Tesla Motors said Sunday that the company is changing its Autosteer semi-autonomous feature so that drivers of the Model S sedan and Model X SUV who ignore repeated warnings to put their hands on the wheel will have to restart the car before using the feature again. Tesla vehicles also will rely more on their integrated radar systems to detect objects after the software update.

Tesla CEO Elon Musk told reporters on a conference call that drivers who ignore three audible warnings in an hour will have to pull over and start the car again to use the Autosteer feature, which allows the car to steer itself and is part of its Autopilot system.

The changes are part of an overall upgrade to Tesla's Autopilot software, which the electric automaker expects to roll out in one to two weeks. The company updates owners' cars wirelessly. Consumer Reports owns a Model S and Model X, and will evaluate the update as soon as it’s available.

Tesla also is adding a pulsing visual cue to the instrument panel lights when drivers are warned to put their hands back on the wheel. But it is not changing the system to require drivers to always keep their hands on the wheel, something Consumer Reports has called for.

"While they have added additional checks to confirm driver engagement, we are still concerned with the length of time that drivers can take their hands off the wheel or not have their eyes on the road,” said Jake Fisher, Consumer Reports director of auto testing.

Musk said drivers can indefinitely keep their hands off the wheel under 8 miles an hour, such as in stop-and-go traffic conditions. Below 45 miles an hour, drivers can keep their hands off the wheel for about 5 minutes, he said. Above 45 miles an hour, the limit is about 1 minute unless the Tesla has a car to follow, and then it's about 3 minutes.

He added that the people who currently misuse Autosteer are what he termed expert users. Tesla knows how owners drive because each car transmits information back to the company as part of an effort to use data from thousands of cars to make each smarter. Some "experts" will get as many as 10 warnings an hour, and simply tug the steering wheel each time, Musk said.

"We really want to avoid that situation," he said.

The shift to make radar a more important part of how a Tesla sees its surroundings will allow the car to make out objects through rain, fog, or dust, Musk said. The radar, he said, also will work to spot objects beyond the car directly in front of a Tesla.

Until now, Teslas have relied primarily on a camera-based system to detect obstacles. In some cases in the past, a Tesla might not react to something the radar saw if the camera didn’t see it. The new system will use the radar and the cameras side by side, Musk said. And the radar will now become the primary sensor without requiring verification from the camera, Musk wrote on Tesla’s blog.

“Making the camera and radar systems work side by side is an important step in establishing redundancies where each system can back the other up in conditions where they don’t have full capabilities,” said Consumer Reports’ Fisher. “This is a key part of safety in semi-autonomous cars where none of the systems have yet proven to be fail-safe.”

In May, a Tesla Model S in Autopilot mode didn't spot a semi-tractor trailer pulling across a Florida highway in front of it. The resulting accident killed the driver of the Tesla, Joshua Brown. Tesla said in June that "neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied."

Musk was asked whether the upgrade would've saved Brown's life. "We believe it would have," he said, adding that the radar system likely would see a large metal object across a road.

The company also believes it can reduce false positives with radar by using information from other cars. For instance, if one object on a road causes repeated false positives, Tesla would record the object and its location so other cars traveling the same road in future wouldn't react to the object.

But Musk cautioned that no system is completely safe.

"Perfect safety is really an impossible goal," he said. "It's really about improving the probability of safety."

Consumer Reports believes that a key part of improving this probability of safety is ensuring consumers have the appropriate expectation for how the system will perform and continues to call on Tesla to rename Autopilot, so people do not have a false sense of security.