Alphabet Inc.’s Waymo is launching a new account type that lets teenagers hail a robotaxi and ride alone, expanding its rider base while continuing to test its service in more US cities.

Waymo has introduced an option for teen accounts, allowing young passengers to take rides in its driverless robotaxis without adult supervision. The program is only available in metropolitan Phoenix for now, but the company said it plans to offer the service in other cities down the line.

Waymo said it will offer “specially-trained Rider Support agents” during rides hailed by teens and loop in parents if needed.