[OSM-talk] SOTM relations workshop: results

Ben Laenen benlaenen at gmail.com
Thu Aug 21 12:14:42 BST 2008


On Wednesday 20 August 2008, Frederik Ramm wrote:
> Routes
> ------
>
> Routes are most prominently used for cycle routes which are rendered
> on Andy Allan's cyclemap. Generally ways which are part of a route
> don't have a role, they're just part of it. But sometimes you have
> ways in the roles "forward" and "backward", and I had thought that
> these refer to different routings used by, say, a bus at it goes in
> one direction and back again. Turns out that the "forward" and
> "backward" are only meant clarify how the route goes by saying "you
> have to turn this way around to match up with the direction of the
> others", and can often be ignored.

Er... I have no idea what you actually mean by that last sentence, but I 
think your original thought was more correct. Forward meaning that the 
route follows only the direction of the way, backward meaning that the 
route follows the opposite direction of the way, and no role means that 
the route goes in both ways along the road.

Example: (---> is a way, with direction shown by arrow)

    
A ----> B <---- C -----> D

if I have a oneway route from A to D, then the role for ways AB and CD 
will be forward, and for way BC it's backward.

If the route goes both ways between A and D, the ways have no roles.

A ----> B <---- C -----> D
        |       |
        v       v
        E ----> F

If in this example the route goes from A to D via ABEFCD and the route 
goes from D to A via DCBA, the roles are as follows:
AB, CD: no role
BC, BE, EF: forward
CF: backward

Greetings
Ben




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