[GraphHopper] turn restrictions

[Peter]

ah, yes. If there is a one-way network around the restriction a failed
route for '1dir' is a lot more likely. So maybe we remove this option
entirely as it now does not look that good anymore for me in real world.

The best thing would be if we could create a hybrid solution. Doing
'1dir' for areas with no restrictions and '2dir' for the other areas
which are a lot less likely. This way we would have same speed as
node-based traversal but with correct routes. There is a paper for this
hybrid but we probably have to keep it simple for now ...

> For our own usage I think we would not use EDGE_BASED_2DIR_UTURN
because, the u turn are mainly for the via points

I also do not like the routes it produces and also forbidden u-turns are
not that often tagged and so it produces forbidden routes. So yes, maybe
we remove this option also and instead make an u-turn option available
for the via-points. If you have some code for this please do not
hesitate to contribute :)

Regards,
Peter.

On 22.08.2014 09:57, Bruno Carle wrote:
> Hi Peter,
> In the namesti miru example the path will not be found, even using the
> full city map, this is because the northest part of the Varsavska
> street is only accessible thru easter part of Uruguaska,
> which is in only accessible from Francouska driving south/east. For
> the map see
> https://graphhopper.com/maps/?point=50.074831%2C14.439039&point=50.07333%2C14.43869 
> and http://imgur.com/MftaocZ
>
>
> I will run later against a batch of usage routes from our prod and let
> you know how often it happens.
>
> Regarding u turn, 0-1-2-1-6 would not be allowed in this namesti miru
> example (the node 2 beeing where Francouska  joins Namesti Miru),
> For our own usage I think we would not use EDGE_BASED_2DIR_UTURN
> because, the u turn are mainly for the via points (i.e. after
> picking/dropping a delivery), and we do not use GH' via points,
> instead we perform several point to point requests,
> so u turns in this case are automatically covered by the query graph.
>
> My feeling is that  often  EDGE_BASED_2DIR_UTURN, will produce routes
> with u turns which are not allowed.  Again I will run against some
> batch and let you know how often it happens.
>
> Regards
> Bruno
>
>
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