In addition to Tesla’s efforts, the competition to develop self-driving cars has become fierce among auto industry giants such as General Motors and Ford Motor, as well as technology companies including Google and Apple.

The companies have been accelerating their testing and have backed legislation exempting autonomous vehicles from current motor vehicle laws.

Some safety campaigners and consumer groups have been critical of the move toward voluntary rules covering self-driving technology, including the guidelines introduced by Ms. Chao, saying they reduce federal oversight that was already too limited.

“The voluntary policy announced today is a retreat from the already flawed guidance provided in 2016,” said Jason K. Levine, the executive director of the Center for Auto Safety in Washington. He said the lack of required safety assessments cedes power to automakers “who have frequently proven they cannot be trusted to protect the public interest in their race for profits.”

Automakers and government officials contend that self-driving technology could reduce vehicle accidents and traffic fatalities, which rose by nearly 8 percent in 2015 to more than 35,000 deaths. Tesla reiterated that safety potential Tuesday after the transportation safety board issued its report on the Florida crash.

The accident killed Joshua Brown, 40, of Canton, Ohio. His 2015 Tesla Model S was operating under its Autopilot system on May 7, 2016, on state highway in Williston, Fla., when it crashed into a tractor-trailer that was crossing the road in front of him.

The system’s forward-looking camera failed to recognize the white truck against a bright sky, and neither Mr. Brown nor the Autopilot system activated the brakes. Data from the car showed it had been traveling at 74 miles per hour at the time of the crash and that Mr. Brown had ignored several warnings to keep his hands on the steering wheel. A preliminary N.T.S.B. report found that he had at least seven seconds to notice the truck before impact.