
Using Metromile data to determine a car's gear ratios - jeffonabike
https://whatsyourpvalue.wordpress.com/2016/09/22/a-party-trick-with-metromile-data/
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ilikeatari
Great article! The gear ratio data would be useful to potentially derive more
granular driver behavior model (acceleration) that is less mass dependent than
accelerometer sensor. However, I do wonder if there is a way to determine the
usage of the reverse gear itself. This data is currently not universally
available via OBDII. The reverse gear data would be very useful since large
amount of accidents are backing accidents.

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nickff
From the data provided, it seems likely that OBD is reporting any speed while
reversing as 0, so you could probably guess that when the engine speed is
changing slowly (while above idle), and OBD reports vehicle speed as 0, the
car is reversing.

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jeffonabike
This may be true - but even if the sensor is reading zero vehicle speed and
greater than idling engine speed, it's difficult to assume these are in fact
reverse and aren't just "engine revving" moments. Looking into a time-series
breakdown of each moment - seeing if the engine speed is 'changing slowly' as
you mention - would be key in properly identifying Reversing vs. Revving.

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nickff
This is why I specified engine revving slowly; engines which are disconnected
from the drivetrain tend to rev up very quickly. In addition, cars with
automatic transmissions are a majority of the US fleet, and spend very little
time in neutral.

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hammock
> engines which are disconnected from the drivetrain tend to rev up very
> quickly

So do engines which are in reverse and being controlled by drivers who are
imminently about to have an accident :)

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hammock
What does this look like for a car with continuous variable transmission, like
a late model Nissan Altima?

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hydrogen18
Most cars with a CVT are configured from the factory to have "gears". Even
though the transmission is continuously variable, it is made to quickly move
between distinct ratios. This is mostly because with a true CVT acceleration
is very smooth and difficult for the customer to perceive.

So the graph looks almost identical.

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NikolaNovak
This is fascinating:

    
    
       This is mostly because with a true CVT acceleration is very smooth and difficult for the customer to perceive.
    

Can you provide any more insight or further reading? I am considering a CVT
(Subaru XT), and smooth acceleration without jumps is precisely what I would
be looking for (which I believe was provided by my Scooter with a CVT as
well).

If companies are adding artificial jerks to a technology that is designer for
smooth experience, I'm not sure whether i'd laugh or cry, but I feel I'd like
to know more :-/

Thanks!

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beamatronic
>> I'm not sure whether i'd laugh or cry

Exactly... for me it's the same with electric cars that make fake engine
noises. But that one I grudgingly accept, in parking lots, for safety reasons.

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bunderbunder
I'm pretty OK with electric cars making fake engine noises. The Prius owner in
my neighborhood would be semi regularly creaming people if they didn't have
any auditory indication that he was about to come cruising out of the alley
without slowing down to check for pedestrians.

It doesn't _have_ to be engine noises, it could be playing some sort of crazy
"woop woop woop" sound for all I care, but I'm guessing the owner would prefer
it be something a bit less embarrassing.

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honkhonkpants
130 km/h is a pretty good clip. Does Metromile charge clients more for high
speeds?

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iav
California prohibits pricing based on driving habits like speed. Other states
do permit it and Progressive offers snapshot device which does what you
describe - offer discounts for safe driving behavior.

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honkhonkpants
Wow really, that is amazing and unsurprising at once. I can only imagine the
debate that led to this regulation.

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querious
Actually a pretty good way to understand manual transmission. Very cool.

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frankus
It would be neat if you could enter a tire size (e.g. 165-65R13) and estimate
the overall diameter from that.

Extra credit: figure out a plausible count of gear teeth for each ratio.

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Sundog
Neat

