[OSM-talk] average speed as opposed to speed limit in calculating routes

[Peter Wendorff]

Hi Renato.

I think we had a similar discussions some time ago on one of the mailing 
lists, but I don't find it currently.

Some thoughts about it:

1) possibilities to do sth. like that in OSM:
Waze uses recorded data collections from real users. Provided that these 
are real users and real traces, the speed estimation cannot be 
manipulated by anyone, and can be calculated from a big database by 
algorithms. This is not possible (or at least useful) in osm: what is 
the average speed of a particular road? at which time of the day? during 
holidays? at the weekend? by motorcycle or truck? .....
It might be possible to get an incredible complex tagging scheme for 
that - but you need a huge amount of data to be added and maintained to 
get useful data from it, so it's nothing for by-hand-work of mappers IMHO.

2) problems of manipulations:
Living at a big street people often don't want to have more traffic in 
front of their sleeping room window than necessary. A legal speed limit 
is a fact - you can proove it's correctness and lying about it is "more 
difficult" and detected as vandalism if you keep wrong facts there.
But an average speed is hard to measure, even harder to proove, and 
dropping it by 20km/h may lead an important router to use a different 
route - great; but there's no benefit to the user of that router, 
because driving there at night or only outside the rush hours he might 
have omitted the traffic jams, so the shorter route in fact may have 
been much faster.

On top of that these data often change fast with construction sites, 
special events, holidays and much more.

To summarize: I can imagine a system similar to waze collecting traces 
and statistical data about average speed, and I can imagine osm based 
routers that take this into account; but I don't think it's 
possible/manageable to include this kind of data to the osm database itself.

regards
Peter

Am 26.08.2012 11:41, schrieb renato:
> Hi, I've been trying out the Waze android GPS navigator and the one
> feature I really find useful of it is that, in route calculation, it
> doesn't use the road speed limit but rather the actual average speed on
> that road, calculated from the data gathered from other users driving
> those roads.
>
> In a few days of use, I have discovered some new routes for places I
> regularly go to, routes that are less known but certainly faster (avoid
> traffic lights for example). Also the time estimates are way better
> than Osmand (the only OSM navigator I actively used, but I plan on
> trying other ones).
>
> Could something like this be done in OSM? Has someone ever thought of
> it? First thought would be an average_speed_by_car tag, that navigators
> could use in calculating routes. Even better would be an automated way
> of updating these tags by users using the navigator.
>
> just curious to know thoughts about this idea,
>
> cheers
> renato
>
>
>
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