[talk-au] secondary_link

[Jack Burton]

On Sun, 2008-03-09 at 18:55 +1030, Darrin Smith wrote:
> I can tell you jack that they are 2-way roads, since I'm the one who's
> put them in there.

Ok, good. That's what I thought.

> Let me explain the reasoning behind my use of those tags (which upon
> reflection and the comment by Stuart earlier made me realise I've done
> it wrong, for which I apologise).
> 
> I use JOSM to edit the maps and I have the validator turned on. This
> causes those little bits of road to come us as invalid because they
> don't have a name. So I went looking for a way put the cross overs in
> those cases without having to enter the road name all the time (It just
> seemed redundant to enter the name of the road to shut up the validator
> for the sake of a few turn lanes.) I saw the motorway_link
> and primary_link entries which talk about 'slip lanes' to enter/exits
> roads, which seemed to fit for these cases. AT NO POINT in the easily
> accessible (or anywhere I've so far found) portions of the Wiki does it
> make it clear that those lanes are one way, so I assumed they just
> covered general entry/access road pieces.
> 
> So my question therefore becomes what DO you tag these roads with?????
> 
> I've found roads of secondary, tertiary and residential categories that
> effectively have _link level turn lanes in addition to central turning
> lanes. In the case of tertiary and residential I've just using the
> normal tags for all of them (and having to put the name of the road in
> on every case to shut up the validator & map lint) although I might
> have snuck a tertiary_link or two in around the place to be honest :)

Hmm, good point. I don't think just adding secondary_links into the
dataset alone will solve the problem though.

A quick fix could be to patch the validator, so it doesn't complain
about unnamed highway=secondary or highway=tertiary ways, so long as
they contain no more than say 3 nodes and have length of less than some
arbitrary cutoff (say, 15 metres?). That would fix the problem for
central turning lanes. But it wouldn't fix the problem altogether for
slip lanes, since many of these contain multiple nodes for smoothing and
can sometimes be as long as a short legitimate named road (and we
wouldn't want the validator ignoring them).

Having thought about it a bit now, I think secondary_link and probably
tertiary_link as well should be made valid values for the highway tag.
But we should probably introduce this as a proposed feature on the wiki
for a while before actually using them, hopefully getting at least the
main renderers to recognise them first.

I'm not sold on _link derivatives for highway=residential or
highway=unclassified though. If these have central turning lanes, they
should probably be upgraded to highway=tertiary anyway. Where
residential roads have slip lanes, they often have addresses on them
(cf. slip lanes on more major roads), so would need to verify which
street at the junction those addresses belong to (quick look at street
numbers for continuity should do the trick), then name the slip lane
accordingly.

As an alternative for use with highway=unclassified &
highway=residential, would tagging the slip lanes and/or central turning
lanes as highway=service be suitable?

What does everyone else think?

Regards,


Jack.