[Routing] [motorway_link] description of direction

[Jon Bright]

Nic Roets wrote:
> On Sun, Jun 15, 2008 at 1:35 PM, Jon Bright <jon at siliconcircus.com> wrote:
>> tag a given node for example as
>>
>> signpost=Dortmund, Münster
>>
>> Or
>>
>> signpost:1=Dortmund, Münster
>> signpost:2=Dortmund, Münster
>> signpost:3=Wuppertal, Köln
>> signpost:4=Sprockhövel
> 
> This is very motorway / motorcar specific. Many roads in Africa and on
> hiking trails are not signposted and can only be described by free
> form strings.

I don't really follow how "signpost" is motorcar or motorway-specific or 
why you couldn't add free-form strings there.  The numbers variant is 
multi-lane-road-specific, sure (I wouldn't want to describe it as 
car-specific, though, without taking a closer look at bike-centric 
places like Amsterdam...).

I should have probably added a third variant, signpost:left, 
signpost:right and signpost:straight, for normal T-Junctions or 
crossroads - be they on roads, cyclepaths, footpaths or African hiking 
trails.

> I propose that we either tag the destination way e.g. the
> motorway_link, or use 1 relation for each possible maneuver
> (from='source' to='dest'). It's up to the routing program to look
> ahead for signpost messages.

I don't mind adding relations, but looking ahead for signpost messages 
is a bad plan, imho.  Later signposts may be more (or less) specific 
about destination, or contain varying instructions.  In general, they 
may vary from an earlier signpost and therefore not be useful in that 
respect.

> Wuppertal can be tagged with "At the Acme junction, take the middle
> lane for the exit marked 'Wuppertal'". For messages fitting a certain
> layout, we can have machine translation into other languages e.g.
> using 'sed'.

If you're manually tagging, you're never going to get people to follow 
layouts strict enough to be sed-translateable.

-- 
Jon Bright
Silicon Circus Ltd.
http://www.siliconcircus.com