California releases report on Waymo autonomous-vehicle disengagements

Feb. 2, 2017

The California Department of Motor Vehicles has released a report from Waymo regarding autonomous-vehicle disengagements experienced by self-driving cars operating on California roads.

Waymo reports that as of the reporting period from December 2015 through November 2016, it had operated its self-driving cars in autonomous mode for 635,860 miles on public roads in California, most on surface streets in Mountain View and neighboring communities. Waymo said that represents 50% more autonomous driving miles that the previous reporting period.

Waymo said, “Disengagements are a natural part of the testing process that allow our engineers to expand the software’s capabilities and identify areas of improvement. During testing our objective is not to minimize disengagements; rather, it is to gather, while operating safely, as much data as possible to enable us to improve our self-driving system. Therefore, we set disengagement thresholds conservatively, and each is carefully recorded.”

Overall, disengagements in the 2016 period fell to 0.2 per 1,000 miles from 0.8 per 1,000 miles in the previous reporting period.

Out of a total of 124 disengagements, Waymo reports, 51 disengagements occurred because of a “software discrepancy,” and 30 for “unwanted vehicle behavior.” Others, in descending order, occurred because of a “perception discrepancy,” a “recklessly behaving road user,” and “incorrect behavior prediction of other traffic participants.” Two disengagements each were reported for encountering a construction zone, an emergency vehicle, and roadway debris. Unsurprisingly for California, only one disengagement was due to weather.

The cars did well on interstate highways and freeways with no disengagements. Disengagements totaled 112 for the reported “street” category.

You can read the complete report here.

Tim Higgins at The Wall Street Journal reports that 21 companies have permits to test self-driving cars on California roads, but many just received them and won’t be required to report until later. The other companies are far behind Waymo. Higgins reports that Cruise Automation, acquired by GM last year, had the second largest number of miles of autonomous operation at about 10,000 on California roadways, with a disengagement rate of 18.51 per 1,000 miles.

And finally, Uber tried to test self-driving cars in California but—losing an argument that it didn’t need to get permits—moved its tests to Arizona.

Update, February 9: Commenters have asked what happens when the vehicle disengages. In most cases the driver takes manual control. Here’s what the report has to say:

“As part of testing, our cars switch in and out of autonomous mode many times a day. These disengagements number in the many thousands on an annual basis though the vast majority are considered routine and not related to safety. Safety is our highest priority and Waymo test drivers are trained to take manual control in a multitude of situations, not only when safe operation ‘requires’ that they do so. Our drivers err on the side of caution and take manual control if they have any doubt about the safety of continuing in autonomous mode (for example, due to the behavior of the SDC or any other vehicle, pedestrian, or cyclist nearby), or in situations where other concerns may warrant manual control, such as improving ride comfort or smoothing traffic flow. Similarly, the SDC’s computer hands over control to the driver in many situations that do not involve a ‘failure of the autonomous technology’ and do not require an immediate takeover of control by the driver.”

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