[Routing] Turn restrictions

Nic Roets nroets at gmail.com
Wed Aug 13 13:14:38 BST 2008

Gosmore now supports basic turn restrictions. When there is only one
member in the 'via' role namely the node. no_left_turn is interpreted
to mean a turn of more than 45 degrees, but less than 135 degrees to
the left. Similar assumptions are used for all the other directions.
Furthermore, no_left_turn is most of the time the same as

Gosmore does not try to make a u-turn at each node, back into the same
way. So I've done a test where a restriction forced it to left when it
wanted to go right, and it then needed to make an elaborate journey
just to turn the car around. In practice, turn restrictions only occur
where there are nearby alternatives.

It may take some time for Lambertus to update his site, so I can't
give you a web demo yet.

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