[Talk-us] Prima Facie Speed Limits

Martijn van Exel m at rtijn.org
Tue Sep 9 20:17:02 UTC 2014


Agreed - that's a pretty small use case, relatively, though.

On Tue, Sep 9, 2014 at 1:38 PM, Tod Fitch <tod at fitchdesign.com> wrote:

> Historical and live speed profiles are pretty much required for trip
> planning in congested urban areas, but for those of us who drive close to
> the speed limit and make long trips on relatively uncrowded rural freeways,
> travel time estimates based on posted (or prima facie) speeds are a good
> approximation to reality. I travel between northern California and southern
> Arizona a lot. The distance is about 1,300 kilometers and only a small
> fraction of that is congested urban freeways (especially if I decide, as I
> usually do, to avoid Los Angeles). OsmAnd with its knowledge of actual
> posted speed limits (many entered by me) does a very good job at predicting
> my arrival time.
>
> On Sep 9, 2014, at 11:48 AM, Martijn van Exel wrote:
>
> > There's a functional difference between speed limits and the actual
> speed driven. For ETA prediction, speed limit data is not all that useful -
> detailed historical and live speed profiles are. That is not data that is
> in OSM (or should be). The speed limits are mostly useful for alerting
> drivers they may be driving too fast. For a system like that to be feasible
> you will need comprehensive posted speed limit coverage, which OSM
> currently does not have.
> >
> > Martijn
> >
>
>
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