(Reuters) – Fully automated driverless cars could make up nearly 10% of global vehicle sales, or about 12 million cars a year, by 2035, the Boston Consulting Group said on Thursday.

BCG said 44 percent of U.S. drivers it surveyed would consider buying a fully autonomous vehicle within the next 10 years, and that 20 percent would be willing to pay an extra $5,000 or more for the advanced technology required to operate such a vehicle.

“This will be as radical a change as the auto industry has seen in 100 years,” said Thomas Dauner, head of BCG’s global automotive practice.

Vehicle manufacturers, including General Motors GM , Volkswagen AG’s Audi and Daimler AG’s Mercedes-Benz, already are working on semi-automated systems that will still require some human involvement.

The first such systems, which will automatically control steering, braking and throttle in certain situations, are being phased in this year and next. They will appear initially in such premium cars as the 2016 Cadillac CT6 and the 2017 Audi A8.

But it will be a long, slow ramp-up from semi-automated systems to fully self-driving cars, according to the vehicle manufacturers, many of which expect that the first truly autonomous cars will not reach the market until 2025.

Enhanced safety is one of the key factors attracting consumers to automated cars, BCG said, but also the ability to perform tasks other than driving while in the car. Lower insurance and fuel costs also were cited.

Manufacturers and suppliers are rapidly rolling out new hardware designed to speed adaptation of self-driving systems.

At this week’s Consumer Electronics Show in Las Vegas, Mercedes-Benz, Audi and BMW showed vehicles with various autonomous capabilities.

Daimler’s chief executive, Dieter Zetsche, and Audi’s chief technology officer, Ulrich Hackenberg, said they expect various autonomous systems to be rolled out in stages over the next five to 10 years.

As part of its study, BCG said it expected so-called autopilot systems that assist with parking and negotiating traffic jams to begin appearing in two years, followed in 2018 by a highway autopilot system with automated lane-changing capability.

Farther down the road, fully driverless vehicles, including “robo-taxis,” could prompt a dramatic shift in urban driving, with more car sharing helping to reduce traffic density, pollution and fuel consumption.

Twenty years from now, “people will not own cars in large cities,” thanks to widespread adoption of autonomous vehicles, said BCG’s Xavier Mosquet.