Uber's testing with autonomous cars has been a little bumpy

Thanks to having more cars driving more miles in more areas, the total number of autonomous miles is creeping up, but the metric that Uber uses to measure just how autonomously the cars can drive is creeping up somewhat more slowly.

Travis Kalanick has described self-driving technology as "existential" to Uber's future as a company.

Last week was the second time since December 2016 when Uber's cars were driven more than 20,000 miles in a week in "driverless" mode. With a human behind the wheel to take over as needed, Uber's autonomous fleet managed to rack up a bit over 1,000 rides per week with semi-autonomous operation.

Beyond self-driving cars, Uber has long-term ambitions to develop a fleet of autonomous flying vehicles.

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Recode reports that the company's 43 active self-driving cars in Pennsylvania, Arizona, and California logged 20,354 autonomous miles last week. A more important figure is the number of miles between what Uber calls "critical" interventions on the driver's part-situations where if a driver hadn't stepped in, a person might have been injured or at least $5,000 worth of property damage could've occurred. For critical interventions, meaning when a driver has to take over to avoid harmful events, cars averaged 200 miles between incidents. One of the first major breakthroughs was in 2012, when Italian company VisLab built a self-driving auto that negotiated two-way narrow rural roads, traffic lights, pedestrian crossings, speed bumps, pedestrian areas, and tight roundabouts for twenty minutes without any intervention.

The human had to stop the vehicle from hitting pedestrians or property - or to better control jerky steering or hard braking that made customers uncomfortable, the Uber data revealed. But Uber testers didn't see a steady rate of progress either, since the average seems to dip and rise back up. In January, cars could go four miles without this type of experiences; this dropped to an average of two miles in the week ending 8 March.

Bryant Walker Smith, a member of the Advisory Committee on Automation in Transportation that was set up by the U.S. Department of Transportation, told BuzzFeed that to be able to deploy self-driving vehicles without human drivers, Uber will need to come up with metrics that are far better than what have been reported.