[OSM-talk] [Talk-us] Am I mapping this wrong, or should the router be fixed for this?

Colin Smale colin.smale at xs4all.nl
Thu Jul 30 19:24:12 UTC 2015


I assume you are talking about typical speeds, and not a practical maximum. A max speed will almost never be achieved, by definition actually as the vehicle speeds will have a certain distribution. The highest recorded speed will be the de facto practical maximum, assuming the driver survived.
Routers could take account of hundreds of variables in their calculation of predicted journey time from A to B, but in practice their calculations make assumptions for most of them. For example, most of them assume the vehicle is a car, that it is technically not limited to any particular speed, that the weather is perfect, that it is daytime, that the driver is not "inexperienced". And then there are the other volatile variables like traffic density, road works, oversize loads getting in the way etc.
Routers cannot take everything into account (this would preclude a lot of preprocessing to simplify the real-time calculations), so they use heuristics which work most often.
So how would you define the concept of "typical speed"?
--colin


On 30 July 2015 20:38:32 CEST, Richard <ricoz.osm at gmail.com> wrote:
>On Thu, Jul 30, 2015 at 08:00:55PM +0200, Colin Smale wrote:
>> Practical maxspeed is useless as well. A straight wide road may be
>capable of hosting land speed records, but traffic density is likely to
>be a far more important factor.
>
>yes, and this is what practical maxspeed is good for. Not 
>an ideal solution but works.
>
>Richard
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