Google’s self-driving cars roaming through the roads of Mountain View and Texas for test runs have been involved in some fender benders, but distracted drivers were the ones who rear ended the cars.

Still, there’s also been about a dozen times when the self-driving cars have come close to hitting an object, prompting a driver to take over, a report released Tuesday by the tech firm showed.

From Sept. 24, 2014 to Nov. 30, 2015, the car’s software handed over the control of the vehicle to test drivers 272 times because the system detected a glitch, such as a broken wire or problems with sensors that track location or how fast the car is going, according to the report.

During that same period, a test driver took over 69 times because of safety concerns. In 13 of those incidents, the test drivers prevented the car from hitting an object, Google’s data showed.

The majority of these incidents happened because the car’s sensors were not correctly perceiving an object such as an overhanging branch as an obstacle or a software glitch.

Chris Urmson, who heads Google’s self-driving car program, noted though in a blog post on Tuesday that the rate of those incidents have been declining and the company has made progress.

“Thanks to all this testing, we can develop measurable confidence in our abilities in various environments,” he wrote. “This stands in contrast to the hazy variability we accept in experienced human drivers — never mind the 16-year-olds we send onto the streets to learn amidst the rest of us.”

But as the California Department of Motor Vehicles considers draft rules for the use of autonomous cars some advocacy groups point to Google’s latest data as evidence that the vehicles aren’t ready for the public roads without a driver. The state agency released draft rules in December that would require a licensed driver be in an autonomous car, an idea Google disagreed with because the technology was developed in part to help people who can’t drive, such as the disabled and elderly.

“The DMV got it exactly right and is putting our safety first,” said John M. Simpson, Consumer Watchdog’s Privacy Project director in a statement.  “How can Google propose a car with no steering wheel, brakes or driver when its own tests show that over 15 months the robot technology failed and handed control to the driver 272 times and a test driver felt compelled to intervene 69 times?”

Test drivers responded swiftly in those incidents and on average took control of the self-driving vehicle in less than a second, the report showed.

The self-driving cars have operated autonomously for more than 1.3 million miles as of November and 424,331 of those miles were driven on public roads.

Other auto manufacturers who are testing driverless cars such as Mercedes Benz, Tesla and Nissan are also expected to submit similar data to the DMV.