[Potlatch-dev] [OpenStreetMap] #3567: Add ability to create a no_u_turn restriction with a way "via"

[OpenStreetMap]

#3567: Add ability to create a no_u_turn restriction with a way "via"
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 Reporter:  ponzu        |       Owner:  potlatch-dev@…                
     Type:  enhancement  |      Status:  new                           
 Priority:  major        |   Milestone:                                
Component:  potlatch2    |     Version:                                
 Keywords:               |  
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Comment(by ponzu):

 Certainly: http://osm.org/go/TPVwL_aE5--   There are no U turns allowed at
 the intersection of Enterprise and Parker Place. Therefore, four
 turn_restriction relations are required. Because both Enterprise and
 Parker Place are drawn as divided roads, it is meaningless to used the
 nodes as the "via" members. The routing algorithms will ignore such
 restrictions because they will consider each maneuver in question to be a
 left turn onto the cross-street rather than a U turn. At the same time, it
 will not do to add left turn restrictions, because left turns are, of
 course, permitted. I was told in the Help forum that using the short
 section of the cross street as the "via" member does the trick and the
 routing algorithms respect it.  I personally have not had a chance to
 verify this theory because CloudMade takes forever to accommodate the OSM
 changes and this particular intersection still looks as it was 2 weeks ago
 before I added  the restrictions. But I assume the person who gave this
 advice knows what he is talking about. Now if only it was as easy to
 create such restrictions as it is to create them when the "via" member is
 a node.

 Here's the original discussion:
 http://help.openstreetmap.org/questions/3530/what-is-the-proper-way-to-
 add-no-u-turn-restrictions-when-the-road-is-divided

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Ticket URL: <https://trac.openstreetmap.org/ticket/3567#comment:3>
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