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KB10442 - Turn restrictions in DK routing operations.

The DK supports blocking specific turns in situations involving one-way or traffic-forbidden streets. So a left or right turn into the wrong direction on a one-way street can be restricted in the route calculation. These restrictions must be coded to the attributes of the line vectors (links) representing the street segments.

Beyond situations involving one-way streets, the DK does not support the assignment of turn restrictions and turn "costs" to the actual intersection nodes. Because the DK is grounded on the concept of intersection nodes, however, a DK developer can customize the DK to support node based turn restrictions. (Or TatukGIS could be hired to develop this functionality). In order to program costs/restrictions directly to the turn itself, the DK would need to be modified so as to consider the spatial relationship between two touching links and the “history” along the route. As an example, the program would need to recognize that a given route involves a course first via node 56 to node 57 and then to node 588, and recognize from the spatial relationships of vector segment 56-57 and vector segment 57-588 that such route involves a left turn. Then the restriction or cost factor could be assigned to that situation by appropriately coding the cost information to the attributes of the vector line segments involved.

Refer to KB10444 for more on coding on-way streets and KB10681 for general information on DK optimal routing.

Created: November 21, 2003, Modified: November 03, 2015