[Tagging] turn:lanes vs. turnlanes:turn

Ronnie Soak chaoschaos0909 at googlemail.com
Thu Oct 17 07:28:09 UTC 2013


I'm in the process of adding more detail to the major junctions in terms of
lane counts, turn lanes, width, etc.

There seem to be two tagging schemes in parallel:

- the turn:lanes[1] scheme which adds lane descriptions as tags to way
- the turnlanes:turn[2] scheme which adds lane connections via relations to
the junction nodes

They don't mach exactly in the kind of information the record. The
turn:lanes scheme describes the lanes and lane markings leading to the
junction (with only fuzzy information on where the lanes lead). The
turnlanes:turn relation then describes how each lane is connected to an
outgoing direction (without stating how they are marked).

But they also encode the same information in two ways, for example the
length of the turn lanes (by way segment length with turn:lanes, as
numerical tag value with turnlanes:turn).

Both are nicely supported by a JOSM style (turn"lanes) [3] and a JOSM
plugin (turnlanes:turn).

According to taginfo, turn:lanes is used approx. 47k times, turnlanes:turn
is used approx. 10k times.

I personally don't like the turnlanes:turn scheme very much because it
introduces quite a lot of extra relations per junction which probably make
it less maintainable then tag-based schemes or a
single-relation-per-junction scheme, but that is more a question of taste
than anything.
This topic was briefly discussed already on the German and Austrian
talk-lists with mostly the opinion to use the newer and more elegant
turn:lanes scheme. But I see no easy way of enhancing the turn:lanes scheme
to include the missing connection information without bloating it up and
making it unusable.

So my questions:
- Are these schemes both still actively used? Are there data consumers who
use these already?
- What are the pros and cons of using them both in parallel?
- Are there better ways of getting *all* of the information across without
the redundancy introduced by using both schemes?


[1] http://wiki.openstreetmap.org/wiki/Key:turn:lanes
[2] http://wiki.openstreetmap.org/wiki/Relations/Proposed/turn_lanes
[3]  http://josm.openstreetmap.de/wiki/Styles/Lane_and_Road_Attributes
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