[GraphHopper] turn restrictions

[Bruno Carle]

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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