[Talk-us] Prima Facie Speed Limits

Tod Fitch tod at fitchdesign.com
Tue Sep 9 21:00:26 UTC 2014

Yes, a "pretty small use case" at somewhere around 10,000,000 trips per year on I-5 through the central valley of California. Or 9,000,000 trips per year each way on I-8 across the desert to the Arizona border.

On your daily commute, you may not need help navigating so much as you want accurate real time information about which routes are moving well compared to others. For me, trip planning and using a navigation device is not for local driving (I mostly use OsmAnd for local driving to help me find errors in OSM data) as much as for getting me to places I don't go on a daily basis. You could say it is a pretty small use case as most people don't drive to or through unfamiliar places everyday, but it is probably the biggest use case for a nav system there is.


On Sep 9, 2014, at 1:17 PM, Martijn van Exel wrote:

> 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.

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