Police Say Uber Is Likely Not at Fault for Self-Driving Car Fatality in Arizona

Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by bichiliad on Monday March 19, 2018 @09:48PM (#16625306)

This is probably less the case with self-driving cars, as I imagine they're using pretty new or well-maintained vehicles, but there's usually a 5mph leeway with speed limits due to slightly mis-calibrated speedometers. I anecdotally remember hearing this being the reason for speed limits that end in "5" rather than being multiples of 10.

https://travel.stackexchange.com/questions/40113/do-any-stat...

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by majormajor on Tuesday March 20, 2018 @12:31AM (#16626082)

Nowdays its much more electronic than it used to be, so speedometers are much more consistent than they used to be.

The way speedometers used to work is pretty interesting: http://www.explainthatstuff.com/how-speedometer-works.html

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by protomyth on Monday March 19, 2018 @10:27PM (#16625516)

Wouldn’t that be mitigated by the GPS and the map? It would seem that an automated car using maps as an important input would no its exact position and therefore speed.

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by __david__ on Monday March 19, 2018 @11:45PM (#16625889)

GPS can be remarkably bad in urban environments. You can't really trust it for second-to-second speed or positioning. It's only really good for long term/high level planning. For speed, the wheel sensors are going to be way more reliable and consistent.

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by asteli on Tuesday March 20, 2018 @12:54AM (#16626150)

The typical approach is to fuse GPS, inertial, and wheelspeed sensors to track a vehicle's motion in space. They all have their shortcomings, and all compensate for each other.

GPS is, as you said, wildly inaccurate, disconcertingly often. Wheelspeed is great when you're moving, but at low speed it tends not to have the granularity you want. Inertial sensors are pretty amazing nowadays, but they still drift.

To illustrate, if your wheels aren't moving, then you can ignore the IMU telling you that you're sinking into the ground at 5mm/s. Watching the monitor of a mapping vehicle as it depicts the car returning to mother Earth is pretty hysterical though. Until you have to fix it.

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by ygra on Tuesday March 20, 2018 @06:51AM (#16627375)

Actually, with a good receiver you can use GPS for very precise speed measurements by using the doppler shift of the carrier signal. It's just that most receivers don't give you access to that so the only other option is using the current and previous position and the timings of them.

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Re:Police Say Uber Is Likely Not at Fault for Self-Driving C... by bichiliad on Monday March 19, 2018 @11:34PM (#16625844)

That could easily be the case, sure. Some other people mentioned that it could be just to more closely emulate a human driver. I don't think we'll have a good answer without knowing the implementation.

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