[OSM-talk] Next: Relation name (WAS: Removing redundant routing instructions)

Lester Caine lester at lsces.co.uk
Tue Apr 28 12:23:44 UTC 2015

On 27/04/15 21:31, Rob Nickerson wrote:
> Ok a few people are agreeing that a relation is needed to assist the
> routing engine to provide higher quality instructions (with routing left
> unaffected). That's good.
> I'd like to get something in the wiki and ideally get it approved (this
> is not an invite to talk about the wiki or the approval process - I've
> heard it all before).
> Question: Should I revive the "through_route" proposal or start a new
> one under a different name, say "route_continues" (or just "continues")
> so as to avoid any ambiguity with the use of "through route" in general
> language?

Reading the objections on
http://wiki.openstreetmap.org/wiki/Proposed_features/through_route and
to be honest, the example used is simply wrong. Since AC and DC are both
'A56' then there is nothing additional needed. That routing software
does not use the clean information in this case is not an OSM problem?
Now if you want to tell the router that the 'main' route goes onto the
other road that is a different problem? That the junction has a 'stop'
when going from A to D is not unusual, with B->D having priority. That
should be distinguishable if the correct junction tagging is applied?

I was looking at the actual problem which only occurs when there is not
a matching road segment either side of the junction. We do have the
problem of not having reliable identification tags, but if we are
working with road segments which have a usable ID, be that a 'ref' or
second a road name, then this information is cleanly tagged on all three
legs on the example. To my mind, the 'through_route' tag is also applied
to those segments rather than the junction, so we have ... for example
... name=LondonRoad, through_route=OxfordWay and the reverse on the
other side. The routing software then knows the primary route through
the junction and can announce as appropriate.

For unidentified roads, which is one of my irritations around this area,
one needs a way of identifying the two ways which is not then also
displayed. One of those places where 'object_id' could be useful, but to
be honest I think one simply lives with the 'strange' messages. I don't
think that things like trying to create a relation are productive.
Although in the UK if the street gazetteer data becomes freely usable
then there will be id's that can be used after reference and name.

Lester Caine - G8HFL
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