Google's self-driving car project, now called Waymo, made some big strides during 2016, according to a report from the company published by the California Department of Motor Vehicles.
California requires would-be self-driving car manufacturers to apply to the state's autonomous vehicle testing program and submit regular reports if they want to test their cars on public roads in the state. Several companies participate, including major car brands, suppliers, and hopefuls. Waymo has been submitting reports since at least 2015.
The report published Wednesday lists the number of times a driver had to take over for the autonomous system while driving — these are known as disengagements. Waymo's total number of disengagements per 1,000 miles of driving went from 0.8 in 2015 to 0.2 in 2016 — a precipitous drop.
Most of these disengagements are not accidents, but they often represent times when a driver would have had to shut the system down to make some kind of fix. The drop in disengages shows that drivers need to interrupt the system less often — in other words, the company is refining the technology.
Waymo's self-driving technology head, Dmitri Dolgov, said in a blog post Wednesday that the company has 2.5 million miles of autonomous driving on public roads, and that Waymo has "been able to make dramatic improvements to our technology because we use each of these disengages to teach and refine our car," noting that the new disengagement numbers represent a four-fold improvement over the previous year.
But its drop in disengagements suggests the Alphabet unit is improving its system. Dolgov noted that Waymo does most of its testing in "complex" environments, such as busy city streets, or near construction zones. This is by design: Waymo is trying to replicate the sorts of environments actual drivers are likely to encounter.
Ten companies in total submitted disengagement reports for 2016, including Tesla, which briefly ran some tests in October of last year. It is worth noting that while Tesla's participation is limited, the company tests its (not fully autonomous) Autopilot driver assistance system in other ways, such as drawing on customer data, and testing cars at private facilities.