[OSRM-talk] Blocking zones in OSM

[Frederik Ramm]

Or, what Julien said ;)

On 26.08.20 10:31, Frederik Ramm wrote:
> Hi,
> 
> On 26.08.20 03:29, Alex Valencia wrote:
>>   So I was thinking if there is a proper way to achieve this goal. We
>> are considering separating the matrix calculation over the map in a
>> separate function and feeding it with a decorated version of the
>> original map where we can remove these regions on the fly prior to the
>> calculation. But I'm also not sure if this is a realistic way either.
> 
> The only routing package I know that does polygonal avoid areas out of
> the box is OpenRouteService which internally is powered by a modified
> version of GraphHopper. However, only the simple route request supports
> avoid areas, not the matrix request, and it's only available if you use
> basic A*.
> 
> Using avoid areas with Contraction Hierarchies is impossible unless the
> avoid areas are baked into the graph (i.e. known at graph building
> time). If your avoid areas *are* known at graph building time then
> actually removing edges from the OSM data (or doing so while reading it
> into OSRM) is certainly option that gives you the fastest routing speed.
> 
> If you want to use OSRM, and if you want to use dynamic avoid areas,
> then this *might* be possible with a MLD routing graph which has the
> option of changing the weighting of certain edges without re-generating
> the graph; this was implemented to allow for live traffic (search for
> "osrm traffic" and you'll find some stuff about it, using
> osrm-customize). However this still requires you to identify the edges
> you wish to cut off (by giving them a zero rating), and it is only
> possible globally and not on a per-request basis (unlike
> OpenRouteService which lets you set avoid areas per-request).
> 
> If you have a number of pre-defined avoid areas and want to determine
> dynamically which of these should be avoided then it might be possible
> to abuse a feature that was built to avoid certain road classes (i.e.
> avoid motorways, avoid ferries); potentially you could use that to
> define a specific road class for all roads in your avoid area A, a
> different class for avoid area B etc., and then make a routing request
> that "avoids class A". This feature is documented here
> https://github.com/Project-OSRM/osrm-backend/issues/4006
> 
> Bye
> Frederik
> 

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"