Automation is the best way to improve road safety, but the technology also presents bigger challenges than most realize, Christopher Hart, chairman of the National Transportation Safety Board said Thursday.

The transition will include some deadly accidents, Hart said during an appearance at the National Press Club. But he expects the march to continue – and thinks it should, since done right it will be much better than the status quo.

“There will be fatal crashes, that’s for sure,” Hart said. But “this train has left the station.”

Rolling back opportunities for human error can sharply reduce America’s more than 32,000 yearly road deaths, Hart said, noting that that figure saw a troubling uptick in 2015.

One tool to help the transition: event recorders similar to the “black boxes” used in airplanes, he said.

“We would encourage the use of robust on-board event recorders to help the process,” Hart said, noting that strict privacy protections can and must be put in place. “The more the industry knows from the event recorders about what went right and what went wrong, the more the industry will be able to fashion remedies that effectively address the problems.”

Hart said earlier, deadly automation failures on Washington Metrorail trains and in airline cockpits demonstrate the potential perils, and offer lessons as driverless cars multiply on neighborhood streets and highways.

“The theory of removing human error by removing the human assumes that the automation is working as designed,” Hart said. But when that technology fails, “will it fail in a way that is safe? Will the operator be aware of the failure in a timely manner?”

Success will take cooperation among public and private sectors, as was done in cutting deadly airline accidents, he said.

Perhaps the biggest challenge will be in the transitional world where drivers are still expected to be aware of what their “driverless” car is doing – and where the bulk of cars sharing the road are still driven by humans.

“I would suggest that as difficult as the transition to more automation has been in the structured and regulated environments we have investigated, it may be even more challenging in a public arena, in which drivers are usually not highly trained and may be fatigued, impaired, distracted, or not medically fit,” Hart said.

Underscoring the dangers, officials from the National Highway Traffic Safety Administration said after Hart’s speech that they are investigating that deadly crash of a Tesla Model S, which had its “Autopilot” system activated.

The driver was killed May 7 in Williston, Florida, when the car ran into a tractor-trailer that was turning left in front of him.

“Neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied,” Tesla said in a statement.

Federal investigators “will examine the design and performance of the automated driving systems in use at the time of the crash,” the NHTSA said, adding the launch of such an investigation does not indicate “either a presence or absence of a defect” in the car.

Tesla extended its “deepest sympathies.” It said it was the “first known fatality in just over 130 million miles where Autopilot was activated…. Autopilot is getting better all the time, but it is not perfect and still requires the driver to remain alert.”

Humans can be the weak spot or the nimble savior in a crisis involving automation, Hart said. Or they can be dangerously out of the loop, he said, citing earlier investigations by his agency.

With the 2009 Washington Metro crash near Fort Totten, which left 9 dead, automation failed without a train operator knowing, Hart said. In that case, a Red Line train “temporarily became electronically invisible,” he said. And a train following behind didn’t know what had happened. Given the “electronically unoccupied track ahead, the automation in the train behind began accelerating to the maximum speed for the area,” Hart said.

By the time the trailing operator rounded a curve and saw the stopped train, it was too late for her to stop in time.

That same year, speed-monitoring equipment iced over on Air France Flight 447 from Rio de Janeiro to Paris, shutting down the automatic pilot, automatic throttle and automatic protections to prevent “an aerodynamic stall, in which the wings no longer produce lift,” Hart said.

“The pilots responded inappropriately to the loss of these systems, and the result was a crash that was fatal to all 228 on board,” Hart said. The pilots hadn’t experienced such a problem before, he said. Making things worse still, he said, “use of the automatic pilot is mandatory at cruise altitudes, so the pilots had not flown manually at that altitude before, even in training in the simulator.” And planes behave differently at those higher altitudes, he said.

But well-trained humans can also save the day by being “the most adaptive part of the system,” Hart said. He cited the stunning Hudson River landing by Captain Chesley Sullenberger III after his U.S. Airways plane lost engine power following a bird strike and “suddenly became a glider.” He saved the 155 passengers and crew, and “Sully,” staring Tom Hanks and directed by Clint Eastwood, is set to open this summer.

The U.S. Department of Transportation is set to release guidance on automated cars and model state policies in July. Hart said the safety board can help promote cooperation among car makers and others to help smooth what promises to be an exciting yet “unnerving” transition.

He said automation, particularly collision avoidance technology, is the best way to reduce crashes. Systems that warn of dangers and take control to prevent accidents are “the foundation stones for moving to driverless cars,” he said.

Still, many people are “wildly underestimating” the complexity of the work to come, he said.