PHILADELPHIA — A woman was drunk and driving a partially automated driving system when she caused a highway crash in Philadelphia in March that killed two people, authorities said after announcing manslaughter charges against the driver.

State and federal investigators say the woman’s Ford Mustang Mach-E SUV struck the stopped vehicle of a man who had stopped on the left shoulder of I-95 to help a driver whose car had crashed in front of him. The March collision, which occurred around 3 a.m., killed both men.

It was at least the second crash this year in which a Mach-E struck a stopped vehicle at night that the National Transportation Safety Board has investigated. In a February crash along Interstate 10 in San Antonio, Texas, investigators believe a Mach-E struck a Honda CR-V that was in the center lane without its lights on. The driver of the CR-V was killed.

In a statement Tuesday, the Pennsylvania State Police said drivers using advanced technologies should be prepared to regain control at all times.

“No partially automated vehicle technology should ever be left alone to perform the driving tasks necessary to safely navigate the Commonwealth’s roadways,” the agency said.

Ford’s Blue Cruise system lets drivers take their hands off the wheel while the system handles steering, braking and acceleration on highways. The company says the system is not fully autonomous and that it monitors drivers to ensure they’re paying attention to the road.

Philadelphia investigators believe Mustang driver Dimple Patel was traveling at about 71 mph (114 km/h), with both Blue Cruise and Adaptive Cruise Control engaged, when the crash occurred. A fourth vehicle was also struck.

Patel, 23, a pre-med student from Philadelphia, faces multiple charges, including vehicular manslaughter while driving under the influence and involuntary manslaughter. She turned herself in to police Tuesday on the charges that were filed last week, state police said.

Defense attorney Zak Goldstein said he had not seen the criminal complaint or reports on the crash and called the deaths a tragedy. However, he noted that Pennsylvania law on DUI-related homicides generally requires that “the DUI caused the homicide.”

“If it is in fact a malfunction of a self-driving car or a driving system, there may not be a DUI manslaughter case even if the driver is intoxicated,” he said, adding that he has not seen any case law on this in Pennsylvania.

Ford said it was working with state police, the NTSB and the National Highway Traffic Safety Administration in investigating the crash, which killed Aktilek Baktybekov, who was broken down, and Tolobek Esenbekov, who is believed to have stopped on the side of the road to help him.

When NHTSA opened an investigation into the Philadelphia and San Antonio crashes involving Blue Cruise, the agency noted that both crashes occurred on freeways under nighttime light conditions and that Blue Cruise had been in use shortly before the crashes.

The agency says it is investigating how Blue Cruise performs driving tasks and how its camera-based driver monitoring system works.

Both the NHTSA and NTSB have investigated several previous accidents involving partially automated driving systems.

In April, NHTSA began investigating whether Tesla’s solution to a December recall of more than 2 million vehicles equipped with the company’s partially automated Autopilot system had fixed the problem. The recall was issued because the driver monitoring system was inadequate and posed a safety risk.

NHTSA reported that between January 2018 and August 2023, there were 956 crashes involving Autopilot and Tesla’s Full Self Driving systems, resulting in 29 deaths.

____

AP Auto Writer Tom Krisher in Detroit contributed to this report.