[OSM-talk] [tagging] RFC :left/:right (asymmetrical roadside features)

Dave Stubbs osm.list at randomjunk.co.uk
Tue Feb 17 11:43:15 GMT 2009

2009/2/17 Andy Allan <gravitystorm at gmail.com>:
> On Mon, Feb 16, 2009 at 7:11 PM, Norbert Hoffmann
> <nhoffmann at spamfence.net> wrote:
>> Andy Allan wrote:
>>>And every time using :left and :right comes up, we all have a big
>>>discussion about it and then nobody pays any attention and it comes up
>>>again a few months later.
>> Perhaps this is because the concept "left"<>"right" is so simple - and the
>> aversion against editors, that are not totally key-ignorant is not so easy
>> to understand.
> And nobody pays attention. The main problem is that two-way roads have
> no inherent, real-world, "direction" - neither side of the road is the
> right or the left. Or rather, both sides of the road are the right or
> the left, depending on which way you are facing. The only place that
> right and left has any intrinsic sense is on one-way roads, which *do*
> have an inherent direction (and signs to that effect).
> Let's say you have a church beside a road. If it's a oneway street, it
> makes some kind of sense to say "it's halfway along the road, over on
> the left".
> Let's say you have a church beside a two-way road. If I said "it's
> halfway along the road, over on the right", you still wouldn't know
> which side of the road it is on.
> Now the problem is that most people at the moment in OpenStreetMap are
> tech-heads, and are so used to mental constructs and abstractions like
> every road having a completely arbitrary intrinsic direction - but
> that doesn't mean it's a great idea. Editor support is less important
> - and far easier to fix - than explaining to all the people who don't
> even realise that all roads have a direction in openstreetmap - and
> except for oneway roads, I have no idea which ways are pointing in
> which directions, and it shouldn't be important unless it *has* to be
> important.

Of course you expect any decent editor to solve the problem by letting
the user choose which side of the way to apply the feature to. It
really doesn't matter what the tagging is, the editor will have to
solve the UI problem in almost exactly the same way.

The only way of avoiding this issue in some non-confusing way is to
not use tagging as the answer. Some complex relation with a "this
side" member which still needs editor support. Or just adding another
way to the database for each left/right feature, which becomes hard
when you try to connect things together.

The reason this gets ignored is because it's hard, and most solutions
don't work for normal people without editor support, and our editors
don't support it. Plus every time someone comes up with a solution,
everybody points out the problems with it, which mostly seem to be
worrying about the data being accidentally corrupted (ie: reversing
ways), or not being easy for newbies/non-techies. And that's true for
just about any method of entering data that isn't simple.


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