(Reuters) - Alphabet's Waymo said on Tuesday its autonomous ride-hailing service, Waymo One, is now available to everyone in San Francisco, nearly four years after a similar move in Phoenix, Arizona.

Driverless vehicles are expected to drive commercial success for automakers even as regulatory scrutiny remains tight amid concerns of investors about growing investments in the nascent technology.

Waymo had started a test service with its research-focused program in San Francisco in 2021, which included an autonomous specialist on board for all rides at that time, as it looked to commercialize the technology.

The company said that about 300,000 people had signed up to ride with Waymo since it first opened a waitlist in the city, signaling strong demand. Now with open access, anyone can request a ride on its app.

The company had opened access to everyone in Phoenix, Arizona without a waitlist in 2020.

Mountain View, California-based Waymo is a self-driving technology pioneer, which started its first U.S. driverless taxi service in 2020 over a decade after it was born in 2009 as a project inside Google.

In March, the company received approval from the California Public Utilities Commission (CPUC) to start its Waymo One in Los Angeles and some cities near San Francisco.

Rivals including General Motors-backed Cruise and Amazon.com's Zoox are accelerating a race to succeed amid probes by auto regulators involving the performance of autonomous driving cars.

Last month, the U.S. National Highway Traffic Safety Administration said it had learned of nine additional incidents raising concerns about the performance of Waymo self-driving vehicles.