Alphabet Inc.'s (GOOGL) - Get Report  Waymo launched a self-driving taxi service in the Phoenix area on Wednesday.

Waymo One is a 24-hour driverless vehicle service operating in a roughly 100-mile zone in the Phoenix suburbs of Chandler, Tempe, Mesa and Gilbert. Waymo has been testing its technology in that area since 2016.

Riders must download an app and provide a credit card number, which is similar to ride-sharing services Uber and Lyft. A human driver will be behind the wheel to intervene in case of an emergency.

Riders will see price estimates before they accept the trip based on factors like the time and distance to their destination, Waymo said in a company blog post. They can contact customer support through an in-car console or through the Waymo app to ask questions. 

"These channels will become even more important as we transition to fully driverless rides," Waymo said.

Up to three adults and a child can ride in the vehicle.

CEO John Krafcik said in a blog post Wednesday that Waymo first started inviting people to ride in the self-driving vehicles in April 2017 through an early rider program.

"We'll first offer Waymo One to hundreds of early riders who have already been using our technology," Krafcik wrote. "Over time, we hope to make Waymo One available to even more members of the public as we add vehicles and drive in more places."

Alphabet, Google's parent company, also operates Wing, a drone delivery business, which said Tuesday that it was introducing service in the Helsinki, Finland, area. Wing spent 18 months testing drone deliveries in southeastern Australia, partnering with local businesses to deliver food, drinks, medicine and household items.

Shares of Alphabet Inc. closed down 5.03% Tuesday to $1,050.82.

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