WASHINGTON (AP) — The nation's road-safety regulator is under fire again for what critics call lax oversight of tests involving autonomous vehicles.

The nation's top transportation safety investigator said Tuesday that the National Highway Traffic Safety Administration doesn't give enough direction to companies developing more automated cars.

And a member of the Senate Commerce Committee quizzed NHTSA's acting administrator on why the agency hasn't confronted Tesla about widely shared hacks that let drivers take their hands off the wheel.

NHTSA's acting administrator, James Owens, says the agency is assessing autonomous vehicle technology and researching how people interact with it.

The hearing comes a day after the National Transportation Safety Board accused NHTSA of failing to adequately regulate the testing of autonomous vehicles. One board member said NHTSA puts technology advancement above saving lives.