigating a series of Tesla crashes involving Autopilot and with parked emergency vehicles and whether Tesla vehicles adequately ensure drivers are paying attention.

"There is a real concern that's not limited to the technology itself but the interaction between the technology and the driver," Buttigieg told reporters when asked about the Tesla Autopilot probe.

Buttigieg said advanced driver assistance systems can benefit drivers. "The question is not are they absolutely free of problems or 1000 percent foolproof," Buttigieg said. "The question is, how can we be sure that they will lead to a better set of safety outcomes ... This technology has a lot of promise. We just have to make sure it unfolds in a responsible fashion."

Tesla did not respond to a request for comment.

In January, Acting NHTSA Administrator Ann Carlson said the agency was "working really fast" on the Tesla Autopilot probe.

In June 2022, NHTSA upgraded to an engineering analysis its defect probe into 830,000 Tesla vehicles with Autopilot and involving crashes with parked emergency vehicles.

NHTSA has said evidence suggested drivers in most crashes under review had complied with Tesla's alert strategy that seeks to compel driver attention, raising questions about its effectiveness.

In 2020, the National Transportation Safety Board criticized Tesla's "ineffective monitoring of driver engagement" after a 2018 fatal Autopilot crash, and said NHTSA had provided "scant oversight."

NHTSA in April opened an probe into whether Autopilot or other advanced driver systems were in use when a Tesla struck a 17-year-old student who exited a school bus in North Carolina.

Since 2016, NHTSA has opened 40 Tesla special crash investigations where driver assistance systems like Autopilot were suspected of being used, with 20 crash deaths reported. The agency has ruled out Tesla Autopilot use in three other special crash investigations.