During the National Governors Association conference on Friday, July 20, Waymo’s CEO John Krafcik announced that the company’s self-driving cars have reached eight million miles driven on public roads, translating into roughly 25,000 miles driven every day.

Last November, Waymo announced that it had driven four million miles on public roads, meaning that the company has doubled that number in just eight months.

Additionally, Krafcik noted that Waymo has also “driven” five billion miles in simulation. The simulator allows self-driving cars to practice situations they may not regularly run into in the real world, giving Waymo’s engineers the opportunity to run their virtual vehicles through “edge case” scenarios over and over to build important training data that then gets fed back into the machine learning software.

With plans on launching the world’s first self-driving transportation service later this year, Waymo currently has more than 400 residents of Chandler, Arizona as part of its Early Rider program. Waymo says that it is adding more people every day and expects to kick off its paid taxi service later this year.

Even with Waymo’s ambitious outlook, though, Krafcik noted during the conference that the mass adoption of autonomous vehicles will probably be “longer than you think,” pointing out that there are no fully autonomous vehicles available for purchase today, and might not be for years to come.

“There are no autonomous systems available, zero on the road today,” Krafcik said via the Verge.

“Anything you can buy on the road today is a driver assist system, that means the driver is completely responsible for the car and I think there is so much confusion on that.”

Yet and still, that has not stopped Waymo from testing its technology, as the company has more than 600 self-driving Chrysler Pacifica minivans operating on public roads. And just a few months ago, Fiat Chrysler Automobiles (FCA) and Waymo announced the expansion of their partnership, with an agreement to add up to 62,000 Chrysler Pacifica Hybrid minivans to Waymo’s self-driving fleet.