Bill Gates says totally driverless cars, without need for even a steering wheel, are "coming sooner rather than later."

The tech billionaire and Microsoft co-founder recently took a "test ride" in an autonomous vehicle through the busy streets of downtown London, which he described in a blog post on Wednesday as "one of the most challenging driving environments imaginable."

Gates' verdict: It was "a memorable ride," and "it was a bit surreal to be in the car as it dodged all the traffic." The trip included a safety driver who took control of the car multiple times, he noted.

He also posted a video of his experience:

The car's technology was built by British startup Wayve, which partners with Microsoft on its artificial intelligence-based autonomous driving software. The 6-year-old startup has raised more than $250 million from investors including Microsoft, billionaire Virgin Group co-founder Richard Branson and Meta chief AI scientist Yann LeCun.

Wayve sits among a bevy of tech and auto industry competitors: The likes of Ford, GM, Tesla, Alphabet and China's Baidu have invested billions of dollars toward developing their own driverless vehicle technology.

As the technology moves forward, the cars could be good for both your wallet and the planet, Gates argued: Autonomous vehicles may eventually become cheaper than regular cars, and most of them will probably be electric.

"They'll even help us avoid a climate disaster," he wrote.

Currently, even the most advanced autonomous vehicles require a driver who can only take their hands off the steering wheel in certain situations on the road, and need to always be ready to reassume control. The next step, where the driver can cede most control to the vehicle, is coming within the next decade, Gates wrote.

That doesn't necessarily mean this year, or even next year. Elon Musk's self-driving push at Tesla, for example, has hit enough obstacles and delays for one former employee to say the company is "nowhere close" to perfecting its technology, the Washington Post reported earlier this month.

Consumer cars also won't be the first, second or even third type of fully self-driving vehicles on public roads, Gates wrote: It'll start with long-haul trucking and delivery vehicles, before moving to robotaxis or rental cars and ride-shares.

U.S. consumers will likely only gain access to fully self-driving vehicles following a complete overhaul of the nation's driving infrastructure and laws, he added.

Last year, U.S. regulators cleared the way for autonomous cars built without steering wheels or even pedals — a first step. And in January, consulting firm McKinsey predicted that by 2035, roughly 37% of new passenger cars sold will feature "advanced" autonomous driving technology, where cars can handle most driving situations on their own without drivers taking control.

By that point, the self-driving car industry will bring in up to $400 billion in revenue annually, McKinsey predicted.

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