Could software updates replace recalls in cars of the future?

About 34 million U.S. drivers have gotten bad news in the mail: Their car has been recalled because the air bags might explode. Only a small fraction of them have responded to that or to a massive federal campaign begging them to head down to the dealer for repairs.

In the decades to come, however, many auto recalls may take no more than the push of a computer button.

Yes, defective air bags and faulty brakes still will require a trip to the dealership. But the brains of a vehicle - what gradually may replace the driver - is software that operates the car's decision-making computer systems. And software, as anyone who owns an iPhone or laptop knows, can be easily updated over-the-air.

"They will be able to essentially remedy a recall without actually ever having to go into a dealership," said a senior official of the National Highway Traffic Safety Administration. "As long as the [automaker] could demonstrate that they have remedied the recall, that is ultimately what we're looking for from a safety standpoint."

NHTSA guidelines released this week ask automakers to comply with 15 requests before they put their driverless cars on the road. The agency asked for notification any time software updates "materially change" the manner in which the vehicles function.

One of the remote software updates happened this week.

Chinese hackers were able to take over some systems on Tesla's Model S vehicle, a car equipped with what is called a "driver assist" autopilot that can take control of the car under limited circumstances. The "white hat" hack by Keen Security Lab was intended to alert Tesla to its vulnerability by demonstrating the hackers' ability to perform tasks like unlocking the car's doors, opening the sunroof and moving the seats remotely.

Tesla said it responded to the hack within 10 days, sending an over-the-air security fix to all its susceptible vehicles this week. Tesla said it has done similar updating in the past, without requiring a visit to the auto shop by its owners.

On Wednesday night, Tesla also began sending out a software update it said probably would have prevented the crash that killed a driver using the company's autopilot system in May.

The updated software will allow the cars to brake automatically when existing onboard radar technology sees a hazard ahead. Previously, the brakes would automatically kick in based largely on what the cars' cameras detected.

On a Florida highway earlier this year, the existing system failed spectacularly, with tragic results, when a truck turned in front of a speeding Tesla driver. At the time, the company said "neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied."

The driver died when his car passed under the truck's trailer.

Google, a pioneering developer of autonomous vehicles that plans to retain ownership of its fleet once production starts, said it plans to provide over-the-air software updates. A Google spokesman said the company's 60 test vehicles are updated each week. He declined to say what mode of transmission - over the air or insertion of a flash drive in each car's computer - was used for those updates.

The prospect that updates and recalls can be conducted over-the-air excites NHTSA officials, who have been frustrated when car owners are slow to react to the recall of vehicles for serious safety concerns.

In the recall of Takata air bags installed in cars built by dozens of automakers, fewer than 10.7 million air bags have been replaced. Since some vehicles have front and side air bags, that number is just a fraction of the estimated 34 million vehicles that have been recalled.

Over-the-air software updates like Tesla's could remedy significant safety recalls when fully autonomous cars go into production.

"One of the great strengths of this is that you can get 100 percent recall," a second NHTSA official said. "One hundred percent recall is always our goal. It's a very, very hard goal. Over the years with software it can come closer to reality."

Several NHTSA officials briefed reporters on the new guidelines earlier this week on the condition of anonymity.

NHTSA guidance also encouraged automakers to collaborate in an unprecedented fashion, sharing safety issues they discovered while developing their vehicles and after their cars take to the streets.

"What we are looking at now is being able to provide a huge amount more information, much earlier in the process, and engage in a dialogue with the manufacturers," the second NHTSA official said. "Our goal is to work with the manufacturers much earlier so that we're attacking safety problems and addressing safety problems much earlier in the process."