A self-driving Uber car struck 49-year-old Elaine Herzberg as she walked her bicycle across a street in Tempe, Arizona on Sunday night. The woman passed away.

The Volvo XC90 was in autonomous mode, and Rafael Vasquez, 44, was behind the wheel as a safeguard as the vehicle piloted itself. The SUV was moving around 65 km/h (40 mph) in a 35 mph zone, according to Tempe Police detective Lily Duran. Police said that there were no significant signs of the SUV slowing down before the crash.

Apparently, Herzberg, who may have been homeless according to the police, was crossing the street mid-block when she was struck. “The safety of our citizens here in Tempe is of the utmost importance. None of us ever want to go through this ever again, using the crosswalks will definitely limit this from happening again,” Tempe Police Sgt. Ronald Elcock said.

Uber, which is conducting autonomous vehicle tests in Arizona, Pittsburgh, Toronto and other areas, said it has stopped testing the vehicles throughout North America after the fatal crash.

“Our hearts go out to the victim’s family. We’re fully cooperating with police and local authorities as they investigate this incident,” Uber said in a statement. “Some incredibly sad news out of Arizona. We’re thinking of the victim’s family as we work with local law enforcement to understand what happened,” Uber CEO Dara Khosrowshahi tweeted.

Needless to say, pedestrians and cyclists are among the biggest challenges for autonomous cars. Uber recently constructed a ‘fake city’ for the testing of its autonomous cars. Called Almono, the 42-acre facility contains obstacles including roadways, complicated intersections, fake cars and unpredictable pedestrians.

In the real world, Arizona is the main testing ground for self-driving cars. According to CNN, earlier this month, Arizona governor Doug Ducey updated an executive order to allow autonomous cars to drive on state roads without a test driver behind the wheel, which is the current norm.

Waymo, the self-driving arm of Google’s parent company Alphabet, is launching a public self-driving car service this year in the state’s Phoenix area. Others such as GM’s Cruise and Intel are also present in Arizona, which does not have much rain or snow to disrupt the navigation of the self-driving machines. What’s your view on autonomous cars?