More than 20 driverless vehicles in Arizona have reportedly been vandalized in the last two years.

As the prominence of self-driving cars grows in Waymo’s test market of Chandler, Ariz., a city near Phoenix, so do attacks on the vehicles, according to The New York Times.

The attacks include the slashing of tires of Waymo vans, which are owned by Google’s parent company, and rocks being thrown at the vehicles, according to police reports reviewed by the Times.

ADVERTISEMENT

Tempers have flared at the self-driving vehicles since a pedestrian in Arizona was killed by a self-driving Uber car last year.

“There are other places they can test,” Arizona resident Erik O’Polka told the the Times. “They said they need real-world examples, but I don’t want to be their real-world mistake.”

O’Polka was issued a warning by police last month after they received multiple reports that he was attempting to run Waymo vehicles off the road.

All Waymo vehicles still have a driver in them in case of emergencies, but the Times reports that Waymo has been reluctant to provide video of attacks on the cars.

In one case, a Waymo employee told police they would need a warrant in order to get video.

A Waymo spokeswoman told the Times that the attacks on the company’s vehicles make up only a small fraction of the total miles the cars cover in Arizona.

“Safety is the core of everything we do, which means that keeping our drivers, our riders, and the public safe is our top priority,” Waymo spokeswoman Alexis Georgeson said. “Over the past two years, we've found Arizonans to be welcoming and excited by the potential of this technology to make our roads safer.”

Arizona’s hands-off approach to regulations on the emerging industry and consistently good weather have helped make it a popular location for self-driving car testing.