TSLA Tesla Inc

Tesla Motors Inc. is changing the way its Autopilot system works following the fatal crash in May of a car that was driving under semi-autonomous control.

The revision, which Tesla Chief Executive Elon Musk outlined Sunday, will depend more on radar signals to help guide Tesla vehicles along roadways, and adds safeguards to keep drivers engaged at high speed.

The software updates will be rolled out within the next two weeks and delivered to vehicles over the air, he said. They will affect Tesla vehicles built since October 2014, before which the hardware used by Autopilot wasn't included.

Autopilot, which uses cameras, radar and sensors to steer vehicles and adjust their speed, has come under scrutiny since the Florida crash that killed Tesla driver Joshua Brown in May, the first known death of a driver using the system.

The car in the May 7 incident failed to brake automatically because the system didn't distinguish a truck's white trailer from the bright sky, Tesla has said.

The National Highway Traffic Safety Administration is investigating the crash, focusing on the emergency-braking and forward-collision warnings.

The changes announced on Sunday might have prevented the accident, Mr. Musk said.

Mr. Musk told reporters on a conference call that the changes will make the system even safer. "This is not going from bad to good. It's going from good to, I think, great."

"Ultimately, this will probably be a threefold improvement in safety" compared with the current version, Mr. Musk told reporters on a conference call. "This is not going from bad to good. It's going from good to, I think, great."

Autopilot is regarded as a major step toward self-driving cars, though Tesla warns users that the technology doesn't make Tesla vehicles autonomous and that drivers must remain ready to take control.

Despite those warnings, some experts have questioned whether the technology might lead users to rely too much on the vehicle's driving capabilities.

Consumer Reports, for example, wrote that Autopilot was " too much autonomy too soon."

As part of the changes to Autopilot, the system will disengage if drivers ignore three warnings within the span of an hour to keep their hands on the wheel. To reactivate the system, the vehicle would have to be stopped and restarted.

Mr. Musk has vigorously defended the Autopilot technology, saying it improves safety. When activating the system, drivers must acknowledge by clicking on a screen that they are responsible for the vehicle.

Radar, which was added to Tesla vehicles in October 2014, had been a supplement to the onboard camera and image-processing technology, the company said Sunday.

Using radar, which detects objects by sending out pulses of electromagnetic waves to detect objects, to guide vehicles is complicated because the waves interact differently than light waves with objects in the roadway.

"The big problem in using radar to stop the car is avoiding false alarms," Mr. Musk wrote in a blog post on the company's website. "Slamming on the brakes is critical if you are about to hit something large and solid, but not if you are merely about to run over a soda can."

Part of the solution, according to Mr. Musk, is to take advantage of Tesla vehicles' ability to communicate with one another and collaborate on their understanding of road conditions. "The net effect of this…is that the car should almost always hit the brakes correctly even if a UFO were to land on the freeway in zero visibility conditions," Mr. Musk wrote.

Tesla's decision to update its radar software intensifies Mr. Musk's bet that radar is an effective technology to help cars navigate the world. Alphabet Inc.'s Google unit and others racing toward fully self-driving cars are counting on a technology known as lidar, which is similar to radar but uses lasers.

Mr. Musk reiterated on Sunday that he doesn't anticipate using lidar because it doesn't have the same capabilities as radar.

Asked whether the improvements would have prevented the fatal Florida crash, Mr. Musk said he believed so because the radar would have detected the trailer. "It would see a larger metal object across the road," he said.

Some Tesla drivers have admitted that Autopilot's success may have lulled them into a false sense of security. "I look down at my phone a little more than I used to," Jason Hughes, an Autopilot user from Hickory, N.C., told The Wall Street Journal in July. "People are overly confident in it, in my opinion. They think it can do magical things, but it can't go beyond what its sensors tell it."

Mr. Musk appeared to acknowledge this on Sunday, saying that Autopilot accidents are far more likely among expert users then novices. The current system alerts drivers when their hands have been off the wheel too long depending upon driving conditions, and it slows the vehicles if they don't respond. Some users ignored 10 warnings to keep their hands on the wheel in an hour, he said. "They get very comfortable with it and repeatedly ignore the car's warnings," he said. "We really want to avoid that situation.".

As he responds to Tesla safety concerns, Mr. Musk also faces controversy for proposing in June to combine Tesla and SolarCity Corp., where he is chairman, and questions why one of his Space Exploration Technologies Corp. rockets exploded during routine fueling on Sept. 1.

Write to Tim Higgins at Tim.Higgins@dowjones.com

(END) Dow Jones Newswires

September 11, 2016 21:15 ET (01:15 GMT)

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