[Openstreetmap] Re: key values to represent restricted turns

[Andy Robinson]

I was looking at this by keeping only reference to the nodes.

Simple example:

1  2  3
*--*--*
   |
   *4

If travel from node 1-2-3 is permissible but from 1, no turn at 2 is
permissible to go to 4, ie 1-2-4 is not permissible.

Routing picks up the nodes for segment 1-2. The properties for node 2
include an overide that disallows connection to 4, so the segment 2-4 is not
available for routing. Where the restriction varies between mode of
transport or time of day the overide would be conditional.

Does this approach work, noting the offline editing issues? Does it work
also for restricting the direction of flow between two points as well?

Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: openstreetmap-bounces at vr.ucl.ac.uk [mailto:openstreetmap-
>bounces at vr.ucl.ac.uk] On Behalf Of Simon Hewison
>Sent: 25 January 2006 17:10
>To: openstreetmap at vr.ucl.ac.uk
>Subject: Re: [Openstreetmap] Re: key values to represent restricted turns
>
>Gabriel Ebner wrote:
>> On Mon, Jan 23, 2006 at 08:27:54PM +0000, Tom Carden wrote:
>>> How about something like a property on a node like
>>> no-turn=a.b,c.e,e.d; where a/b/c/d/e are segment ids for segments
>>> connected to that node, and order matters?  All other combinations are
>>> fair game for routing.
>>
>> Can we have that on segments too?
>>
>> E.g. there are some junctions (in Austria, at least) where you can drive
>from
>> A to B but not from C to B:
>>
>>           |
>>           C
>>           |
>>      --D--+--B--
>>           |
>>           A
>>           |
>
>Restriction on the approach segment could work, but I don't like the
>idea of using segment IDs, for a start, it makes offline editing
>impossible, since the segment ID would not be available until it's been
>committed. Segment names are easy for everyone to keep up with.
>
>If we reffered to segment names instead, that could work, so in the
>above example, both B and D could be named "Billy Street", and A and C
>could be named "Alfred Street"
>
>given the above example, y
>
>On segment C, you could have "no-left-turn=Billy Street", and that's the
>only place where the restriction needs to be. Obviously, you could turn
>right onto Billy Street (segment D), and all other turns permitted.
>
>even on a more complex situation, this could work
>
>         |
>         C
>         |
>-----D--+--B----
>         |\
>         | E
>         A
>
>with the above rule, C-B is forbidden, but C-E is permitted, because
>despite it being a left turn, the name of segment E is not listed. If it
>was also forbidden, you could define segment E as "Edgar Street" and then:
>
>no-left-turn=Billy Street,Edgar Street
>
>but C-D is permitted (even though it is Billy Street) because it's not a
>left turn, it's a right turn.
>
>This also makes the tags easy for both humans and machines to read.
>--
>Simon Hewison
>
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