[Routing] [motorway_link] description of direction

[Nic Roets]

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 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.

We need 2 sets of instructions :
* Freeform instructions that will typically be produced by a website
or non-gps device. For example the motorway_link that goes to
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'.
* A message from a predetermined set that can easily be turned into
audible instructions on a resource poor GPS. The tag must also encode
the distance before the intersection that the instructions must be
played. It can even be a set of instructions e.g. "200m
StayInMiddleLane; 100m StayInLeftLane; 50 JoinMotorway"