Google's self-driving car has been hailed as the next giant leap for the auto industry, but the shift could also allow the technology giant to keep an even tighter grip on our lives.

Part of the in-depth ReadWriteDrive series, an investigative article on ReadWrite.com asks what will happen to drivers' spare time in the car when they no longer need to take the wheel.

The estimated hour per day that Americans spend driving is "just about the only time we don't have our eyes glued to screens," ReadWrite noted.

If the Google car is doing the driving, at least some of motorists will be using online media and viewing Google ads.

Self-driving cars may have a lower margin of error, but autonomous technology could be extraordinarily invasive as it takes in such personal information as the places people frequently visit or their current locations.

"What does bother me is how Google, once it has us in its vehicles, will 'optimize' our in-car experiences," ReadWrite.com's Bradley Berman wrote.

The tech behemoth already holds digital information including web searches, media consumption, email content, social networks and more. Google's Street View vehicles, which gather images of neighborhoods through satellite and GPS, were intercepting personal online data in 2010. What will be the next step with self-driving Google cars?

"We are being told how cool it will be to type our desired location into the self-driving car's navigation system, take our foot off the brake and let go of the wheel.  What could go wrong?" Berman asked.

Autonomous driving opens up opportunities for government surveillance and hacking. Berman also points out that Google's proposed self-driving fleet of rental cars could take motorists on the drive that is most profitable to the company.

As self-driving cars get closer to the mainstream market and people put more personal data online, many have raised concerns about privacy and safety issues.

Massachusetts Sen. Edward Markey recently sent an open letter to 20 automakers asking them to address their vehicles' vulnerability to hacking.

Google and several other tech companies have also joined the refrain for more online privacy by sending a letter to Washington in the wake of the notorious NSA leak.

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