California’s Department of Motor Vehicles released its annual autonomous vehicle disengagement report today, in which all the companies that are actively testing self-driving cars on public roads in the Golden State disclose the number of times that human drivers were forced to take control of their driverless vehicles. The biggest news to come out of this report is from Waymo, Google’s new self-driving car company, which reported a huge drop in disengagements in 2016 despite an almost equally huge increase in the number of miles driven.

In other words, Waymo’s self-driving cars are failing at a much lower rate, even as they are driving a whole lot more miles. The company says that since 2015, its rate of safety-related disengages has fallen from 0.8 per thousand miles to 0.2 per thousand miles in 2016. So while Waymo increased its driving by 50 percent in the state — racking up a total of 635,868 miles — the company’s total number of reportable disengages fell from 341 in 2015 to 124.

“This four-fold improvement reflects the significant work we’ve been doing to make our software and hardware more capable and mature,” Dmitri Dolgov, head of self-driving technology for Waymo, wrote in a blog post. “And because we’re creating a self-driving car that can take you from door to door, almost all our time has been spent on complex urban or suburban streets. This has given us valuable experience sharing the road safely with pedestrians and cyclists, and practicing advanced maneuvers such as making unprotected left turns and traversing multi-lane intersections.”

The majority of Waymo’s disengagements were the result of “software glitches,” the company says. “Unwanted maneuvers,” “perception discrepancies,” and “recklessly behaving road user” also accounted for dozens of disengagements. There were no reports of crashes or accidents.

California requires companies that want to test autonomous vehicles on the roads to register for an autonomous driving permit. As part of this program, companies are also required to report their disengagement rates to the DMV, which then makes those numbers public. This requirement was likely a factor in Uber’s refusal to obtain an autonomous permit, resulting in the DMV revoking the ride-hail company’s vehicle registration for its self-driving cars.

Waymo is miles ahead of its competitors in public testing. While a host of car and tech companies have been testing for many years privately, Waymo still has the edge on real-world experience. Also, the news of the improvements in Waymo’s self-driving technology comes just as the company plans to deploy its fleet of autonomous Chrysler Pacifica minivans, which it first debuted at the Detroit auto show last month. The vans will hit the road in Mountain View, CA, and Phoenix, AZ, sometime in the next few days.