Waymo on Wednesday said it has raised $2.5 billion from parent-company Alphabet and others in a new funding round to fuel its mission of getting self-driving cars on the road.

The infusion of cash comes just months after the departure of Waymo chief John Krafcik prompted concerns that the unit might be stuck in low gear despite boasts of gaining traction.

Waymo is among several automotive and tech firms testing autonomous driving, although no large-scale deployments have begun.

The latest funding will be used to improve Waymo autonomous driving technology and build the company's team, according to co-chiefs Tekedra Mawakana and Dmitri Dolgov

"We agree with those experts who say there's no greater challenge in artificial intelligence than building and deploying fully autonomous technology at scale," Dolgov and Mawakana said in a release.

"We're grateful to our investors for believing in this mission, in our technology, and in us."

Investors taking part in the latest funding round included Alphabet and venture capital titan Andreessen Horowitz, according to Waymo.

Waymo earlier this year began testing its driverless ride-hailing service on the streets of San Francisco with employees as riders.

The move expanded on "robo-taxi" testing be done by Waymo in the Phoenix, Arizona area in recent years.

"We're the first and only company operating a fully autonomous, public, commercial ride-hailing service — Waymo One — and have served thousands of riders in Metro Phoenix," Dolgov and Mawakana said.

Waymo is also working with Daimler Trucks and others to put self-driving technology to work moving commercial goods, according to the co-chiefs.

Waymo last year raised some $3 billion from investors and has yet to turn a profit.