Self-driving technology start-up Waymo has received the green light from California regulators for its self-driving cars to start carrying people. 

The state's Public Utilities Commission gave the nod to Waymo, a unit of Alphabet  (GOOGL) - Get Report  , to participate in California's Autonomous Vehicle Passenger Service pilot program, though it is not allowed charge riders, and an operator must be behind the wheel.

The three-year permit is separate from one allowing companies to test self-driving cars in the state. Some 60 companies have received approval from the California Department of Motor Vehicles for that type of service. 

Waymo is the fourth autonomous-vehicle company to participate in the California program, along with Zoox, Autox Technologies and Pony.ai. The company is already offering an autonomous taxi to volunteer testers in the Phoenix area.

The company has also made its autonomous service available on a trial basis to Lyft (LYFT) - Get Report riders in the Phoenix area, though again those cars must have a human being behind the wheel. 

Shares of Alphabet were up 0.31% at $1,116.01 in early trading on the Nasdaq Stock Market. 

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