Questions and answers about new self-driving car safety data

“The timing of Nissan’s on-road autonomous vehicle testing sessions was as planned and consistent with our autonomous vehicle development schedule”, company spokesman Steve Yaeger wrote in an email.

Eleven manufacturers are now testing autonomous vehicles on the state’s roads, seven of which (VW/Audi, Mercedes Benz, Google, Delphi Automotive, Tesla Motors, Bosch, and Nissan) were required to submit their first disengagement reports by 1 January 2016.

Google’s disengagement report, which covers more vehicles and miles driven than any of the others, notes that 272 out of 341 disengagements were related to “a failure of the autonomous technology” – a category that includes broken wires, anomalies coming in from sensor readings, or anomalies in operations like steering and braking.

Google’s fleet of self-driving cars consists of 53 vehicles, the largest fleet of autonomous cars in the country.

Google acknowledged that in 11 of the 341 cases reported to the DMV the situation would have resulted in a crash if a human driver hadn’t taken the wheel. The Guardian points out that Google actually says that its drivers took over “many thousands of times”, but “the company is reporting only 69 incidents because Google thinks California’s regulations require it to only report disengagements where drivers were justified in taking over, and not those where the vehicle would have coped on its own”.

The filed report also showed the number of disengagements declining significantly during the test period. Delphi reported 405 disengagement over 16,662 miles, while Nissan reported 106 over 1485 miles. It was worked out via computer simulations that in 13 of the driver-initiated interventions, a crash would have followed had the driver not taken control. But it’s showing improvement.

Google also offered explanations as to what anomalies triggered the disengagement. The numbers only reflect miles driven on California roads and disengagements that happen in that state.

There were also 69 times where drivers chose to take control for “reasons relating to the comfort of the ride, safety of the vehicle, or the erratic or unpredictable behaviour of other road users”. “Rather it is to gather, while operating safely, as much data as possible to enable us to improve our self-driving system”. Other reports were not almost as descriptive. The company itself decides which manual disengagements were justified and which were not by replaying each disengagement in an online simulator.

Delphi even broke down the causes (PDF) for disengagement in a table.

As of September, Google’s fleet of more than 20 self-driving vehicles and its team of safety drivers have logged about 1.7 million miles – manually and autonomously.

Google released its report Tuesday before the agency posted reports from other companies in what Google described as an effort to be transparent about its safety record.

LOS ANGELES -Futuristic self-driving cars travelling along California roads have needed plenty of old-fashioned human intervention to stay safe.