Google’s self-driving car project Waymo is launching its new commercial self-driving service today in the Phoenix metro area to hundreds of select early riders.

Invites to join the service, dubbed Waymo One, will go out today. It will serve Chandler, Tempe, Mesa, and Gilbert. It is unknown when the general public will get a chance to use the service.

Pricing will be based on distance and time of each trip, along with other factors. No other specifics about pricing were released. Riders will see price estimates before they accept a trip.

During the ride, passengers will see key details of their trip on an in-car console and screen, as well as on the app. Riders also can connect to a support agent for any questions, according to Waymo.

“These channels will become even more important as we transition to fully driverless rides,” according to a Waymo statement. “At the start, Waymo-trained drivers will be riding along to supervise our vehicles for riders’ comfort and convenience.”

Up to three adults and a child can ride in each trip to share in the experience. Riders will be asked to provide feedback on trips to help the service, according to Mountain View, California-based Waymo.

Google started the project almost 10 years ago to explore how best to use self-driving technology to make roads safer and easier to navigate, said CEO John Krafcik.

“We’ve been focused on building the world’s most experienced driver ever since,” Krafcik said in a statement.

Waymo’s vehicles have self-driven 10 million miles on public roads, with 7 billion miles driven in the simulation.

More than 400 people have taken rides in Waymo cars since April 2017, when the company first invited the public to ride in its initial program. This group has given feedback to Waymo’s product and research teams during trips to and from home, work, school, and shopping.

“Their feedback along the way has helped us refine our technology and design features that meet their needs,” Krafcik said. “Based on their comments, we worked on ways to streamline pickups, to contact support for questions, and to get around town at all times of the day.”

Eventually, Waymo One will expand to more people as additional vehicles are added and Waymo drives in more areas of the Valley.

“Self-driving technology is new to many, so we’re proceeding carefully with the comfort and convenience of our riders in mind,” Krafcik said. “At first, Waymo-trained drivers will supervise our Waymo One vehicles.”

Some early riders have experienced driverless rides, according to the company.