[OSM-talk] Turn restriction docs

Erik Johansson erjohan at gmail.com
Sat Nov 29 14:06:50 GMT 2008


I've been looking at the 100 or so turn restrictions[1] in use, and
most of them don't follow the spec set up on the wiki making the
description very confusing. Considering how complicated relations
feels I'm asking here instead of just changing the wiki:
http://wiki.openstreetmap.org/wiki/Relation:restriction

So in the scheme *in use* today you say "no left turn, to:way2
from:way1", and then in the routing programs/rendering applications
need to calculate what that means. I think this makes the "via this
node" irrelevant as long as the ways share only one node.

I also think Gosmore is doing these calculations, to check for
left/right turns, not quite sure though


[1]
## number of restriction relations
curl -s 'http://www.openstreetmap.org/api/0.5/relations/search?type=type&value=restriction'|tee
restrictions |grep 'v="restr' |wc
     100     300    3600


sed '/k="rest/!d;  s/.*v="\([^"]*\).*/\1/;' restrictions | sort | uniq
-c | sort -nr
  57 no_right_turn
  25 no_left_turn
   6 only_right_turn
   2 only_straight_on
   2 no_turn_left
   1 only_left_turn
   1 no_u_turn
   1 no_straight_on


## number of relations with more than one via node
sed 's/.*<relation.*/relation/;s/.*role="via".*/via/;
t
d' restrictions |uniq -c|grep -v 1|grep via|wc -l
0




More information about the talk mailing list